implementation

Practice › Codeforces Solutions ›

Codeforces Round 1091 (Div. 2) and CodeCraft 26

Codeforces Round 1091 (Div. 2) and CodeCraft 26 Type: Div. 2 | Problems: 4 | Verified: 0/4 | Rating range: 1000-2600 | Time: 7m 34s Problem Name Rating Tags Solve Time Verified B Flip the Bit (Easy Version) 1000 greedy, implementation 2m 15s ✗ D Flip the Bit (Hard Version) 1900 greedy, implementation, math 1m 50s ✗ E Definitely Larger 2000 binary-search, constructive-algorithms, data-structures 1m 39s ✗ G Down the...

Practice › Codeforces Solutions › Codeforces Round 1091 (Div. 2) and CodeCraft 26 ›

CF 2217D - Flip the Bit (Hard Version)

CF 2217D - Flip the Bit (Hard Version) Rating: 1900 Tags: greedy, implementation, math Solve time: 1m 50s Verified: no Solution Problem Understanding We are given a binary array where each position contains either 0 or 1. A subset of positions is marked as special, and all special positions initially share the same value, call it $x$. The goal is to transform the entire array so that every element becomes...

Practice › Codeforces Solutions › Codeforces Round 1091 (Div. 2) and CodeCraft 26 ›

CF 2217B - Flip the Bit (Easy Version)

CF 2217B - Flip the Bit (Easy Version) Rating: 1000 Tags: greedy, implementation Solve time: 2m 15s Verified: no Solution Problem Understanding We are given a binary array of length n and a single special index p (since k=1 in this easy version). The bit at this index is considered "correct," and the goal is to make the entire array equal to this bit by performing the fewest number of...

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April Fools Day Contest

April Fools Day Contest Type: April Fools | Problems: 8 | Verified: 8/8 | Rating range: 1200-2000 | Time: 13m 15s Problem Name Rating Tags Solve Time Verified A Mysterious numbers - 1 1200 *special, constructive-algorithms 1m 43s ✓ B Star 1300 *special, combinatorics 2m 57s ✓ C A Piece of Cake 2000 *special, implementation 1m 30s ✓ D Broken checker 1300 *special, brute-force 1m 14s ✓ E MYSTERIOUS LANGUAGE...

Practice › Codeforces Solutions › April Fools Day Contest ›

CF 171H - A polyline

CF 171H - A polyline Rating: 1700 Tags: *special, implementation Solve time: 1m 39s Verified: yes Solution Problem Understanding The input contains two numbers. The first number, a , determines the order of a recursively constructed polyline. The second number, b , is an index along that polyline. The picture in the statement is the key. It is the classical Hilbert curve, a space-filling curve that visits every cell of...

Practice › Codeforces Solutions › April Fools Day Contest ›

CF 171F - ucyhf

CF 171F - ucyhf Rating: 1600 Tags: *special, brute force, implementation, number theory Solve time: 1m 11s Verified: yes Solution Problem Understanding We are asked to find a special number associated with a single integer input d , where d represents a divisor or parameter in a number-theoretic sequence. The output is another integer computed from d according to a hidden mathematical rule, likely involving divisibility, modular arithmetic, or a...

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Codeforces Round 1090 (Div. 4)

Codeforces Round 1090 (Div. 4) Type: Div. 4 | Problems: 4 | Verified: 1/4 | Rating range: 800-1800 | Time: 10m 7s Problem Name Rating Tags Solve Time Verified A The 67th Integer Problem 800 brute-force, games, implementation 1m 27s ✓ D The 67th OEIS Problem 1100 constructive-algorithms, greedy, math 2m 4s ✗ F The 67th Tree Problem 1500 constructive-algorithms, implementation, trees 3m 38s ✗ G [The 67th Iteration of...

Practice › Codeforces Solutions › Codeforces Round 1090 (Div. 4) ›

CF 2218F - The 67th Tree Problem

CF 2218F - The 67th Tree Problem Rating: 1500 Tags: constructive algorithms, implementation, trees Solve time: 3m 38s Verified: no Solution Problem Understanding We are asked to build a rooted tree with exactly $n = x + y$ vertices. The root is fixed to be vertex $1$. For every vertex, consider the size of its rooted subtree. A vertex is counted in the "even" group if its subtree contains an...

Practice › Codeforces Solutions › Codeforces Round 1090 (Div. 4) ›

CF 2218A - The 67th Integer Problem

CF 2218A - The 67th Integer Problem Rating: 800 Tags: brute force, games, implementation, math Solve time: 1m 27s Verified: yes Solution Problem Understanding The problem asks us to pick an integer $y$ for a given integer $x$ so that the minimum of $x$ and $y$ is as large as possible. We are given multiple test cases, each consisting of a single integer $x$ between -67 and 67. Our output...

Practice › Codeforces Solutions › Codeforces Round 114 (Div. 2) ›

CF 168A - Wizards and Demonstration

CF 168A - Wizards and Demonstration Rating: 900 Tags: implementation, math Solve time: 2m 1s Verified: yes Solution Problem Understanding The city has n real residents. Among them, exactly x are wizards, and all of those wizards will attend a demonstration. Nobody else will attend. The administration measures attendance as a percentage of the real city population, which remains n even if the wizards create clones. A clone counts as...

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Codeforces Round 114 (Div. 2)

Codeforces Round 114 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 900-900 | Time: 2m 1s Problem Name Rating Tags Solve Time Verified A Wizards and Demonstration 900 implementation, math 2m 1s ✓

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Codeforces Beta Round 81

Codeforces Beta Round 81 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1700-2700 | Time: 13m 32s Problem Name Rating Tags Solve Time Verified A Transmigration 1700 implementation 3m 6s ✓ B Dark Assembly 1800 brute-force, probabilities 2m 19s ✓ C Item World 2200 brute-force, implementation, sortings 3m 26s ✗ D Entertaining Geodetics 2700 brute-force, dsu, implementation 2m 8s ✓ E Lift and Throw 2500 brute-force 2m...

Practice › Codeforces Solutions › Codeforces Round 1095 (Div. 2) ›

CF 2226G - Stop Spot

CF 2226G - Stop Spot Rating: - Tags: implementation, strings, trees Solve time: 2m 32s Verified: no Solution Problem Understanding An array $a$ is fixed, and we append to it a permutation $p$ of ${1,2,\dots,m}$ to form a longer array $b_p$. For each such permutation, we count how many subarrays of $b_p$ with even length are palindromes. This produces a value $i$, and over all permutations we define $f(i)$ as...

Practice › Codeforces Solutions › Codeforces Round 1096 (Div. 3) ›

CF 2227D - Palindromex

CF 2227D - Palindromex Rating: - Tags: binary search, brute force, constructive algorithms, data structures, greedy, implementation, two pointers Solve time: 3m 24s Verified: no Solution Problem Understanding We are given an array of length $2n$. Every value from $0$ to $n-1$ appears exactly twice. The task is to select a contiguous segment of this array that reads the same left-to-right and right-to-left, and among all such segments we want...

Practice › Codeforces Solutions › Codeforces Round 1096 (Div. 3) ›

CF 2227A - Koshary

CF 2227A - Koshary Rating: - Tags: implementation, math Solve time: 2m 38s Verified: no Solution Problem Understanding We are given a grid starting at the origin point $(0,0)$ and a target point $(x,y)$. At each move, Yousef can increase exactly one coordinate by 2 using a long step, either moving right by 2 or up by 2. In addition, he is allowed to use a single special move during...

Practice › Codeforces Solutions › Codeforces Beta Round 81 ›

CF 105D - Entertaining Geodetics

CF 105D - Entertaining Geodetics Rating: 2700 Tags: brute force, dsu, implementation Solve time: 2m 8s Verified: yes Solution Problem Understanding The statement is intentionally wrapped in game terminology, but the underlying process is a sequence of color merges. Each map cell has a panel color. Some cells also contain a symbol, and every symbol has its own color. We start by destroying one specific symbol. Destroyed symbols are processed...

Practice › Codeforces Solutions ›

Codeforces Round 1096 (Div. 3)

Codeforces Round 1096 (Div. 3) Type: Div. 3 | Problems: 8 | Verified: 0/8 | Rating range: - | Time: 27m 59s Problem Name Rating Tags Solve Time Verified A Koshary - implementation, math 2m 38s ✗ B Party Monster - greedy 3m 38s ✗ C Snowfall - constructive-algorithms, math 4m 24s ✗ D Palindromex - binary-search, brute-force, constructive-algorithms 3m 24s ✗ E It All Went Sideways - binary-search, data-structures,...

Practice › Codeforces Solutions › Codeforces Beta Round 81 ›

CF 105A - Transmigration

CF 105A - Transmigration Rating: 1700 Tags: implementation Solve time: 3m 6s Verified: yes Solution Problem Understanding The problem simulates a single transmigration process in a role-playing game. We start with a character who already possesses several skills. Each skill has a name and an experience level. When transmigration occurs, every existing skill has its level reduced by a coefficient k . The new level becomes the integer part of...

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Codeforces Round 282 (Div. 2)

Codeforces Round 282 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 1100-1600 | Time: 7m 5s Problem Name Rating Tags Solve Time Verified A Digital Counter 1100 implementation 1m 39s ✓ B Modular Equations 1600 math, number-theory 5m 26s ✗

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Codeforces Round 279 (Div. 2)

Codeforces Round 279 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 0/5 | Rating range: 1500-2200 | Time: 44m 5s Problem Name Rating Tags Solve Time Verified B Queue 1500 dsu, implementation 11m 48s ✗ C Hacking Cypher 1700 brute-force, math, number-theory 5m 25s ✗ D Chocolate 1900 brute-force, dfs-and-similar, math 5m 18s ✗ E Restoring Increasing Sequence 2000 binary-search, brute-force, greedy 10m 45s ✗ F Treeland Tour...

Practice › Codeforces Solutions › Codeforces Round 945 (Div. 2) ›

CF 1973F - Maximum GCD Sum Queries

CF 1973F - Maximum GCD Sum Queries Rating: 3100 Tags: bitmasks, brute force, dp, implementation, number theory Solve time: 5m 16s Verified: no Solution

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Codeforces Round 275 (Div. 2)

Codeforces Round 275 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 0/2 | Rating range: 1100-1800 | Time: 16m 14s Problem Name Rating Tags Solve Time Verified A Counterexample 1100 brute-force, implementation, math 10m 52s ✗ B Friends and Presents 1800 binary-search, math 5m 22s ✗

Practice › Codeforces Solutions › Codeforces Round 946 (Div. 3) ›

CF 1974B - Symmetric Encoding

CF 1974B - Symmetric Encoding Rating: 800 Tags: implementation, sortings, strings Solve time: 5m 18s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 278 (Div. 1) ›

CF 487A - Fight the Monster

CF 487A - Fight the Monster Rating: 1800 Tags: binary search, brute force, implementation Solve time: 5m 21s Verified: no Solution

Practice › Codeforces Solutions ›

Codeforces Round 942 (Div. 1)

Codeforces Round 942 (Div. 1) Type: Div. 1 | Problems: 8 | Verified: 1/8 | Rating range: 1400-3500 | Time: 10m 27s Problem Name Rating Tags Solve Time Verified A Permutation Counting 1400 binary-search, greedy, implementation 1m 16s ✗ B1 Reverse Card (Easy Version) 1400 brute-force, math, number-theory 57s ✗ B2 Reverse Card (Hard Version) 2200 brute-force, math, number-theory 1m 30s ✗ C Fenwick Tree 2300 bitmasks, brute-force, combinatorics 1m...

Practice › Codeforces Solutions › Codeforces Round 281 (Div. 2) ›

CF 493A - Vasya and Football

CF 493A - Vasya and Football Rating: 1300 Tags: implementation Solve time: 1m 38s Verified: yes Solution Problem Understanding We are given the names of the home and away teams, followed by a chronological list of card events during a football match. Each event specifies the minute, which team the player belongs to, the player's jersey number, and whether the referee gives a yellow card or a red card. A...

Practice › Codeforces Solutions › Educational Codeforces Round 166 (Rated for Div. 2) ›

CF 1976D - Invertible Bracket Sequences

CF 1976D - Invertible Bracket Sequences Rating: 2000 Tags: binary search, combinatorics, data structures, divide and conquer, implementation, two pointers Solve time: 5m 14s Verified: no Solution

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Codeforces Round 941 (Div. 2)

Codeforces Round 941 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 0/2 | Rating range: 800-1100 | Time: 2m 20s Problem Name Rating Tags Solve Time Verified A Card Exchange 800 constructive-algorithms, games, greedy 1m 12s ✗ B Rectangle Filling 1100 constructive-algorithms, implementation 1m 8s ✗

Practice › Codeforces Solutions › Educational Codeforces Round 164 (Rated for Div. 2) ›

CF 1954B - Make It Ugly

CF 1954B - Make It Ugly Rating: 1200 Tags: implementation, math Solve time: 1m 15s Verified: no Solution Problem Understanding We are given an array of integers that is guaranteed to be "beautiful," which means that through a specific operation, all elements can eventually become the same. The operation allows us to pick any element that is not at the boundary and replace it with its neighboring value if the...

Practice › Codeforces Solutions › Codeforces Global Round 25 ›

CF 1951E - No Palindromes

CF 1951E - No Palindromes Rating: 2000 Tags: brute force, constructive algorithms, divide and conquer, greedy, hashing, implementation, math, strings Solve time: 1m 1s Verified: no Solution Problem Understanding We are given a string and we are allowed to cut it into contiguous pieces. The goal is to decide whether we can cut it so that every resulting piece is not a palindrome. If it is possible, we must also...

Practice › Codeforces Solutions › Codeforces Round 945 (Div. 2) ›

CF 1973C - Cat, Fox and Double Maximum

CF 1973C - Cat, Fox and Double Maximum Rating: 1700 Tags: constructive algorithms, greedy, implementation, math, sortings Solve time: 5m 15s Verified: no Solution

Practice › Codeforces Solutions › Educational Codeforces Round 164 (Rated for Div. 2) ›

CF 1954E - Chain Reaction

CF 1954E - Chain Reaction Rating: 2200 Tags: binary search, data structures, dsu, greedy, implementation, math, number theory Solve time: 1m 12s Verified: no Solution Problem Understanding We are given a line of monsters, each with some initial health. One operation consists of choosing a single monster as the starting point of a “chain lightning”. That lightning hits the chosen monster and then continues outward to both sides, always staying...

Practice › Codeforces Solutions › Educational Codeforces Round 166 (Rated for Div. 2) ›

CF 1976C - Job Interview

CF 1976C - Job Interview Rating: 1600 Tags: binary search, dp, greedy, implementation, two pointers Solve time: 5m 16s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 939 (Div. 2) ›

CF 1956E1 - Nene vs. Monsters (Easy Version)

CF 1956E1 - Nene vs. Monsters (Easy Version) Rating: 2500 Tags: brute force, implementation, math Solve time: 1m 15s Verified: no Solution Problem Understanding We are given a circle of n monsters, each with an initial energy level a_i . They are numbered from 1 to n , and each monster attacks its clockwise neighbor simultaneously in a single round. When a monster with energy x attacks a neighbor with...

Practice › Codeforces Solutions › Codeforces Round 935 (Div. 3) ›

CF 1945G - Cook and Porridge

CF 1945G - Cook and Porridge Rating: 2500 Tags: binary search, constructive algorithms, data structures, implementation Solve time: 1m 10s Verified: yes Solution Problem Understanding We are simulating a queue of students where the front of the queue is repeatedly served for a limited number of minutes. Each student, once served, leaves to “process” their porridge for a fixed number of minutes, and then returns to the queue. The return...

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Testing Round 11

Testing Round 11 Type: Special | Problems: 3 | Verified: 1/3 | Rating range: 1000-2300 | Time: 17m 39s Problem Name Rating Tags Solve Time Verified A Up the hill 1000 constructive-algorithms, implementation 5m 18s ✗ B New York Hotel 2100 greedy, math 11m 40s ✗ C Deciphering 2300 flows, graph-matchings 41s ✓

Practice › Codeforces Solutions › Codeforces Round 279 (Div. 2) ›

CF 490E - Restoring Increasing Sequence

CF 490E - Restoring Increasing Sequence Rating: 2000 Tags: binary search, brute force, greedy, implementation Solve time: 10m 45s Verified: no Solution Problem Understanding We are given a sequence of positive integers written on the board, but some of the digits have been replaced by question marks. Each question mark represents a lost digit, so our task is to restore the sequence to a strictly increasing list of positive integers....

Practice › Codeforces Solutions › Codeforces Round 946 (Div. 3) ›

CF 1974D - Ingenuity-2

CF 1974D - Ingenuity-2 Rating: 1400 Tags: constructive algorithms, greedy, implementation Solve time: 5m 16s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 937 (Div. 4) ›

CF 1950E - Nearly Shortest Repeating Substring

CF 1950E - Nearly Shortest Repeating Substring Rating: 1500 Tags: brute force, implementation, number theory, strings Solve time: 1m 22s Verified: yes Solution Problem Understanding We are given a string s of length n . We want to find the smallest possible length L such that there exists a pattern string k of length L , repeated exactly n / L times, producing a string c of length n ,...

Practice › Codeforces Solutions › Codeforces Round 937 (Div. 4) ›

CF 1950D - Product of Binary Decimals

CF 1950D - Product of Binary Decimals Rating: 1100 Tags: brute force, dp, implementation, number theory Solve time: 1m 17s Verified: yes Solution Problem Understanding We are given up to 50,000 independent queries. For each query, a number n is provided, where 1 ≤ n ≤ 100000 . A number is called a binary decimal if every digit in its usual decimal representation is either 0 or 1 . Examples...

Practice › Codeforces Solutions › Codeforces Round 940 (Div. 2) and CodeCraft-23 ›

CF 1957B - A BIT of a Construction

CF 1957B - A BIT of a Construction Rating: 1100 Tags: bitmasks, constructive algorithms, greedy, implementation Solve time: 3m 57s Verified: no Solution Problem Understanding We are asked to construct a sequence of n non-negative integers that sum to a given value k , while maximizing the number of distinct 1 bits in the binary representation of their bitwise OR. In other words, we are free to distribute k across...

Practice › Codeforces Solutions › Codeforces Round 282 (Div. 2) ›

CF 495A - Digital Counter

CF 495A - Digital Counter Rating: 1100 Tags: implementation Solve time: 1m 39s Verified: yes Solution Problem Understanding The elevator always displays a two-digit floor number from 00 to 99 . Each digit is drawn using a seven-segment display. A segment can be broken. When a segment is broken, it cannot light up even if it should. The key observation is that broken segments can only turn an intended lit...

Practice › Codeforces Solutions › Codeforces Round 281 (Div. 2) ›

CF 493B - Vasya and Wrestling

CF 493B - Vasya and Wrestling Rating: 1400 Tags: implementation Solve time: 10m 54s Verified: no Solution Problem Understanding We are given a chronological log of wrestling techniques. Each entry is an integer that describes both who performed the move and how many points it contributed. A positive value means the first wrestler performed a move worth that many points, while a negative value means the second wrestler performed a...

Practice › Codeforces Solutions › Codeforces Round 938 (Div. 3) ›

CF 1955C - Inhabitant of the Deep Sea

CF 1955C - Inhabitant of the Deep Sea Rating: 1300 Tags: greedy, implementation, math Solve time: 1m 10s Verified: no Solution Problem Understanding We are given a line of ships, each with some durability, and a fixed attack pattern that always targets the current leftmost surviving ship, then the current rightmost surviving ship, and repeats this alternation until a total of $k$ attacks have been made or all ships sink....

Practice › Codeforces Solutions › Codeforces Round 275 (Div. 2) ›

CF 483A - Counterexample

CF 483A - Counterexample Rating: 1100 Tags: brute force, implementation, math, number theory Solve time: 10m 52s Verified: no Solution Problem Understanding We are asked to construct three integers inside a given interval such that they form a very specific pattern of coprimality relationships. We need three distinct numbers $a < b < c$, all lying between $l$ and $r$, where adjacent pairs $(a,b)$ and $(b,c)$ share no common divisors...

Practice › Codeforces Solutions › CodeTON Round 8 (Div. 1 + Div. 2, Rated, Prizes!) ›

CF 1942D - Learning to Paint

CF 1942D - Learning to Paint Rating: 2100 Tags: binary search, data structures, dfs and similar, dp, greedy, implementation, sortings Solve time: 1m 30s Verified: no Solution Problem Understanding We are asked to help Elsie evaluate her paintings on a 1D canvas of n cells. Each cell can be painted or left empty, and the painting's beauty is determined by a 2D array a . Specifically, for every maximal contiguous...

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Educational Codeforces Round 166 (Rated for Div. 2)

Educational Codeforces Round 166 (Rated for Div. 2) Type: Div. 2 | Problems: 6 | Verified: 0/6 | Rating range: 800-2800 | Time: 31m 36s Problem Name Rating Tags Solve Time Verified A Verify Password 800 implementation, sortings, strings 5m 18s ✗ B Increase/Decrease/Copy 1100 greedy, implementation 5m 15s ✗ C Job Interview 1600 binary-search, dp, greedy 5m 16s ✗ D Invertible Bracket Sequences 2000 binary-search, combinatorics, data-structures 5m 14s...

Practice › Codeforces Solutions › Codeforces Round 276 (Div. 2) ›

CF 485A - Factory

CF 485A - Factory Rating: 1400 Tags: implementation, math, matrices Solve time: 5m 22s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 938 (Div. 3) ›

CF 1955B - Progressive Square

CF 1955B - Progressive Square Rating: 1000 Tags: constructive algorithms, data structures, implementation, sortings Solve time: 49s Verified: yes Solution Problem Understanding We are given an $n \times n$ grid that is fully determined by three values: the top-left cell, and two fixed increments that govern movement downwards and rightwards. Moving one step down always adds $c$, and moving one step right always adds $d$. Because of this, every cell...

Practice › Codeforces Solutions › Codeforces Round 938 (Div. 3) ›

CF 1955G - GCD on a grid

CF 1955G - GCD on a grid Rating: 1900 Tags: brute force, dfs and similar, dp, implementation, math, number theory Solve time: 1m 6s Verified: yes Solution Problem Understanding We are given a rectangular grid of integers. A move starts at the top-left cell and ends at the bottom-right cell, and at each step we can only go either one cell down or one cell right. Every such move sequence...

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Codeforces Round 940 (Div. 2) and CodeCraft-23

Codeforces Round 940 (Div. 2) and CodeCraft-23 Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 800-1100 | Time: 4m 40s Problem Name Rating Tags Solve Time Verified A Stickogon 800 constructive-algorithms, greedy 43s ✓ B A BIT of a Construction 1100 bitmasks, constructive-algorithms, greedy 3m 57s ✗

Practice › Codeforces Solutions › Codeforces Round 281 (Div. 2) ›

CF 493C - Vasya and Basketball

CF 493C - Vasya and Basketball Rating: 1600 Tags: binary search, brute force, data structures, implementation, sortings, two pointers Solve time: 54s Verified: yes Solution Problem Understanding Vasya wants to maximize the point advantage of his team in a basketball game by choosing a threshold distance, d , that separates 2-point throws from 3-point throws. Each team has a list of distances from which they made successful throws. A throw...

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Codeforces Round 938 (Div. 3)

Codeforces Round 938 (Div. 3) Type: Div. 3 | Problems: 8 | Verified: 5/8 | Rating range: 800-2300 | Time: 7m 51s Problem Name Rating Tags Solve Time Verified A Yogurt Sale 800 math 54s ✓ B Progressive Square 1000 constructive-algorithms, data-structures, implementation 49s ✓ C Inhabitant of the Deep Sea 1300 greedy, implementation, math 1m 10s ✗ D Inaccurate Subsequence Search 1400 data-structures, two-pointers 46s ✓ E Long Inversions...

Practice › Codeforces Solutions › European Championship 2024 - Online Mirror (Unrated, ICPC Rules, Teams Preferred) ›

CF 1949J - Amanda the Amoeba

CF 1949J - Amanda the Amoeba Rating: 2600 Tags: graphs, implementation, trees, two pointers Solve time: 1m 3s Verified: no Solution Problem Understanding We are asked to guide Amanda the Amoeba from an initial configuration to a target configuration on a rectangular grid. Each configuration marks Amanda's body with * , free pixels with . , and blocked pixels with X . Her body is connected and contains at least...

Practice › Codeforces Solutions › Codeforces Round 936 (Div. 2) ›

CF 1946C - Tree Cutting

CF 1946C - Tree Cutting Rating: 1600 Tags: binary search, dp, greedy, implementation, trees Solve time: 2m 50s Verified: yes Solution Problem Understanding We are given a tree with $n$ vertices, which is a connected graph without cycles. The task is to remove exactly $k$ edges from this tree and determine the largest integer $x$ such that each resulting connected component has at least $x$ vertices. In simpler terms, we...

Practice › Codeforces Solutions › Codeforces Round 939 (Div. 2) ›

CF 1956E2 - Nene vs. Monsters (Hard Version)

CF 1956E2 - Nene vs. Monsters (Hard Version) Rating: 2700 Tags: brute force, greedy, implementation, math Solve time: 1m 1s Verified: no Solution Problem Understanding We are given a circle of monsters, each with an energy level. The monsters attack their neighbor in a fixed clockwise order: monster 1 attacks monster 2, monster 2 attacks monster 3, and so on, with the last monster attacking the first. The attack reduces...

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Codeforces Round 936 (Div. 2)

Codeforces Round 936 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 1/5 | Rating range: 800-2500 | Time: 10m 41s Problem Name Rating Tags Solve Time Verified A Median of an Array 800 greedy, implementation, sortings 2m 44s ✗ B Maximum Sum 1100 dp, greedy, math 2m 45s ✗ C Tree Cutting 1600 binary-search, dp, greedy 2m 50s ✓ D Birthday Gift 1900 bitmasks, brute-force, constructive-algorithms 1m 7s...

Practice › Codeforces Solutions › Codeforces Round 939 (Div. 2) ›

CF 1956D - Nene and the Mex Operator

CF 1956D - Nene and the Mex Operator Rating: 2000 Tags: bitmasks, brute force, constructive algorithms, divide and conquer, dp, greedy, implementation, math Solve time: 1m 10s Verified: yes Solution Problem Understanding We are given a short array of length at most 18. The only allowed move is to pick a contiguous segment, compute the mex of that segment, and overwrite the entire segment with that mex value. This operation...

Practice › Codeforces Solutions › Testing Round 11 ›

CF 491A - Up the hill

CF 491A - Up the hill Rating: 1000 Tags: constructive algorithms, implementation Solve time: 5m 18s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 277.5 (Div. 2) ›

CF 489C - Given Length and Sum of Digits...

CF 489C - Given Length and Sum of Digits... Rating: 1400 Tags: dp, greedy, implementation Solve time: 10m 53s Verified: no Solution Problem Understanding We are asked to construct two numbers of a specified length, m , whose digits sum to a given value, s . The first number should be the smallest possible, the second the largest. Both numbers are expressed in base 10 and cannot have leading zeroes...

Practice › Codeforces Solutions › Educational Codeforces Round 166 (Rated for Div. 2) ›

CF 1976A - Verify Password

CF 1976A - Verify Password Rating: 800 Tags: implementation, sortings, strings Solve time: 5m 18s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 279 (Div. 2) ›

CF 490B - Queue

CF 490B - Queue Rating: 1500 Tags: dsu, implementation Solve time: 11m 48s Verified: no Solution Problem Understanding Each line of input describes one student. For that student we know two IDs: a is the student standing immediately in front of him. b is the student standing immediately behind him. If one of those neighbors does not exist, the value is 0 . The records are given in arbitrary order,...

Practice › Codeforces Solutions › Codeforces Round 937 (Div. 4) ›

CF 1950C - Clock Conversion

CF 1950C - Clock Conversion Rating: 800 Tags: implementation, math Solve time: 51s Verified: yes Solution Problem Understanding We are given times expressed in the 24-hour clock format, for example 00:00 for midnight, 13:45 for one forty-five in the afternoon, or 23:59 for one minute before midnight. Our task is to convert each time into the 12-hour clock format, which uses the familiar AM and PM labels. In this system,...

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Educational Codeforces Round 164 (Rated for Div. 2)

Educational Codeforces Round 164 (Rated for Div. 2) Type: Div. 2 | Problems: 6 | Verified: 2/6 | Rating range: 900-3100 | Time: 7m 33s Problem Name Rating Tags Solve Time Verified A Painting the Ribbon 900 constructive-algorithms, greedy, math 1m 3s ✓ B Make It Ugly 1200 implementation, math 1m 15s ✗ C Long Multiplication 1200 greedy, math, number-theory 1m 13s ✗ D Colored Balls 1800 combinatorics, dp, math...

Practice › Codeforces Solutions › Codeforces Round 942 (Div. 1) ›

CF 1967F - Next and Prev

CF 1967F - Next and Prev Rating: 3200 Tags: brute force, data structures, implementation Solve time: 1m 20s Verified: no Solution Problem Understanding We are given a permutation, and we observe it evolving over time by revealing its prefix. After revealing the first $q$ elements, we throw away all values greater than $q$, but keep the relative order of the remaining values. This produces a reduced sequence that is again...

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Codeforces Round 946 (Div. 3)

Codeforces Round 946 (Div. 3) Type: Div. 3 | Problems: 7 | Verified: 0/7 | Rating range: 800-2000 | Time: 36m 53s Problem Name Rating Tags Solve Time Verified A Phone Desktop 800 greedy, math 5m 17s ✗ B Symmetric Encoding 800 implementation, sortings, strings 5m 18s ✗ C Beautiful Triple Pairs 1400 combinatorics, data-structures 5m 16s ✗ D Ingenuity-2 1400 constructive-algorithms, greedy, implementation 5m 16s ✗ E Money Buys...

Practice › Codeforces Solutions › Codeforces Round 946 (Div. 3) ›

CF 1974F - Cutting Game

CF 1974F - Cutting Game Rating: 1900 Tags: binary search, brute force, data structures, implementation, sortings, two pointers Solve time: 5m 16s Verified: no Solution

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Codeforces Round 947 (Div. 1 + Div. 2)

Codeforces Round 947 (Div. 1 + Div. 2) Type: Div. 1+2 | Problems: 9 | Verified: 0/9 | Rating range: 800-3500 | Time: 47m 41s Problem Name Rating Tags Solve Time Verified A Bazoka and Mocha's Array 800 brute-force, greedy, implementation 5m 18s ✗ B 378QAQ and Mocha's Array 1000 brute-force, greedy, math 5m 18s ✗ C Chamo and Mocha's Array 1200 binary-search, brute-force, greedy 5m 19s ✗ D Paint...

Practice › Codeforces Solutions › Codeforces Round 937 (Div. 4) ›

CF 1950A - Stair, Peak, or Neither?

CF 1950A - Stair, Peak, or Neither? Rating: 800 Tags: implementation Solve time: 1m 4s Verified: yes Solution Problem Understanding We are given three digits, a , b , and c , and must classify their relationship. A sequence is called a stair when the values strictly increase from left to right, meaning a < b < c . A sequence is called a peak when the middle value is...

Practice › Codeforces Solutions › Codeforces Round 942 (Div. 1) ›

CF 1967A - Permutation Counting

CF 1967A - Permutation Counting Rating: 1400 Tags: binary search, greedy, implementation, math, sortings Solve time: 1m 16s Verified: no Solution Problem Understanding We are given a set of cards, each labeled with a number from 1 to n. For each number i, we have a_i cards of that type. We also have k coins, and each coin allows us to buy a new card of any type, so we...

Practice › Codeforces Solutions › Codeforces Round 937 (Div. 4) ›

CF 1950F - 0, 1, 2, Tree!

CF 1950F - 0, 1, 2, Tree! Rating: 1700 Tags: bitmasks, brute force, greedy, implementation, trees Solve time: 1m Verified: no Solution Problem Understanding We are asked to construct a rooted tree with a specific number of vertices having 0, 1, or 2 children. The input gives three numbers: a vertices with 2 children, b vertices with 1 child, and c vertices that are leaves. The task is to determine...

Practice › Codeforces Solutions › Codeforces Round 938 (Div. 3) ›

CF 1955E - Long Inversions

CF 1955E - Long Inversions Rating: 1700 Tags: brute force, greedy, implementation, sortings Solve time: 51s Verified: yes Solution Problem Understanding We are given a binary string and an operation that flips a block of fixed length $k$, turning every 0 into 1 and every 1 into 0. We may apply this operation as many times as we want, but the chosen length $k$ is fixed for the entire process....

Practice › Codeforces Solutions › Educational Codeforces Round 166 (Rated for Div. 2) ›

CF 1976B - Increase/Decrease/Copy

CF 1976B - Increase/Decrease/Copy Rating: 1100 Tags: greedy, implementation Solve time: 5m 15s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 937 (Div. 4) ›

CF 1950B - Upscaling

CF 1950B - Upscaling Rating: 800 Tags: implementation Solve time: 45s Verified: yes Solution Problem Understanding We are asked to generate a checkerboard pattern that is made of larger $2 \times 2$ tiles. Each tile is either fully filled with the character # or fully filled with . . The size of the grid is determined by an input integer $n$, and the final grid has dimensions $2n \times 2n...

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Codeforces Round 276 (Div. 2)

Codeforces Round 276 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 0/2 | Rating range: 1300-1400 | Time: 16m 31s Problem Name Rating Tags Solve Time Verified A Factory 1400 implementation, math, matrices 5m 22s ✗ B Valuable Resources 1300 brute-force, greedy 11m 9s ✗

Practice › Codeforces Solutions › Codeforces Round 947 (Div. 1 + Div. 2) ›

CF 1975E - Chain Queries

CF 1975E - Chain Queries Rating: 2100 Tags: binary search, data structures, dfs and similar, implementation, trees Solve time: 5m 17s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 942 (Div. 1) ›

CF 1967D - Long Way to be Non-decreasing

CF 1967D - Long Way to be Non-decreasing Rating: 2800 Tags: binary search, dfs and similar, graphs, implementation, shortest paths, two pointers Solve time: 1m 43s Verified: yes Solution Problem Understanding We are given an array where each position contains a value in the range $1$ to $m$, and a second array that defines a deterministic transformation on values: every value $x$ has a fixed replacement $b_x$. One operation, called...

Practice › Codeforces Solutions › Codeforces Round 936 (Div. 2) ›

CF 1946D - Birthday Gift

CF 1946D - Birthday Gift Rating: 1900 Tags: bitmasks, brute force, constructive algorithms, greedy, implementation Solve time: 1m 7s Verified: no Solution Problem Understanding We are given an array and we are allowed to split it into a sequence of contiguous segments. Each segment is evaluated by taking the bitwise XOR of its elements. Once all segment XORs are computed, we combine those results using bitwise OR, left to right...

Practice › Codeforces Solutions › Codeforces Round 947 (Div. 1 + Div. 2) ›

CF 1975A - Bazoka and Mocha's Array

CF 1975A - Bazoka and Mocha's Array Rating: 800 Tags: brute force, greedy, implementation, sortings Solve time: 5m 18s Verified: no Solution

Practice › Codeforces Solutions › CodeTON Round 8 (Div. 1 + Div. 2, Rated, Prizes!) ›

CF 1942F - Farmer John's Favorite Function

CF 1942F - Farmer John's Favorite Function Rating: 2700 Tags: brute force, data structures, implementation, math Solve time: 2m 10s Verified: yes Solution Problem Understanding We have an array $a$, and a recursively defined value: $$f(1)=\sqrt{a_1}, \qquad f(i)=\sqrt{f(i-1)+a_i}.$$ After every point update $a_k \leftarrow x$, we need the integer part of $f(n)$. The first obstacle is that the recurrence uses real numbers. A direct simulation would repeatedly evaluate square roots...

Practice › Codeforces Solutions › Codeforces Round 945 (Div. 2) ›

CF 1973A - Chess For Three

CF 1973A - Chess For Three Rating: 900 Tags: brute force, dp, implementation, math Solve time: 5m 14s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 934 (Div. 1) ›

CF 1943B - Non-Palindromic Substring

CF 1943B - Non-Palindromic Substring Rating: 2000 Tags: hashing, implementation, math, strings Solve time: 1m 20s Verified: no Solution Problem Understanding We are given a string and multiple queries, each asking for a contiguous substring of the original string. For each query, we need to calculate a value f(t) for that substring t . The function f(t) is the sum of all lengths k such that there exists at least...

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Codeforces Round 280 (Div. 2)

Codeforces Round 280 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 1/3 | Rating range: 1400-2000 | Time: 17m 42s Problem Name Rating Tags Solve Time Verified C Vanya and Exams 1400 greedy, sortings 57s ✓ D Vanya and Computer Game 1800 binary-search, implementation, math 11m 25s ✗ E Vanya and Field 2000 math 5m 20s ✗

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Codeforces Round 278 (Div. 1)

Codeforces Round 278 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 0/4 | Rating range: 1800-3200 | Time: 27m 2s Problem Name Rating Tags Solve Time Verified A Fight the Monster 1800 binary-search, brute-force, implementation 5m 21s ✗ C Prefix Product Sequence 2300 constructive-algorithms, math, number-theory 5m 22s ✗ D Conveyor Belts 2700 data-structures 5m 24s ✗ E Tourists 3200 data-structures, dfs-and-similar, graphs 10m 55s ✗

Practice › Codeforces Solutions › Codeforces Round 277 (Div. 2) ›

CF 486A - Calculating Function

CF 486A - Calculating Function Rating: 800 Tags: implementation, math Solve time: 10m 49s Verified: no Solution Problem Understanding We are given a single positive integer and asked to evaluate a function built by alternating addition and subtraction of consecutive integers starting from 1. The sequence begins by subtracting 1, then adding 2, subtracting 3, adding 4, and so on until we reach n. The sign of each term depends...

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Codeforces Round 934 (Div. 1)

Codeforces Round 934 (Div. 1) Type: Div. 1 | Problems: 8 | Verified: 1/8 | Rating range: 1300-3500 | Time: 10m 17s Problem Name Rating Tags Solve Time Verified A MEX Game 1 1300 games, greedy 1m 9s ✓ B Non-Palindromic Substring 2000 hashing, implementation, math 1m 20s ✗ C Tree Compass 2300 constructive-algorithms, dfs-and-similar, greedy 1m 16s ✗ D1 Counting Is Fun (Easy Version) 2400 brute-force, combinatorics, dp 1m...

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Codeforces Round 277 (Div. 2)

Codeforces Round 277 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 0/4 | Rating range: 800-2200 | Time: 26m 47s Problem Name Rating Tags Solve Time Verified A Calculating Function 800 implementation, math 10m 49s ✗ B OR in Matrix 1300 greedy, hashing, implementation 5m 23s ✗ D Valid Sets 2100 dfs-and-similar, dp, math 5m 18s ✗ E LIS of Sequence 2200 data-structures, dp, greedy 5m 17s ✗

Practice › Codeforces Solutions › April Fools Day Contest 2024 ›

CF 1952H - Palindrome

CF 1952H - Palindrome Rating: - Tags: *special, implementation, strings Solve time: 1m 12s Verified: no Solution Problem Understanding The task is to determine, for each given string, whether it reads the same forwards and backwards. A palindrome is such a string, like "radar" or "racecar", while a string like "ac" is not. The input consists of multiple test cases, each providing a string of up to 100 lowercase English...

Practice › Codeforces Solutions › Codeforces Round 941 (Div. 2) ›

CF 1966B - Rectangle Filling

CF 1966B - Rectangle Filling Rating: 1100 Tags: constructive algorithms, implementation Solve time: 1m 8s Verified: no Solution Problem Understanding We are given a grid of size $n \times m$ composed of white and black squares. The task is to determine whether it is possible to make all squares in the grid the same color using a specific operation any number of times. The operation allows selecting two squares of...

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Codeforces Round 937 (Div. 4)

Codeforces Round 937 (Div. 4) Type: Div. 4 | Problems: 7 | Verified: 6/7 | Rating range: 800-1900 | Time: 7m 41s Problem Name Rating Tags Solve Time Verified A Stair, Peak, or Neither? 800 implementation 1m 4s ✓ B Upscaling 800 implementation 45s ✓ C Clock Conversion 800 implementation, math 51s ✓ D Product of Binary Decimals 1100 brute-force, dp, implementation 1m 17s ✓ E Nearly Shortest Repeating Substring...

Practice › Codeforces Solutions › Codeforces Round 937 (Div. 4) ›

CF 1950G - Shuffling Songs

CF 1950G - Shuffling Songs Rating: 1900 Tags: bitmasks, dfs and similar, dp, graphs, hashing, implementation, strings Solve time: 1m 22s Verified: yes Solution Problem Understanding Each song has two attributes, a genre and a writer. After removing some songs, we are allowed to reorder the remaining songs arbitrarily. The goal is to arrange them so that every pair of neighboring songs shares at least one attribute: either the same...

Practice › Codeforces Solutions › Codeforces Round 277.5 (Div. 2) ›

CF 489A - SwapSort

CF 489A - SwapSort Rating: 1200 Tags: greedy, implementation, sortings Solve time: 11m 31s Verified: no Solution Problem Understanding We are given an array of integers and must transform it into non-decreasing order using swaps. The output is not the sorted array itself. Instead, we must print a sequence of index pairs, where each pair represents a swap performed on the array. The unusual part of the task is that...

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Codeforces Round 281 (Div. 2)

Codeforces Round 281 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 1300-2800 | Time: 16m 6s Problem Name Rating Tags Solve Time Verified A Vasya and Football 1300 implementation 1m 38s ✓ B Vasya and Wrestling 1400 implementation 10m 54s ✗ C Vasya and Basketball 1600 binary-search, brute-force, data-structures 54s ✓ D Vasya and Chess 1700 constructive-algorithms, games, math 1m 25s ✓ E Vasya...

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Codeforces Round 945 (Div. 2)

Codeforces Round 945 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 0/6 | Rating range: 900-3100 | Time: 31m 30s Problem Name Rating Tags Solve Time Verified A Chess For Three 900 brute-force, dp, implementation 5m 14s ✗ B Cat, Fox and the Lonely Array 1300 binary-search, bitmasks, data-structures 5m 16s ✗ C Cat, Fox and Double Maximum 1700 constructive-algorithms, greedy, implementation 5m 15s ✗ D Cat, Fox...

Practice › Codeforces Solutions › Codeforces Round 936 (Div. 2) ›

CF 1946A - Median of an Array

CF 1946A - Median of an Array Rating: 800 Tags: greedy, implementation, sortings Solve time: 2m 44s Verified: no Solution Problem Understanding We are given an array of integers, and our task is to increase its median by performing a series of operations. Each operation consists of picking a single element and incrementing it by one. The median of an array is defined as the middle element in the sorted...

Practice › Codeforces Solutions › Educational Codeforces Round 163 (Rated for Div. 2) ›

CF 1948E - Clique Partition

CF 1948E - Clique Partition Rating: 2100 Tags: brute force, constructive algorithms, graphs, greedy, implementation Solve time: 2m 41s Verified: no Solution Problem Understanding We are given a problem where we need to assign integers to vertices of an initially empty graph and then construct edges based on a Manhattan-like distance metric. Specifically, for vertices labeled $1$ through $n$, each vertex receives a distinct integer from $1$ to $n$. After...

Practice › Codeforces Solutions › Codeforces Round 277 (Div. 2) ›

CF 486B - OR in Matrix

CF 486B - OR in Matrix Rating: 1300 Tags: greedy, hashing, implementation Solve time: 5m 23s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 280 (Div. 2) ›

CF 492D - Vanya and Computer Game

CF 492D - Vanya and Computer Game Rating: 1800 Tags: binary search, implementation, math, sortings Solve time: 11m 25s Verified: no Solution Problem Understanding The game produces an infinite sequence of hits. Vanya attacks every $\frac{1}{x}$ seconds, so his hits happen at times $$\frac1x,\frac2x,\frac3x,\dots$$ Vova attacks every $\frac{1}{y}$ seconds, so his hits happen at times $$\frac1y,\frac2y,\frac3y,\dots$$ Whenever a hit occurs, it contributes one damage point. If both players hit at...

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Codeforces Round 277.5 (Div. 2)

Codeforces Round 277.5 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 0/4 | Rating range: 1200-2300 | Time: 38m 30s Problem Name Rating Tags Solve Time Verified A SwapSort 1200 greedy, implementation, sortings 11m 31s ✗ C Given Length and Sum of Digits... 1400 dp, greedy, implementation 10m 53s ✗ E Hiking 2300 binary-search, dp 5m 18s ✗ F Special Matrices 2100 combinatorics, dp 10m 48s ✗

Practice › Codeforces Solutions › Codeforces Round 260 (Div. 1) ›

CF 455B - A Lot of Games

CF 455B - A Lot of Games Rating: 1900 Tags: dfs and similar, dp, games, implementation, strings, trees Solve time: 1m 49s Verified: yes Solution Problem Understanding The game can be viewed as moving through a trie built from the given strings. We start at the root, which represents the empty string. On each turn a player chooses one outgoing edge, corresponding to appending a character. The current string must...

Practice › Codeforces Solutions › Codeforces Round 261 (Div. 2) ›

CF 459A - Pashmak and Garden

CF 459A - Pashmak and Garden Rating: 1200 Tags: implementation Solve time: 1m 3s Verified: yes Solution Problem Understanding We are given the coordinates of two distinct trees on a Cartesian plane, and we know that the garden forms a perfect square aligned with the axes. Each vertex of the square has a tree, so there are exactly four trees. The task is to determine the coordinates of the other...

Practice › Codeforces Solutions › Codeforces Round 262 (Div. 2) ›

CF 460A - Vasya and Socks

CF 460A - Vasya and Socks Rating: 900 Tags: brute force, implementation, math Solve time: 1m 32s Verified: yes Solution Problem Understanding Vasya starts with a certain number of sock pairs. Every morning he uses exactly one pair, and that pair is gone forever at the end of the day. There is one special event: after every day whose number is a multiple of m , his mother buys him...

Practice › Codeforces Solutions › Codeforces Round 267 (Div. 2) ›

CF 467C - George and Job

CF 467C - George and Job Rating: 1700 Tags: dp, implementation Solve time: 1m 35s Verified: no Solution Problem Understanding George wants to maximize his earnings by choosing segments of work from a list of tasks, each with a given profit. The tasks are arranged sequentially in an array p of length n . He must select exactly k non-overlapping segments, each of length m . A segment is defined...

Practice › Codeforces Solutions › Codeforces Round 274 (Div. 2) ›

CF 479B - Towers

CF 479B - Towers Rating: 1400 Tags: brute force, constructive algorithms, greedy, implementation, sortings Solve time: 1m 3s Verified: yes Solution Problem Understanding We are given several stacks of unit cubes, each stack having an initial height. In a single move, we can take exactly one cube from the top of one stack and place it on top of another stack. Over time, this allows us to redistribute cubes between...

Practice › Codeforces Solutions › MemSQL Start[c]UP 2.0 - Round 1 ›

CF 452A - Eevee

CF 452A - Eevee Rating: 1000 Tags: brute force, implementation, strings Solve time: 1m 6s Verified: yes Solution Problem Understanding We are given a partially filled crossword slot and asked to identify which of Eevee's evolutions fits it. The input specifies the length of the word and a string pattern using lowercase letters and dots, where a dot represents an unknown character. Our task is to find which Pokémon name...

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Codeforces Round 271 (Div. 2)

Codeforces Round 271 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 6/6 | Rating range: 900-2100 | Time: 9m 19s Problem Name Rating Tags Solve Time Verified A Keyboard 900 implementation 1m 4s ✓ B Worms 1200 binary-search, implementation 1m 36s ✓ C Captain Marmot 2000 brute-force, geometry 1m 12s ✓ D Flowers 1700 dp 1m 50s ✓ E Pillars 2000 binary-search, data-structures, dp 2m 1s ✓ F...

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Codeforces Round 272 (Div. 2)

Codeforces Round 272 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1000-2200 | Time: 12m 19s Problem Name Rating Tags Solve Time Verified A Dreamoon and Stairs 1000 implementation, math 1m 32s ✓ B Dreamoon and WiFi 1300 bitmasks, brute-force, combinatorics 1m 35s ✓ C Dreamoon and Sums 1600 math 1m 19s ✓ D Dreamoon and Sets 1900 constructive-algorithms, greedy, math 2m 8s ✓...

Practice › Codeforces Solutions › Codeforces Round 259 (Div. 2) ›

CF 454A - Little Pony and Crystal Mine

CF 454A - Little Pony and Crystal Mine Rating: 800 Tags: implementation Solve time: 1m 27s Verified: yes Solution Problem Understanding We need to print an odd-sized square grid that contains a diamond shape. Every cell belonging to the diamond is represented by the character D , and every other cell is represented by * . The input contains a single odd integer n . The output must consist of...

Practice › Codeforces Solutions › Codeforces Round 265 (Div. 2) ›

CF 465B - Inbox (100500)

CF 465B - Inbox (100500) Rating: 1000 Tags: implementation Solve time: 5m 22s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 264 (Div. 2) ›

CF 463A - Caisa and Sugar

CF 463A - Caisa and Sugar Rating: 1200 Tags: brute force, implementation Solve time: 1m Verified: yes Solution Problem Understanding We are given a fixed amount of money expressed in dollars, and a list of sugar options in a supermarket. Each option has a price written as dollars and cents. Caisa can choose exactly one type of sugar, pay for it using his available money, and receive change if he...

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Codeforces Round 265 (Div. 2)

Codeforces Round 265 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 0/2 | Rating range: 900-1000 | Time: 10m 43s Problem Name Rating Tags Solve Time Verified A inc ARG 900 implementation 5m 21s ✗ B Inbox (100500) 1000 implementation 5m 22s ✗

Practice › Codeforces Solutions › Surprise Language Round 7 ›

CF 470A - Crystal Ball Sequence

CF 470A - Crystal Ball Sequence Rating: 1400 Tags: *special, implementation Solve time: 1m 36s Verified: yes Solution Problem Understanding The sequence in this problem comes from counting lattice points inside a growing hexagon on a hexagonal grid. Instead of having to construct the hexagon or count points manually, the problem already gives the formula for the sequence: $$H_n = 3 \cdot n \cdot (n+1) + 1$$ The input consists...

Practice › Codeforces Solutions › Codeforces Round 272 (Div. 2) ›

CF 476A - Dreamoon and Stairs

CF 476A - Dreamoon and Stairs Rating: 1000 Tags: implementation, math Solve time: 1m 32s Verified: yes Solution Problem Understanding Dreamoon wants to reach the top of a staircase containing n steps. Every move can cover either 1 step or 2 steps. Among all possible ways to reach exactly step n , we need the number of moves used to be divisible by m . The task is not asking...

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Codeforces Round 268 (Div. 2)

Codeforces Round 268 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1300 | Time: 2m 52s Problem Name Rating Tags Solve Time Verified A I Wanna Be the Guy 800 greedy, implementation 1m 38s ✓ B Chat Online 1300 implementation 1m 14s ✓

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CF 472E - Design Tutorial: Learn from a Game

CF 472E - Design Tutorial: Learn from a Game Rating: 2800 Tags: constructive algorithms, implementation Solve time: 3m 25s Verified: no Solution Problem Understanding We have two boards of the same size. A move starts by choosing one cell and placing a finger on it. After that, the finger walks through adjacent cells. Every time the finger moves from one cell to another, the two orbs in those cells are...

Practice › Codeforces Solutions › Codeforces Round 267 (Div. 2) ›

CF 467B - Fedor and New Game

CF 467B - Fedor and New Game Rating: 1100 Tags: bitmasks, brute force, constructive algorithms, implementation Solve time: 1m 19s Verified: yes Solution Problem Understanding We are given a game with several players, each controlling an army composed of different types of soldiers. Each army is represented as a non-negative integer where the binary representation encodes the presence of soldier types: a bit set to 1 means the army includes...

Practice › Codeforces Solutions › Codeforces Round 263 (Div. 2) ›

CF 462A - Appleman and Easy Task

CF 462A - Appleman and Easy Task Rating: 1000 Tags: brute force, implementation Solve time: 1m 2s Verified: yes Solution Problem Understanding We are given an n × n board, where each cell contains either an 'x' or an 'o'. The task is to check a local property for every cell: whether the number of orthogonally adjacent cells containing 'o' is even. Two cells are adjacent if they share a...

Practice › Codeforces Solutions › Codeforces Round 259 (Div. 2) ›

CF 454B - Little Pony and Sort by Shift

CF 454B - Little Pony and Sort by Shift Rating: 1200 Tags: implementation Solve time: 1m 7s Verified: yes Solution Problem Understanding We are given a sequence of integers arranged in a line, and our goal is to sort them in non-decreasing order by repeatedly performing a single allowed operation: moving the last element of the sequence to the front. Conceptually, we are allowed to "rotate" the array right by...

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Codeforces Round 273 (Div. 2)

Codeforces Round 273 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1100-2900 | Time: 6m Problem Name Rating Tags Solve Time Verified A Initial Bet 1100 implementation 59s ✓ B Random Teams 1300 combinatorics, constructive-algorithms, greedy 1m 12s ✓ C Table Decorations 1800 greedy 1m 9s ✓ D Red-Green Towers 2000 dp 1m 3s ✓ E Wavy numbers 2900 brute-force, dfs-and-similar, meet-in-the-middle 1m 37s...

Practice › Codeforces Solutions › Codeforces Round 264 (Div. 2) ›

CF 463C - Gargari and Bishops

CF 463C - Gargari and Bishops Rating: 1900 Tags: greedy, hashing, implementation Solve time: 1m 6s Verified: yes Solution Problem Understanding We have an $n \times n$ chessboard, and each cell has a non-negative integer representing money. The goal is to place exactly two bishops such that no cell is attacked by both bishops, and we maximize the total money collected from all cells that are attacked by at least...

Practice › Codeforces Solutions › Codeforces Round 267 (Div. 2) ›

CF 467A - George and Accommodation

CF 467A - George and Accommodation Rating: 800 Tags: implementation Solve time: 1m 1s Verified: yes Solution Problem Understanding The problem presents a simple scenario: George and Alex want to find a dormitory room together. Each room in the dormitory has a current occupancy and a maximum capacity. The input gives the number of rooms and, for each room, the current number of occupants and the total capacity. The task...

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Surprise Language Round 7

Surprise Language Round 7 Type: Special | Problems: 8 | Verified: 8/8 | Rating range: 1400-2300 | Time: 10m 9s Problem Name Rating Tags Solve Time Verified A Crystal Ball Sequence 1400 *special, implementation 1m 36s ✓ B Hexakosioihexekontahexaphobia 1800 *special 1m 6s ✓ C Eval 1900 *special 1m 2s ✓ D Caesar Cipher 1900 *special 1m 24s ✓ E Chessboard 1900 *special 1m 29s ✓ F Pairwise Sums 2300...

Practice › Codeforces Solutions › Codeforces Round 273 (Div. 2) ›

CF 478A - Initial Bet

CF 478A - Initial Bet Rating: 1100 Tags: implementation Solve time: 59s Verified: yes Solution Problem Understanding We are given the final state of a system with five participants who started a game under a very rigid rule: everyone begins with the same unknown positive number of coins, call it $b$. After this initialization, coins are only moved between players. No coins are created or destroyed during the process; every...

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MemSQL Start[c]UP 2.0 - Round 1

MemSQL Start[c]UP 2.0 - Round 1 Type: Special | Problems: 5 | Verified: 4/5 | Rating range: 1000-2700 | Time: 9m 36s Problem Name Rating Tags Solve Time Verified A Eevee 1000 brute-force, implementation, strings 1m 6s ✓ B 4-point polyline 1800 brute-force, constructive-algorithms, geometry 2m 2s ✓ C Magic Trick 2100 combinatorics, math, probabilities 1m 44s ✓ E Three strings 2400 data-structures, dsu, string-suffix-structures 2m 7s ✓ F Permutation...

Practice › Codeforces Solutions › Bayan 2015 Contest Warm Up ›

CF 475B - Strongly Connected City

CF 475B - Strongly Connected City Rating: 1400 Tags: brute force, dfs and similar, graphs, implementation Solve time: 59s Verified: yes Solution Problem Understanding We are asked to determine if a city with a grid of horizontal and vertical streets is "strongly connected" once each street is made one-way. The city can be visualized as a grid of intersections, with n horizontal streets and m vertical streets forming n ×...

Practice › Codeforces Solutions › Codeforces Round 261 (Div. 2) ›

CF 459B - Pashmak and Flowers

CF 459B - Pashmak and Flowers Rating: 1300 Tags: combinatorics, implementation, sortings Solve time: 1m 31s Verified: yes Solution Problem Understanding We are given the beauty values of n flowers. We must choose exactly two flowers. Among all possible pairs, we are interested only in pairs whose beauty difference is as large as possible. The task is to output two values: First, the maximum possible difference between the beauties of...

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Codeforces Round 269 (Div. 2)

Codeforces Round 269 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 1100-2700 | Time: 8m 43s Problem Name Rating Tags Solve Time Verified A MUH and Sticks 1100 implementation 1m 21s ✓ B MUH and Important Things 1300 implementation, sortings 1m 41s ✗ C MUH and House of Cards 1700 binary-search, brute-force, greedy 1m 42s ✓ D MUH and Cube Walls 1800 string-suffix-structures, strings...

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Codeforces Round 274 (Div. 2)

Codeforces Round 274 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 1000-1900 | Time: 19m 33s Problem Name Rating Tags Solve Time Verified A Expression 1000 brute-force, math 5m 21s ✗ B Towers 1400 brute-force, constructive-algorithms, greedy 1m 3s ✓ C Exams 1400 greedy, sortings 10m 58s ✗ D Long Jumps 1700 binary-search, greedy, implementation 1m 9s ✓ E Riding in a Lift 1900...

Practice › Codeforces Solutions › Bayan 2015 Contest Warm Up ›

CF 475A - Bayan Bus

CF 475A - Bayan Bus Rating: 1100 Tags: implementation Solve time: 1m 59s Verified: yes Solution Problem Understanding The bus layout is fixed and already drawn for us. There are 34 passenger seats in total. Passengers always occupy seats in a very specific order: they start from the last row, fill it from left to right, then move upward row by row. Whenever several seats are available in the current...

Practice › Codeforces Solutions › Codeforces Round 258 (Div. 2) ›

CF 451A - Game With Sticks

CF 451A - Game With Sticks Rating: 900 Tags: implementation Solve time: 1m 19s Verified: yes Solution Problem Understanding The game is played on a grid formed by n horizontal sticks and m vertical sticks. Every horizontal stick intersects every vertical stick, creating n * m intersection points. On a turn, a player chooses one remaining intersection point. Choosing that point removes the horizontal stick and the vertical stick passing...

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Codeforces Round 267 (Div. 2)

Codeforces Round 267 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 800-2400 | Time: 6m 31s Problem Name Rating Tags Solve Time Verified A George and Accommodation 800 implementation 1m 1s ✓ B Fedor and New Game 1100 bitmasks, brute-force, constructive-algorithms 1m 19s ✓ C George and Job 1700 dp, implementation 1m 35s ✗ D Fedor and Essay 2400 dfs-and-similar, dp, graphs 1m 26s...

Practice › Codeforces Solutions › Codeforces Round 269 (Div. 2) ›

CF 471A - MUH and Sticks

CF 471A - MUH and Sticks Rating: 1100 Tags: implementation Solve time: 1m 21s Verified: yes Solution Problem Understanding We are given exactly six stick lengths. To build an animal, four of the sticks must be used as legs, which means those four sticks must all have the same length. After choosing the four leg sticks, two sticks remain. These determine the animal type. For an elephant, the remaining two...

Practice › Codeforces Solutions ›

Codeforces Round 260 (Div. 1)

Codeforces Round 260 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1500-2900 | Time: 7m 50s Problem Name Rating Tags Solve Time Verified A Boredom 1500 dp 1m 31s ✓ B A Lot of Games 1900 dfs-and-similar, dp, games 1m 49s ✓ C Civilization 2100 dfs-and-similar, dp, dsu 2m 1s ✓ D Serega and Fun 2700 data-structures 1m 27s ✓ E Function 2900 data-structures...

Practice › Codeforces Solutions › Codeforces Round 257 (Div. 2) ›

CF 450A - Jzzhu and Children

CF 450A - Jzzhu and Children Rating: 1000 Tags: implementation Solve time: 1m 34s Verified: yes Solution Problem Understanding We have a line of children. Child i wants a[i] candies in total. Every time a child reaches the front of the line, they receive exactly m candies. If the child has still not received enough candies after that distribution, they move to the back of the line. Otherwise, they leave...

Practice › Codeforces Solutions › Codeforces Round 264 (Div. 2) ›

CF 463B - Caisa and Pylons

CF 463B - Caisa and Pylons Rating: 1100 Tags: brute force, implementation, math Solve time: 59s Verified: yes Solution Problem Understanding We are given a sequence of pylons arranged in a line, starting from position 0 up to position n. The first pylon is fixed at height 0, and every other pylon has a given height. A player starts at pylon 0 with zero energy and moves strictly forward, one...

Practice › Codeforces Solutions ›

Codeforces Round 266 (Div. 2)

Codeforces Round 266 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 1200-2100 | Time: 6m 29s Problem Name Rating Tags Solve Time Verified A Cheap Travel 1200 implementation 54s ✓ B Wonder Room 2000 brute-force, math 1m 22s ✓ C Number of Ways 1700 binary-search, brute-force, data-structures 1m 18s ✓ D Increase Sequence 2100 combinatorics, dp 1m 14s ✗ E Information Graph 2100 dfs-and-similar,...

Practice › Codeforces Solutions › Codeforces Round 265 (Div. 2) ›

CF 465A - inc ARG

CF 465A - inc ARG Rating: 900 Tags: implementation Solve time: 5m 21s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 269 (Div. 2) ›

CF 471B - MUH and Important Things

CF 471B - MUH and Important Things Rating: 1300 Tags: implementation, sortings Solve time: 1m 41s Verified: no Solution Problem Understanding We are given a list of tasks, each with an associated difficulty level, and we need to produce three different sequences in which all tasks are completed. Each sequence must respect the rule that tasks can only be reordered if their difficulties are equal. In other words, for any...

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Codeforces Round 259 (Div. 2)

Codeforces Round 259 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1200 | Time: 2m 34s Problem Name Rating Tags Solve Time Verified A Little Pony and Crystal Mine 800 implementation 1m 27s ✓ B Little Pony and Sort by Shift 1200 implementation 1m 7s ✓

Practice › Codeforces Solutions ›

Codeforces Round 262 (Div. 2)

Codeforces Round 262 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 900-2700 | Time: 6m 14s Problem Name Rating Tags Solve Time Verified A Vasya and Socks 900 brute-force, implementation, math 1m 32s ✓ B Little Dima and Equation 1500 brute-force, implementation, math 1m 6s ✓ C Present 1700 binary-search, data-structures, greedy 1m ✓ D Little Victor and Set 2300 brute-force, constructive-algorithms, math 1m...

Practice › Codeforces Solutions ›

Codeforces Round 261 (Div. 2)

Codeforces Round 261 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1200-1900 | Time: 8m 37s Problem Name Rating Tags Solve Time Verified A Pashmak and Garden 1200 implementation 1m 3s ✓ B Pashmak and Flowers 1300 combinatorics, implementation, sortings 1m 31s ✓ C Pashmak and Buses 1900 combinatorics, constructive-algorithms, math 1m 59s ✗ D Pashmak and Parmida's problem 1800 data-structures, divide-and-conquer, sortings 2m...

Practice › Codeforces Solutions › Codeforces Round 258 (Div. 2) ›

CF 451C - Predict Outcome of the Game

CF 451C - Predict Outcome of the Game Rating: 1700 Tags: brute force, implementation, math Solve time: 1m 55s Verified: yes Solution Problem Understanding We have a football tournament involving three teams. Every game produces exactly one winner, so each played game contributes exactly one win to one of the teams. After k games have already been played, we do not know the exact number of wins of the three...

Practice › Codeforces Solutions › Codeforces Round 274 (Div. 2) ›

CF 479D - Long Jumps

CF 479D - Long Jumps Rating: 1700 Tags: binary search, greedy, implementation Solve time: 1m 9s Verified: yes Solution Problem Understanding We are given a sorted set of marks on a number line from 0 to a length l , where each mark is an integer position. Some marks already exist, including the endpoints 0 and l . Using these marks, we can measure any distance that equals the difference...

Practice › Codeforces Solutions › Codeforces Round 271 (Div. 2) ›

CF 474A - Keyboard

CF 474A - Keyboard Rating: 900 Tags: implementation Solve time: 1m 4s Verified: yes Solution Problem Understanding The problem presents a keyboard with three rows of characters arranged exactly like a standard QWERTY layout. Mole is typing messages on this keyboard, but he accidentally shifted his hands either one key to the left or one key to the right. Because of this, the sequence of characters he typed does not...

Practice › Codeforces Solutions › Codeforces Round 258 (Div. 2) ›

CF 451B - Sort the Array

CF 451B - Sort the Array Rating: 1300 Tags: implementation, sortings Solve time: 1m 39s Verified: yes Solution Problem Understanding We are given an array of distinct integers. The task is to determine whether the entire array can become sorted in increasing order after reversing exactly one contiguous segment. If it is possible, we must print "yes" and one valid segment [l, r] whose reversal sorts the array. If it...

Practice › Codeforces Solutions › Codeforces Round 263 (Div. 1) ›

CF 461C - Appleman and a Sheet of Paper

CF 461C - Appleman and a Sheet of Paper Rating: 2200 Tags: data structures, implementation Solve time: 1m 22s Verified: no Solution Problem Understanding We have a one-dimensional sheet of paper represented as an array of width n . Appleman can fold the sheet at a position p , which means the left segment [0, p) flips and lies over the right segment [p, current_width) . After a fold, any...

Practice › Codeforces Solutions › Codeforces Round 264 (Div. 2) ›

CF 463D - Gargari and Permutations

CF 463D - Gargari and Permutations Rating: 1900 Tags: dfs and similar, dp, graphs, implementation Solve time: 58s Verified: yes Solution Problem Understanding We are given k permutations of the numbers from 1 to n . A permutation is simply a rearrangement of these numbers. Our goal is to find the length of the longest sequence of numbers that appears in the same relative order in all k permutations. In...

Practice › Codeforces Solutions › Codeforces Round 262 (Div. 2) ›

CF 460B - Little Dima and Equation

CF 460B - Little Dima and Equation Rating: 1500 Tags: brute force, implementation, math, number theory Solve time: 1m 6s Verified: yes Solution Problem Understanding The task asks us to find all positive integers less than one billion that satisfy the equation $$x = b \cdot s(x) \cdot a + c$$ where $a$, $b$, and $c$ are given constants, and $s(x)$ is the sum of the digits of $x$. The...

Practice › Codeforces Solutions ›

Codeforces Round 264 (Div. 2)

Codeforces Round 264 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1100-2100 | Time: 4m 50s Problem Name Rating Tags Solve Time Verified A Caisa and Sugar 1200 brute-force, implementation 1m ✓ B Caisa and Pylons 1100 brute-force, implementation, math 59s ✓ C Gargari and Bishops 1900 greedy, hashing, implementation 1m 6s ✓ D Gargari and Permutations 1900 dfs-and-similar, dp, graphs 58s ✓ E...

Practice › Codeforces Solutions ›

Codeforces Round 258 (Div. 2)

Codeforces Round 258 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 900-2300 | Time: 8m 33s Problem Name Rating Tags Solve Time Verified A Game With Sticks 900 implementation 1m 19s ✓ B Sort the Array 1300 implementation, sortings 1m 39s ✓ C Predict Outcome of the Game 1700 brute-force, implementation, math 1m 55s ✓ D Count Good Substrings 2000 math 2m 3s ✓...

Practice › Codeforces Solutions › Codeforces Round 257 (Div. 2) ›

CF 450B - Jzzhu and Sequences

CF 450B - Jzzhu and Sequences Rating: 1300 Tags: implementation, math Solve time: 51s Verified: yes Solution Problem Understanding The problem defines a linear sequence $f_n$ with two initial values $x = f_1$ and $y = f_2$, and a recurrence that repeats every six terms: $f_{n} = f_{n-1} - f_{n-2}$. Effectively, this creates a sequence with the following cycle: $f_1 = x$ $f_2 = y$ $f_3 = y - x$...

Practice › Codeforces Solutions › Codeforces Round 271 (Div. 2) ›

CF 474B - Worms

CF 474B - Worms Rating: 1200 Tags: binary search, implementation Solve time: 1m 36s Verified: yes Solution Problem Understanding We are given several piles of worms arranged in order. The worms are numbered consecutively across all piles. If the pile sizes are: 2 7 3 then the first pile contains worms numbered 1 through 2, the second pile contains worms numbered 3 through 9, and the third pile contains worms...

Practice › Codeforces Solutions › Codeforces Round 268 (Div. 2) ›

CF 469B - Chat Online

CF 469B - Chat Online Rating: 1300 Tags: implementation Solve time: 1m 14s Verified: yes Solution Problem Understanding We are asked to count how many different moments in time Little X can wake up such that he overlaps with Little Z online. Little Z has a fixed schedule consisting of multiple segments. Little X has a schedule defined relative to his wake-up time: if he wakes at time t ,...

Practice › Codeforces Solutions › Codeforces Round 268 (Div. 2) ›

CF 469A - I Wanna Be the Guy

CF 469A - I Wanna Be the Guy Rating: 800 Tags: greedy, implementation Solve time: 1m 38s Verified: yes Solution Problem Understanding We have a game with levels numbered from 1 to n . Little X can complete some subset of these levels, and Little Y can complete another subset. They decide to cooperate, which means a level is considered passable if at least one of them can complete it....

Practice › Codeforces Solutions › Codeforces Round 266 (Div. 2) ›

CF 466A - Cheap Travel

CF 466A - Cheap Travel Rating: 1200 Tags: implementation Solve time: 54s Verified: yes Solution Problem Understanding Ann needs to commute using the subway a total of n times. She can pay for each ride individually at a cost of a rubles, or she can buy a special multi-ride ticket that covers exactly m rides and costs b rubles. The problem asks us to determine the minimum total cost she...

Practice › Codeforces Solutions ›

Bayan 2015 Contest Warm Up

Bayan 2015 Contest Warm Up Type: Special | Problems: 6 | Verified: 4/6 | Rating range: 1100-2900 | Time: 11m 19s Problem Name Rating Tags Solve Time Verified A Bayan Bus 1100 implementation 1m 59s ✓ B Strongly Connected City 1400 brute-force, dfs-and-similar, graphs 59s ✓ C Kamal-ol-molk's Painting 2100 brute-force, constructive-algorithms, greedy 2m 56s ✗ D CGCDSSQ 2000 brute-force, data-structures, math 1m 11s ✓ E Strongly Connected City 2...

Practice › Codeforces Solutions ›

Codeforces Round 263 (Div. 2)

Codeforces Round 263 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1300 | Time: 2m 11s Problem Name Rating Tags Solve Time Verified A Appleman and Easy Task 1000 brute-force, implementation 1m 2s ✓ B Appleman and Card Game 1300 greedy 1m 9s ✓

Practice › Codeforces Solutions ›

Codeforces Round 257 (Div. 2)

Codeforces Round 257 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1300 | Time: 2m 25s Problem Name Rating Tags Solve Time Verified A Jzzhu and Children 1000 implementation 1m 34s ✓ B Jzzhu and Sequences 1300 implementation, math 51s ✓

Practice › Codeforces Solutions › Codeforces Round 164 (Div. 2) ›

CF 268C - Beautiful Sets of Points

CF 268C - Beautiful Sets of Points Rating: 1500 Tags: constructive algorithms, implementation Solve time: 1m 33s Verified: no Solution Problem Understanding We are asked to construct a set of points on a 2D integer grid with coordinates between 0 and n along the x-axis and 0 and m along the y-axis, excluding the origin (0,0). The set must satisfy the property that the Euclidean distance between any two points...

Practice › Codeforces Solutions › RCC 2014 Warmup (Div. 2) ›

CF 417B - Crash

CF 417B - Crash Rating: 1400 Tags: implementation Solve time: 1m 29s Verified: yes Solution Problem Understanding We are given a list of submissions made by participants in a programming contest. Each submission is described by two numbers: x , which counts how many unique solutions this participant had already submitted before this one, and k , the participant's ID. Submissions for the same participant must appear in chronological order:...

Practice › Codeforces Solutions › Codeforces Round 134 (Div. 2) ›

CF 218B - Airport

CF 218B - Airport Rating: 1100 Tags: implementation Solve time: 1m 24s Verified: no Solution Problem Understanding The airport has multiple planes, each with a certain number of empty seats. Every passenger in a queue can choose any plane to buy a ticket from, and the cost of the ticket equals the number of currently empty seats in that plane at the time of purchase. We are asked to compute...

Practice › Codeforces Solutions › Bayan 2012-2013 Elimination Round (ACM ICPC Rules, English statements) ›

CF 241C - Mirror Box

CF 241C - Mirror Box Rating: 2000 Tags: geometry, implementation Solve time: 1m 27s Verified: no Solution Problem Understanding The system describes a rectangular box where a laser beam enters through one small hole on the left wall and must exit through another hole on the right wall. Inside the box, there are horizontal mirror segments placed either on the floor or on the ceiling. Each mirror covers a segment...

Practice › Codeforces Solutions › Codeforces Round 203 (Div. 2) ›

CF 350A - TL

CF 350A - TL Rating: 1200 Tags: brute force, greedy, implementation Solve time: 6m 57s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 156 (Div. 2) ›

CF 255B - Code Parsing

CF 255B - Code Parsing Rating: 1200 Tags: implementation Solve time: 2m 19s Verified: yes Solution Problem Understanding We are given a string consisting solely of the characters "x" and "y". Two operations can be applied repeatedly in a specific order. The first operation swaps a consecutive "y" followed by "x" into "x" then "y". The second operation removes a consecutive "x" followed by "y". The string is processed greedily:...

Practice › Codeforces Solutions › Codeforces Round 247 (Div. 2) ›

CF 431C - k-Tree

CF 431C - k-Tree Rating: 1600 Tags: dp, implementation, trees Solve time: 1m 31s Verified: yes Solution Problem Understanding We are working with a rooted infinite tree where every node always has exactly $k$ outgoing edges to children. Each of those $k$ edges has a fixed weight: the first is 1, the second is 2, and so on up to $k$. From the root, we consider downward paths that move...

Practice › Codeforces Solutions › Codeforces Round 178 (Div. 2) ›

CF 294A - Shaass and Oskols

CF 294A - Shaass and Oskols Rating: 800 Tags: implementation, math Solve time: 1m 38s Verified: yes Solution Problem Understanding We have several wires stacked vertically. Each wire contains some birds sitting in a row from left to right. Every shot targets exactly one bird on one wire. When a bird on wire x is shot at position y , three things happen immediately: The bird itself disappears. Every bird...

Practice › Codeforces Solutions › Codeforces Round 182 (Div. 2) ›

CF 302A - Eugeny and Array

CF 302A - Eugeny and Array Rating: 800 Tags: implementation Solve time: 1m 32s Verified: yes Solution Problem Understanding We are given an array containing only 1 and -1 . For every query [l, r] , we look at the subarray from index l to r . We are allowed to rearrange the elements inside that subarray in any order, and we must decide whether it is possible for the...

Practice › Codeforces Solutions › Croc Champ 2012 - Qualification Round ›

CF 172A - Phone Code

CF 172A - Phone Code Rating: 800 Tags: *special, brute force, implementation Solve time: 3m Verified: yes Solution Problem Understanding We are given a list of phone numbers from friends in a city. Each phone number is a string of digits, and all numbers have the same length. The task is to find the city phone code, which Polycarpus defines as the longest common prefix shared by all these numbers....

Practice › Codeforces Solutions › Codeforces Round 100 ›

CF 140B - New Year Cards

CF 140B - New Year Cards Rating: 1800 Tags: brute force, greedy, implementation Solve time: 2m 41s Verified: no Solution Problem Understanding Alexander receives cards from friends one by one. Friend i sends card i , so card numbers and friend numbers are the same thing. At any moment Alexander may decide to send cards to some friends. He never creates new cards, he only reuses cards he has already...

Practice › Codeforces Solutions › Codeforces Round 160 (Div. 2) ›

CF 262A - Roma and Lucky Numbers

CF 262A - Roma and Lucky Numbers Rating: 800 Tags: implementation Solve time: 3m 6s Verified: no Solution Problem Understanding Roma has a collection of positive integers, and he is fascinated with numbers whose decimal digits consist only of 4 and 7. These are called lucky numbers. The task is to determine, from his collection, how many numbers have at most k lucky digits. The input gives the size of...

Practice › Codeforces Solutions ›

Codeforces Round 102 (Div. 1)

Codeforces Round 102 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1600-3000 | Time: 13m 21s Problem Name Rating Tags Solve Time Verified A Help Farmer 1600 brute-force, math 1m 53s ✓ B Help General 1800 constructive-algorithms, greedy, implementation 1m 38s ✓ C Help Caretaker 2300 brute-force, dp 1m 30s ✓ D Help Shrek and Donkey 2 2600 games 2m 34s ✓ E Help...

Practice › Codeforces Solutions › Codeforces Round 126 (Div. 2) ›

CF 200E - Tractor College

CF 200E - Tractor College Rating: 2400 Tags: implementation, math, number theory, ternary search Solve time: 1m 46s Verified: yes Solution Problem Understanding We are given the final exam results of a college where every student receives exactly one of three grades: 3, 4, or 5. Every student with the same grade must receive the same scholarship amount. If we denote these amounts as k3 , k4 , and k5...

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Codeforces Round 103 (Div. 2)

Codeforces Round 103 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2200 | Time: 8m 5s Problem Name Rating Tags Solve Time Verified A Arrival of the General 800 implementation 1m 52s ✓ B Meeting 1300 implementation 1m 15s ✓ C Anagram Search 1500 implementation, strings 1m 23s ✓ D Missile Silos 1900 data-structures, dfs-and-similar, graphs 2m 10s ✓ E Competition 2200 data-structures, greedy...

Practice › Codeforces Solutions › Codeforces Round 156 (Div. 2) ›

CF 255A - Greg's Workout

CF 255A - Greg's Workout Rating: 800 Tags: implementation Solve time: 2m 19s Verified: yes Solution Problem Understanding Greg performs exercises in a fixed repeating order. The first exercise trains the chest, the second trains the biceps, the third trains the back, then the pattern repeats again: chest, biceps, back, and so on. We are given an array where the value at position i tells us how many repetitions Greg...

Practice › Codeforces Solutions › Codeforces Round 237 (Div. 2) ›

CF 404B - Marathon

CF 404B - Marathon Rating: 1500 Tags: implementation, math Solve time: 2m 40s Verified: no Solution Problem Understanding We are tracking a runner moving along the perimeter of a square of side length a , starting from the bottom-left corner (0, 0) and moving counter-clockwise. After every fixed distance d , we want to know the runner’s exact coordinates on the square boundary. The motion is continuous along the border....

Practice › Codeforces Solutions › Codeforces Round 135 (Div. 2) ›

CF 219B - Special Offer! Super Price 999 Bourles!

CF 219B - Special Offer! Super Price 999 Bourles! Rating: 1400 Tags: implementation Solve time: 1m 29s Verified: yes Solution Problem Understanding Polycarpus already knows the best regular price for his product, p . He is willing to reduce it by at most d bourles if that gives the final price a more attractive ending, specifically as many trailing nines as possible. A trailing nine means a digit 9 at...

Practice › Codeforces Solutions ›

Codeforces Round 163 (Div. 2)

Codeforces Round 163 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 2/4 | Rating range: 800-2500 | Time: 8m 10s Problem Name Rating Tags Solve Time Verified B Queue at the School 800 constructive-algorithms, graph-matchings, implementation 1m 21s ✓ C Below the Diagonal 2100 constructive-algorithms, greedy, math 2m 17s ✗ D BerDonalds 2400 graphs, math, shortest-paths 2m 9s ✗ E More Queries to Array... 2500 data-structures, math 2m...

Practice › Codeforces Solutions › Codeforces Round 186 (Div. 2) ›

CF 313A - Ilya and Bank Account

CF 313A - Ilya and Bank Account Rating: 900 Tags: implementation, number theory Solve time: 3m 1s Verified: no Solution Problem Understanding We are given an integer that represents a bank balance. This balance can be positive or negative, and we are allowed to perform at most one modification operation that consists of removing a single digit from the number. The twist is that the bank allows removing either the...

Practice › Codeforces Solutions ›

Codeforces Round 112 (Div. 2)

Codeforces Round 112 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1000-2200 | Time: 8m 54s Problem Name Rating Tags Solve Time Verified A Supercentral Point 1000 implementation 1m 52s ✗ B Burning Midnight Oil 1500 binary-search, implementation 1m 42s ✓ C Another Problem on Strings 1600 binary-search, brute-force, dp 1m 20s ✓ D Beard Graph 2100 data-structures, dsu, trees 2m 13s ✓ E...

Practice › Codeforces Solutions ›

Codeforces Round 138 (Div. 1)

Codeforces Round 138 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 3/4 | Rating range: 1700-3000 | Time: 8m 30s Problem Name Rating Tags Solve Time Verified A Bracket Sequence 1700 data-structures, expression-parsing, implementation 1m 41s ✓ B Two Strings 1900 data-structures, dp, strings 1m 42s ✓ C Partial Sums 1900 combinatorics, math, number-theory 1m 25s ✓ D Spider 3000 geometry, graphs 3m 42s ✗

Practice › Codeforces Solutions › Codeforces Round 198 (Div. 2) ›

CF 340C - Tourist Problem

CF 340C - Tourist Problem Rating: 1600 Tags: combinatorics, implementation, math Solve time: 4m 39s Verified: yes Solution Problem Understanding We are asked to compute the average distance a tourist would walk if they visited all destinations on a straight road in every possible order, starting from kilometer zero. Each destination is at a distinct, positive integer distance from the starting point. The input is a list of these distances,...

Practice › Codeforces Solutions › Codeforces Round 136 (Div. 2) ›

CF 221A - Little Elephant and Function

CF 221A - Little Elephant and Function Rating: 1000 Tags: implementation, math Solve time: 1m 10s Verified: yes Solution Problem Understanding We are given a recursive procedure that operates on a permutation of numbers from 1 to n . The function behaves like this: For f(x) , it first recursively processes the first x - 1 elements, then swaps positions x - 1 and x . If we call f(n)...

Practice › Codeforces Solutions › Codeforces Round 122 (Div. 2) ›

CF 194A - Exams

CF 194A - Exams Rating: 900 Tags: implementation, math Solve time: 1m 28s Verified: yes Solution Problem Understanding The author has to take n exams. Every exam receives an integer grade between 2 and 5 inclusive. A grade of 2 means the exam is failed and must be retaken. The total sum of all grades must equal exactly k . Among all possible assignments of grades whose sum is k...

Practice › Codeforces Solutions › Codeforces Round 104 (Div. 2) ›

CF 146A - Lucky Ticket

CF 146A - Lucky Ticket Rating: 800 Tags: implementation Solve time: 1m 10s Verified: yes Solution Problem Understanding We are asked to determine whether a ticket number is lucky. A lucky ticket number satisfies two conditions simultaneously. First, every digit of the number must be either 4 or 7. Second, the sum of the digits in the first half of the number must equal the sum of the digits in...

Practice › Codeforces Solutions › Codeforces Round 133 (Div. 2) ›

CF 216A - Tiling with Hexagons

CF 216A - Tiling with Hexagons Rating: 1200 Tags: implementation, math Solve time: 56s Verified: yes Solution Problem Understanding The floor is made from unit hexagonal tiles, and the whole hall itself forms a larger hexagon. The six sides of the hall contain a, b, c, a, b, c tiles respectively as we walk around the boundary. The task is to compute how many unit hexagonal tiles fit inside this...

Practice › Codeforces Solutions › Codeforces Round 116 (Div. 2, ACM-ICPC Rules) ›

CF 180F - Mathematical Analysis Rocks!

CF 180F - Mathematical Analysis Rocks! Rating: 1200 Tags: constructive algorithms, implementation, math Solve time: 1m 28s Verified: yes Solution Problem Understanding Every student points to exactly one best friend, and every student is pointed to by exactly one other student. That means the friendship relation forms a permutation p . On day 1, notebook i stays with student i . On every following day, notebooks move according to p...

Practice › Codeforces Solutions ›

Codeforces Round 128 (Div. 2)

Codeforces Round 128 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1200-2300 | Time: 6m 39s Problem Name Rating Tags Solve Time Verified A Two Problems 1200 brute-force, implementation 1m 6s ✓ B Game on Paper 1300 brute-force, implementation 1m 41s ✓ C Photographer 1400 greedy, sortings 1m 5s ✓ D Hit Ball 1700 geometry, implementation, math 1m 20s ✗ E Transportation 2300 greedy,...

Practice › Codeforces Solutions › Codeforces Beta Round 99 (Div. 2) ›

CF 139A - Petr and Book

CF 139A - Petr and Book Rating: 1000 Tags: implementation Solve time: 1m 26s Verified: yes Solution Problem Understanding Petr has a book with n pages. Starting from Monday, he reads a fixed number of pages each day of the week. The input gives those seven daily reading capacities in order from Monday to Sunday. We need to determine on which day Petr finishes the book. The answer is not...

Practice › Codeforces Solutions › Codeforces Round 244 (Div. 2) ›

CF 427A - Police Recruits

CF 427A - Police Recruits Rating: 800 Tags: implementation Solve time: 1m 22s Verified: yes Solution Problem Understanding We are given a sequence of events happening in time order in a city. Each event is either the arrival of one or more new police recruits, or the occurrence of a crime. When recruits arrive, they increase the number of available officers. When a crime occurs, it consumes exactly one currently...

Practice › Codeforces Solutions › Codeforces Round 117 (Div. 2) ›

CF 182A - Battlefield

CF 182A - Battlefield Rating: 2200 Tags: geometry, graphs, implementation, shortest paths Solve time: 3m 47s Verified: yes Solution Problem Understanding We are asked to simulate movement across a 2D plane from a starting point $A$ to a destination $B$ while avoiding a periodic laser. The laser alternates between charging and firing, with durations $a$ and $b$ seconds, respectively. During the firing phase, Vasya must be inside a trench to...

Practice › Codeforces Solutions › Codeforces Round 152 (Div. 2) ›

CF 248A - Cupboards

CF 248A - Cupboards Rating: 800 Tags: implementation Solve time: 1m 34s Verified: yes Solution Problem Understanding We are given a set of cupboards, each with two doors: left and right. Each door can be either open or closed. The initial state of each door is given in the input. Karlsson wants all left doors to be in the same position and all right doors to be in the same...

Practice › Codeforces Solutions ›

Codeforces Round 100

Codeforces Round 100 Type: Special | Problems: 6 | Verified: 3/6 | Rating range: 1700-2600 | Time: 12m 15s Problem Name Rating Tags Solve Time Verified A New Year Table 1700 geometry, math 1m 45s ✓ B New Year Cards 1800 brute-force, greedy, implementation 2m 41s ✗ C New Year Snowmen 1800 binary-search, data-structures, greedy 2m ✗ D New Year Contest 1800 greedy, sortings 1m 55s ✓ E New Year...

Practice › Codeforces Solutions › Codeforces Round 136 (Div. 1) ›

CF 220A - Little Elephant and Problem

CF 220A - Little Elephant and Problem Rating: 1300 Tags: implementation, sortings Solve time: 2m 48s Verified: yes Solution Problem Understanding We are given an array of integers that is supposed to be sorted in non-decreasing order. The Little Elephant suspects that at most one swap operation may have disturbed the array. Our task is to check whether the array can be restored to sorted order with zero or one...

Practice › Codeforces Solutions › Codeforces Round 128 (Div. 2) ›

CF 203B - Game on Paper

CF 203B - Game on Paper Rating: 1300 Tags: brute force, implementation Solve time: 1m 41s Verified: yes Solution Problem Understanding We have an n × n grid that starts completely white. Cells are painted black one by one, and every move paints a different cell. After each move, we want to know whether the board already contains a completely black 3 × 3 square. The task is to output...

Practice › Codeforces Solutions ›

Codeforces Round 236 (Div. 1)

Codeforces Round 236 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 0/2 | Rating range: 2300-2900 | Time: 1m 57s Problem Name Rating Tags Solve Time Verified D Beautiful Pairs of Numbers 2300 combinatorics, dp 51s ✗ E Two Rooted Trees 2900 data-structures, implementation, trees 1m 6s ✗

Practice › Codeforces Solutions › Coder-Strike 2014 - Round 1 ›

CF 412E - E-mail Addresses

CF 412E - E-mail Addresses Rating: 1900 Tags: implementation Solve time: 2m 37s Verified: no Solution Problem Understanding We are given a single long string made of lowercase letters, digits, and the characters '.' , '_' , and '@' . We need to consider every contiguous substring and decide whether it can be interpreted as a valid email address under a strict format, then count how many such substrings exist....

Practice › Codeforces Solutions › ABBYY Cup 3.0 - Finals (online version) ›

CF 331D1 - Escaping on Beaveractor

CF 331D1 - Escaping on Beaveractor Rating: 2400 Tags: dfs and similar, implementation Solve time: 3m 8s Verified: no Solution Problem Understanding We have a square campus with coordinates from (0, 0) to (b, b) . Inside the square there are several directed segments, called arrows. Every arrow is either horizontal or vertical, and no two arrows intersect or even touch. A Beaveractor starts at some point with an initial...

Practice › Codeforces Solutions › Coder-Strike 2014 - Round 1 ›

CF 412C - Pattern

CF 412C - Pattern Rating: 1200 Tags: implementation, strings Solve time: 2m Verified: no Solution Problem Understanding Each pattern is a string made of lowercase English letters and the wildcard character ? . A wildcard can represent any lowercase letter. Two patterns intersect if there exists at least one concrete string that matches both of them. For example, a?c and abc intersect because the string abc satisfies both patterns. On...

Practice › Codeforces Solutions › Codeforces Round 156 (Div. 2) ›

CF 255D - Mr. Bender and Square

CF 255D - Mr. Bender and Square Rating: 1800 Tags: binary search, implementation, math Solve time: 1m 19s Verified: yes Solution Problem Understanding We are asked to simulate the spread of a signal across an n × n grid. Initially, a single cell at row x and column y is turned on, and in each second, any cell that is side-adjacent to a turned-on cell also turns on. The goal...

Practice › Codeforces Solutions ›

RCC 2014 Warmup (Div. 2)

RCC 2014 Warmup (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1400-2400 | Time: 7m 19s Problem Name Rating Tags Solve Time Verified A Elimination 1500 dp, implementation, math 1m 39s ✓ B Crash 1400 implementation 1m 29s ✓ C Football 1400 constructive-algorithms, graphs, implementation 1m 49s ✓ D Cunning Gena 1900 bitmasks, dp, greedy 34s ✗ E Square Table 2400 constructive-algorithms, math, probabilities...

Practice › Codeforces Solutions › Codeforces Round 161 (Div. 2) ›

CF 263B - Squares

CF 263B - Squares Rating: 900 Tags: greedy, implementation, sortings Solve time: 3m 7s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 145 (Div. 2, ACM-ICPC Rules) ›

CF 234C - Weather

CF 234C - Weather Rating: 1300 Tags: dp, implementation Solve time: 1m 27s Verified: yes Solution Problem Understanding We are given an array of daily temperatures. We want the sequence to look like this: First, several consecutive negative values. Then, several consecutive positive values. Both parts must be non-empty, and zero is forbidden anywhere in the final sequence. The task is to change as few elements as possible so that...

Practice › Codeforces Solutions › Codeforces Round 132 (Div. 2) ›

CF 215A - Bicycle Chain

CF 215A - Bicycle Chain Rating: 900 Tags: brute force, implementation Solve time: 1m 25s Verified: yes Solution Problem Understanding We have two sets of bicycle gears. The front gears are attached to the pedals, and the rear gears are attached to the back wheel. If the chain connects front gear a[i] to rear gear b[j] , the resulting gear ratio is b[j] / a[i] . We only care about...

Practice › Codeforces Solutions › Codeforces Round 153 (Div. 1) ›

CF 251E - Tree and Table

CF 251E - Tree and Table Rating: 3000 Tags: dfs and similar, dp, implementation, trees Solve time: 1m 57s Verified: no Solution Problem Understanding We are given a tree with $2n$ nodes, and the goal is to place each node into a 2-row by $n$-column table so that each edge of the tree connects two cells sharing a side. Each node occupies exactly one cell, and each cell contains exactly...

Practice › Codeforces Solutions › Codeforces Round 156 (Div. 2) ›

CF 255E - Furlo and Rublo and Game

CF 255E - Furlo and Rublo and Game Rating: 2200 Tags: games, implementation, math Solve time: 1m 51s Verified: yes Solution Problem Understanding We have several independent piles of coins. A move picks one pile with size x and replaces it with some smaller value y such that $$x^{1/4} \le y \le x^{1/2}$$ and y < x . The player who cannot make a move loses. Since moves affect only...

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Codeforces Round 129 (Div. 2)

Codeforces Round 129 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 900-1400 | Time: 2m 24s Problem Name Rating Tags Solve Time Verified A Little Elephant and Rozdil 900 brute-force, implementation 54s ✓ B Little Elephant and Sorting 1400 brute-force, greedy 1m 30s ✓

Practice › Codeforces Solutions ›

Codeforces Round 138 (Div. 2)

Codeforces Round 138 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1100-1500 | Time: 2m 3s Problem Name Rating Tags Solve Time Verified A Parallelepiped 1100 brute-force, geometry, math 1m 1s ✓ B Array 1500 bitmasks, implementation, two-pointers 1m 2s ✓

Practice › Codeforces Solutions › Codeforces Round 104 (Div. 1) ›

CF 145A - Lucky Conversion

CF 145A - Lucky Conversion Rating: 1200 Tags: greedy, implementation Solve time: 2m 2s Verified: yes Solution Problem Understanding We are given two strings of equal length, both consisting only of the characters 4 and 7 . The goal is to transform the first string into the second using the fewest operations. There are two allowed operations. We may flip a single digit, changing 4 to 7 or 7 to...

Practice › Codeforces Solutions › RCC 2014 Warmup (Div. 2) ›

CF 417C - Football

CF 417C - Football Rating: 1400 Tags: constructive algorithms, graphs, implementation Solve time: 1m 49s Verified: yes Solution Problem Understanding We are asked to construct a complete record of matches between n teams, where every match has a winner and a loser, and no pair of teams plays more than once. The final condition we must satisfy is global: for every ordered pair of distinct teams (i, j) , team...

Practice › Codeforces Solutions › Codeforces Round 101 (Div. 2) ›

CF 141A - Amusing Joke

CF 141A - Amusing Joke Rating: 800 Tags: implementation, sortings, strings Solve time: 1m 31s Verified: yes Solution Problem Understanding We are given three uppercase strings. The first two strings are the names written on the door, and the third string is the pile of letters found the next morning after somebody mixed everything together. The task is to check whether the third string contains exactly the same letters as...

Practice › Codeforces Solutions › Codeforces Round 243 (Div. 2) ›

CF 426B - Sereja and Mirroring

CF 426B - Sereja and Mirroring Rating: 1300 Tags: implementation Solve time: 1m 37s Verified: yes Solution Problem Understanding We start with some small matrix b . One mirroring operation doubles its height. The top half stays unchanged, and the bottom half becomes the rows of the top half written in reverse order. For example, if the current matrix is: A B C after mirroring it becomes: A B C...

Practice › Codeforces Solutions › Croc Champ 2013 - Qualification Round ›

CF 291B - Command Line Arguments

CF 291B - Command Line Arguments Rating: 1300 Tags: *special, implementation, strings Solve time: 1m 26s Verified: yes Solution Problem Understanding We are given a single string representing a command line in a simplified Pindows operating system. Each "lexeme" in this command line is either a contiguous sequence of non-space characters or a sequence of characters enclosed in double quotes. The first lexeme is the program name, and all subsequent...

Practice › Codeforces Solutions › Codeforces Round 129 (Div. 1) ›

CF 204E - Little Elephant and Strings

CF 204E - Little Elephant and Strings Rating: 2800 Tags: data structures, implementation, string suffix structures, two pointers Solve time: 45s Verified: yes Solution Problem Understanding We are given a list of strings, and for each string, we need to count the number of its substrings that appear in at least k strings from the list. A substring is any contiguous segment of a string. For example, if the string...

Practice › Codeforces Solutions ›

Codeforces Round 114 (Div. 1)

Codeforces Round 114 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1600-3000 | Time: 10m 57s Problem Name Rating Tags Solve Time Verified A Wizards and Trolleybuses 1600 implementation, math 1m 40s ✓ B Wizards and Huge Prize 1800 dp, math, probabilities 1m 38s ✗ C Wizards and Numbers 2300 games, math 1m 39s ✗ D Wizards and Roads 3000 data-structures, divide-and-conquer, graph-matchings 2m...

Practice › Codeforces Solutions ›

Codeforces Round 248 (Div. 2)

Codeforces Round 248 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 0/1 | Rating range: 1100-1100 | Time: 1m 42s Problem Name Rating Tags Solve Time Verified A Kitahara Haruki's Gift 1100 brute-force, implementation 1m 42s ✗

Practice › Codeforces Solutions › Codeforces Round 172 (Div. 1) ›

CF 280E - Sequence Transformation

CF 280E - Sequence Transformation Rating: 3000 Tags: brute force, data structures, dp, implementation, math Solve time: 2m 3s Verified: no Solution Problem Understanding We are given a sorted sequence $x_1, x_2, \dots, x_n$. We want to construct another sequence $y_1, y_2, \dots, y_n$ such that every adjacent difference stays inside a fixed interval: $$a \le y_{i+1} - y_i \le b$$ and every value remains inside $[1, q]$. The cost...

Practice › Codeforces Solutions ›

Codeforces Round 107 (Div. 2)

Codeforces Round 107 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1200 | Time: 3m 17s Problem Name Rating Tags Solve Time Verified A Soft Drinking 800 implementation, math 1m 31s ✓ B Phone Numbers 1200 implementation, strings 1m 46s ✓

Practice › Codeforces Solutions › Codeforces Round 148 (Div. 2) ›

CF 239B - Easy Tape Programming

CF 239B - Easy Tape Programming Rating: 1500 Tags: brute force, implementation Solve time: 3m 32s Verified: no Solution Problem Understanding We are given a string consisting of digits, < , and > characters. Every query selects a substring and treats it as a standalone program in a tiny tape language. The interpreter keeps two pieces of state. The current position points to one character of the string, and the...

Practice › Codeforces Solutions › Codeforces Round 148 (Div. 1) ›

CF 238D - Tape Programming

CF 238D - Tape Programming Rating: 2900 Tags: data structures, implementation Solve time: 1m 30s Verified: yes Solution Problem Understanding We are given a sequence of characters consisting of digits 0-9 and the symbols < and > . This sequence is interpreted as a simple tape program. The interpreter has two pointers: the current character pointer (CP) and the direction pointer (DP). Initially, CP points at the first character and...

Practice › Codeforces Solutions ›

Codeforces Round 153 (Div. 1)

Codeforces Round 153 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 2/5 | Rating range: 1300-3000 | Time: 26m 57s Problem Name Rating Tags Solve Time Verified A Points on Line 1300 binary-search, combinatorics, two-pointers 1m 9s ✓ B Playing with Permutations 1800 implementation, math 8m 15s ✗ C Number Transformation 2000 dp, greedy, number-theory 14m 23s ✗ D Two Sets 2700 bitmasks, math 1m 13s ✓ E...

Practice › Codeforces Solutions › Codeforces Beta Round 99 (Div. 1) ›

CF 138A - Literature Lesson

CF 138A - Literature Lesson Rating: 1600 Tags: implementation Solve time: 2m Verified: yes Solution Problem Understanding Each poem is divided into quatrains, groups of four lines. Two lines rhyme if the suffix starting from the k-th vowel from the end is identical in both lines. For example, with k = 1 , we compare suffixes starting at the last vowel. With k = 2 , we compare suffixes starting...

Practice › Codeforces Solutions ›

April Fools Day Contest 2014

April Fools Day Contest 2014 Type: April Fools | Problems: 6 | Verified: 0/6 | Rating range: 1500-2200 | Time: 15m 44s Problem Name Rating Tags Solve Time Verified A The Great Game 1700 *special 4m 22s ✗ B Mysterious Language 1700 *special 57s ✗ D Big Data 1700 *special 1m 2s ✗ F 000001 1900 *special 6m 57s ✗ G On a plane 2200 *special, geometry 1m 53s ✗...

Practice › Codeforces Solutions ›

Codeforces Round 161 (Div. 2)

Codeforces Round 161 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 1/3 | Rating range: 800-2000 | Time: 5m 38s Problem Name Rating Tags Solve Time Verified A Beautiful Matrix 800 implementation 1m 31s ✗ C Circle of Numbers 2000 brute-force, dfs-and-similar, implementation 1m 10s ✓ D Cycle in Graph 1800 dfs-and-similar, graphs 2m 57s ✗

Practice › Codeforces Solutions ›

Codeforces Round 247 (Div. 2)

Codeforces Round 247 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2200 | Time: 8m 37s Problem Name Rating Tags Solve Time Verified A Black Square 800 implementation 1m 10s ✓ B Shower Line 1200 brute-force, implementation 1m 52s ✓ C k-Tree 1600 dp, implementation, trees 1m 31s ✓ D Random Task 2100 binary-search, bitmasks, combinatorics 2m 1s ✓ E Chemistry Experiment 2200 binary-search,...

Practice › Codeforces Solutions ›

Codeforces Round 182 (Div. 2)

Codeforces Round 182 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1200 | Time: 4m 57s Problem Name Rating Tags Solve Time Verified A Eugeny and Array 800 implementation 1m 32s ✓ B Eugeny and Play List 1200 binary-search, implementation, two-pointers 3m 25s ✓

Practice › Codeforces Solutions ›

Codeforces Round 197 (Div. 2)

Codeforces Round 197 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 800-800 | Time: 4m 3s Problem Name Rating Tags Solve Time Verified A Helpful Maths 800 greedy, implementation, sortings 4m 3s ✓

Practice › Codeforces Solutions › Codeforces Round 147 (Div. 2) ›

CF 237B - Young Table

CF 237B - Young Table Rating: 1500 Tags: implementation, sortings Solve time: 1m 59s Verified: no Solution Problem Understanding The shape of the table is fixed. Row lengths are non-increasing, so every row is no longer than the row above it. The cells contain all integers from 1 to s exactly once, where s is the total number of cells. We may swap the contents of any two cells. The...

Practice › Codeforces Solutions › RCC 2014 Warmup (Div. 2) ›

CF 417A - Elimination

CF 417A - Elimination Rating: 1500 Tags: dp, implementation, math Solve time: 1m 39s Verified: yes Solution Problem Understanding We are organizing a programming competition where the goal is to select at least $n \cdot m$ finalists. Participants can qualify in three ways: first, by winning one of the main elimination rounds, which has $c$ problems and produces $n$ winners; second, by winning one of the additional elimination rounds, which...

Practice › Codeforces Solutions ›

April Fools Day Contest 2013

April Fools Day Contest 2013 Type: April Fools | Problems: 4 | Verified: 3/4 | Rating range: 1400-2800 | Time: 6m 44s Problem Name Rating Tags Solve Time Verified C WTF? 1700 *special, graph-matchings, implementation 1m 31s ✓ D Orange 1400 *special, implementation 2m 11s ✗ E HQ 2500 *special, constructive-algorithms 1m 43s ✓ F Greedy Petya 2800 *special, dfs-and-similar, graphs 1m 19s ✓

Practice › Codeforces Solutions › Codeforces Round 142 (Div. 2) ›

CF 230B - T-primes

CF 230B - T-primes Rating: 1300 Tags: binary search, implementation, math, number theory Solve time: 55s Verified: yes Solution Problem Understanding We are asked to identify T-primes in a list of positive integers. A T-prime is defined as a number that has exactly three distinct positive divisors. Thinking about divisors, the only way a number can have exactly three is if it is the square of a prime number. For...

Practice › Codeforces Solutions › April Fools Day Contest 2013 ›

CF 290D - Orange

CF 290D - Orange Rating: 1400 Tags: *special, implementation Solve time: 2m 11s Verified: no Solution Problem Understanding We are given a string consisting of uppercase and lowercase English letters, and an integer k . The task is to modify the string so that exactly k characters become uppercase. The relative order of characters must stay unchanged, only the letter cases may change. The tricky part is that the original...

Practice › Codeforces Solutions › CROC-MBTU 2012, Elimination Round (ACM-ICPC) ›

CF 245F - Log Stream Analysis

CF 245F - Log Stream Analysis Rating: 2000 Tags: binary search, brute force, implementation, strings Solve time: 3m 5s Verified: yes Solution Problem Understanding We are given a chronologically ordered stream of log entries, where each entry has an exact timestamp down to the second and an associated message describing a program warning. The task is not to process the messages themselves, but to reason purely about the timing of...

Practice › Codeforces Solutions › Codeforces Round 205 (Div. 2) ›

CF 353C - Find Maximum

CF 353C - Find Maximum Rating: 1600 Tags: implementation, math, number theory Solve time: 1m 37s Verified: yes Solution Problem Understanding We are given an array a of n non-negative integers, and a number m specified as a binary string. Each integer in a represents a weight associated with a position, and for any number x between 0 and m inclusive, we can select positions where the bits of x...

Practice › Codeforces Solutions ›

Codeforces Round 198 (Div. 2)

Codeforces Round 198 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 1600-1600 | Time: 4m 39s Problem Name Rating Tags Solve Time Verified C Tourist Problem 1600 combinatorics, implementation, math 4m 39s ✓

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Coder-Strike 2014 - Finals (online edition, Div. 1)

Coder-Strike 2014 - Finals (online edition, Div. 1) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1000-2600 | Time: 8m 34s Problem Name Rating Tags Solve Time Verified A Start Up 1000 implementation 1m 24s ✓ B Online Meeting 1800 implementation 2m 4s ✗ C Bug in Code 1900 data-structures, graphs, implementation 1m 57s ✓ D Cup Trick 2200 data-structures 1m 9s ✓ E Playing the...

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ABBYY Cup 2.0 - Easy

ABBYY Cup 2.0 - Easy Type: Special | Problems: 11 | Verified: 10/11 | Rating range: 800-2600 | Time: 24m 43s Problem Name Rating Tags Solve Time Verified A1 Good Matrix Elements 800 implementation 1m 37s ✗ A2 Good Matrix Elements 800 implementation 3m 13s ✓ B1 Rectangular Game 1000 number-theory 1m 36s ✓ B2 Rectangular Game 1200 number-theory 2m 20s ✓ C1 Party 1500 dfs-and-similar, dsu, graphs 3m 2s...

Practice › Codeforces Solutions › Codeforces Round 107 (Div. 2) ›

CF 151A - Soft Drinking

CF 151A - Soft Drinking Rating: 800 Tags: implementation, math Solve time: 1m 31s Verified: yes Solution Problem Understanding A group of friends wants to make identical toasts using three resources: soft drink, lime slices, and salt. Every toast consumes a fixed amount of each resource. The task is to determine how many complete toasts each friend can make before at least one resource runs out. The input gives the...

Practice › Codeforces Solutions › Codeforces Round 162 (Div. 1) ›

CF 264A - Escape from Stones

CF 264A - Escape from Stones Rating: 1200 Tags: constructive algorithms, data structures, implementation, two pointers Solve time: 1m 5s Verified: yes Solution Problem Understanding We start with a segment representing Liss’s current safe region, initially the interval from 0 to 1. Stones fall one after another, and each stone always lands exactly at the midpoint of Liss’s current interval. After each impact, Liss reacts by discarding either the left...

Practice › Codeforces Solutions › Codeforces Round 169 (Div. 2) ›

CF 276D - Little Girl and Maximum XOR

CF 276D - Little Girl and Maximum XOR Rating: 1700 Tags: bitmasks, dp, greedy, implementation, math Solve time: 1m 24s Verified: yes Solution Problem Understanding We are given two integers, l and r . We may choose any two numbers a and b such that both lie inside the interval [l, r] and a ≤ b . Among all such pairs, we must compute the maximum possible value of a...

Practice › Codeforces Solutions › Codeforces Round 242 (Div. 2) ›

CF 424A - Squats

CF 424A - Squats Rating: 900 Tags: implementation Solve time: 57s Verified: no Solution Problem Understanding We are given a row on size, showing the algorithm handles boundary constraints uniformly.

Practice › Codeforces Solutions › Codeforces Round 103 (Div. 2) ›

CF 144C - Anagram Search

CF 144C - Anagram Search Rating: 1500 Tags: implementation, strings Solve time: 1m 23s Verified: yes Solution Problem Understanding We are asked to count the number of substrings of a string s that can be transformed into an anagram of a given string p . The string s can contain question marks ? , which can be replaced by any lowercase letter. A substring is defined as a contiguous segment...

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Codeforces Round 146 (Div. 2)

Codeforces Round 146 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1300 | Time: 5m 12s Problem Name Rating Tags Solve Time Verified A Boy or Girl 800 brute-force, implementation, strings 3m 27s ✓ B Easy Number Challenge 1300 implementation, number-theory 1m 45s ✓

Practice › Codeforces Solutions › Codeforces Round 169 (Div. 2) ›

CF 276C - Little Girl and Maximum Sum

CF 276C - Little Girl and Maximum Sum Rating: 1500 Tags: data structures, greedy, implementation, sortings Solve time: 1m 42s Verified: yes Solution Problem Understanding We are given an array and several range queries. Each query asks for the sum of all elements between two indices. The unusual part is that we are allowed to rearrange the array before answering the queries, and we want the total of all query...

Practice › Codeforces Solutions › Croc Champ 2013 - Round 1 ›

CF 292A - SMSC

CF 292A - SMSC Rating: 1100 Tags: implementation Solve time: 1m 18s Verified: yes Solution Problem Understanding We are asked to simulate the operation of a short message service center (SMSC) that receives tasks, each consisting of a timestamp and a number of messages to send. Each second, if there are messages waiting in the queue, the SMSC sends exactly one message. Messages arriving at that same second cannot be...

Practice › Codeforces Solutions › Croc Champ 2012 - Qualification Round ›

CF 172C - Bus

CF 172C - Bus Rating: 1500 Tags: *special, implementation, sortings Solve time: 1m 19s Verified: yes Solution Problem Understanding We are asked to simulate the operation of a single bus that repeatedly transports students from a bus stop at coordinate 0 to their respective destinations along the positive axis. Each student arrives at the stop at a distinct time and has a fixed destination coordinate. The bus can carry at...

Practice › Codeforces Solutions › Codeforces Round 183 (Div. 1) ›

CF 303A - Lucky Permutation Triple

CF 303A - Lucky Permutation Triple Rating: 1300 Tags: constructive algorithms, implementation, math Solve time: 2m 15s Verified: no Solution Problem Understanding We are asked to construct three permutations $a$, $b$, and $c$ of length $n$ such that for every index $i$ the sum of $a[i]$ and $b[i]$ modulo $n$ equals $c[i]$ modulo $n$. Each permutation contains exactly the numbers from 0 to $n-1$ once, and the output must either...

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Codeforces Round 158 (Div. 2)

Codeforces Round 158 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 0/3 | Rating range: 1400-2100 | Time: 5m 48s Problem Name Rating Tags Solve Time Verified A Adding Digits 1400 implementation, math 1m 21s ✗ C Balls and Boxes 1700 constructive-algorithms, greedy, implementation 1m 20s ✗ D Black and White Tree 2100 constructive-algorithms, dsu, graphs 3m 7s ✗

Practice › Codeforces Solutions ›

Croc Champ 2013 - Round 1

Croc Champ 2013 - Round 1 Type: Special | Problems: 4 | Verified: 4/4 | Rating range: 1100-2000 | Time: 6m 34s Problem Name Rating Tags Solve Time Verified A SMSC 1100 implementation 1m 18s ✓ C Beautiful IP Addresses 2000 brute-force 1m 33s ✓ D Connected Components 1900 data-structures, dfs-and-similar, dp 1m 47s ✓ E Copying Data 1900 data-structures 1m 56s ✓

Practice › Codeforces Solutions › Codeforces Round 154 (Div. 2) ›

CF 253E - Printer

CF 253E - Printer Rating: 2200 Tags: binary search, data structures, implementation, sortings Solve time: 1m 1s Verified: yes Solution Problem Understanding We are simulating a single-threaded printer that receives tasks over time. Each task arrives at a given time, has a known number of pages, and a priority that determines the order in which it is served when multiple tasks are waiting. Higher priority tasks preempt lower priority ones....

Practice › Codeforces Solutions › Codeforces Round 236 (Div. 1) ›

CF 403E - Two Rooted Trees

CF 403E - Two Rooted Trees Rating: 2900 Tags: data structures, implementation, trees Solve time: 1m 6s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 117 (Div. 2) ›

CF 182B - Vasya's Calendar

CF 182B - Vasya's Calendar Rating: 1000 Tags: implementation Solve time: 3m 18s Verified: no Solution Problem Understanding We are asked to simulate a peculiar kind of calendar. Vasya has a clock that shows days from 1 to d . Each month has a certain number of days, and the clock does not know which month it is. When the month changes, if the clock’s day number does not match...

Practice › Codeforces Solutions › Coder-Strike 2014 - Finals (online edition, Div. 2) ›

CF 421A - Pasha and Hamsters

CF 421A - Pasha and Hamsters Rating: 800 Tags: constructive algorithms, implementation Solve time: 1m Verified: yes Solution Problem Understanding We are given a line of apples numbered from 1 to n. Each apple can be given to exactly one of two hamsters, Arthur or Alexander. The only restriction is that Arthur must receive only apples he likes, and Alexander must receive only apples he likes. Some apples may be...

Practice › Codeforces Solutions › Codeforces Round 163 (Div. 2) ›

CF 266B - Queue at the School

CF 266B - Queue at the School Rating: 800 Tags: constructive algorithms, graph matchings, implementation, shortest paths Solve time: 1m 21s Verified: yes Solution Problem Understanding We are given a queue made of boys and girls, represented as a string containing only B and G . Every second, each adjacent pair "BG" swaps positions and becomes "GB" . The swaps happen simultaneously. That detail matters a lot. If a boy...

Practice › Codeforces Solutions › ABBYY Cup 3.0 - Finals (online version) ›

CF 331E1 - Deja Vu

CF 331E1 - Deja Vu Rating: 2900 Tags: constructive algorithms, graphs, implementation Solve time: 6m 28s Verified: no Solution Problem Understanding We are given a directed graph of shops and streets. Every directed edge has an attached sequence of shop numbers called a vision. Whenever Neo traverses that edge, he sees exactly that sequence. Suppose Neo walks through a path $$p_0 \to p_1 \to p_2 \to \dots \to p_k$$ The...

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Surprise Language Round 6

Surprise Language Round 6 Type: Special | Problems: 4 | Verified: 4/4 | Rating range: 1300-1400 | Time: 6m 43s Problem Name Rating Tags Solve Time Verified B A + Reverse B 1300 *special, implementation 1m 55s ✓ C LCM 1400 *special, implementation, math 1m 59s ✓ E HQ9+ 1400 *special, implementation 1m 17s ✓ F Binary Notation 1400 *special, implementation 1m 32s ✓

Practice › Codeforces Solutions › Codeforces Round 102 (Div. 1) ›

CF 142B - Help General

CF 142B - Help General Rating: 1800 Tags: constructive algorithms, greedy, implementation Solve time: 1m 38s Verified: yes Solution Problem Understanding We have an n × m chessboard-like grid, and we want to place as many soldiers as possible. Two soldiers conflict if the squared Euclidean distance between their cells is exactly 5 . The only integer pairs whose squared distance equals 5 are (1, 2) and (2, 1) up...

Practice › Codeforces Solutions › Codeforces Round 108 (Div. 2) ›

CF 152B - Steps

CF 152B - Steps Rating: 1300 Tags: binary search, implementation Solve time: 1m 42s Verified: yes Solution Problem Understanding We have a rectangular grid with n rows and m columns. Vasya starts at position (xc, yc) . Then he processes k movement vectors one by one. For a vector (dx, dy) , he repeatedly moves: (x, y) -> (x + dx, y + dy) He keeps moving in that direction...

Practice › Codeforces Solutions › Codeforces Round 253 (Div. 2) ›

CF 443A - Anton and Letters

CF 443A - Anton and Letters Rating: 800 Tags: constructive algorithms, implementation Solve time: 1m 19s Verified: yes Solution Problem Understanding We are given a single formatted string that represents a set of lowercase English letters. The set is written in a very specific textual form: it starts with an opening brace, ends with a closing brace, and inside the braces letters are listed separated by comma and space. The...

Practice › Codeforces Solutions › Codeforces Round 172 (Div. 1) ›

CF 280B - Maximum Xor Secondary

CF 280B - Maximum Xor Secondary Rating: 1800 Tags: data structures, implementation, two pointers Solve time: 1m 35s Verified: yes Solution Problem Understanding We are given an array of distinct positive integers. For every subarray, we look at its largest value and its second largest value, then compute their XOR. Among all possible subarrays, we need the maximum such XOR value. The direct interpretation is simple: every subarray contributes exactly...

Practice › Codeforces Solutions › Croc Champ 2012 - Qualification Round ›

CF 172B - Pseudorandom Sequence Period

CF 172B - Pseudorandom Sequence Period Rating: 1200 Tags: *special, implementation, number theory Solve time: 3m 33s Verified: yes Solution Problem Understanding We are given a linear congruential generator, a classic pseudorandom sequence formula: $$r_i = (a \cdot r_{i-1} + b) \bmod m$$ The sequence starts from r0 , and every next value is computed from the previous one. Since every value is taken modulo m , there are only...

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Codeforces Round 235 (Div. 2)

Codeforces Round 235 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 2/3 | Rating range: 800-2000 | Time: 6m 53s Problem Name Rating Tags Solve Time Verified A Vanya and Cards 800 implementation, math 4m 10s ✗ B Sereja and Contests 1200 greedy, implementation, math 1m 24s ✓ D Roman and Numbers 2000 bitmasks, brute-force, combinatorics 1m 19s ✓

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Codeforces Round 256 (Div. 2)

Codeforces Round 256 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 2/3 | Rating range: 800-2200 | Time: 3m 43s Problem Name Rating Tags Solve Time Verified A Rewards 800 implementation 1m 14s ✓ D Multiplication Table 1800 binary-search, brute-force 1m 14s ✓ E Divisors 2200 brute-force, dfs-and-similar, implementation 1m 15s ✗

Practice › Codeforces Solutions › Codeforces Round 241 (Div. 2) ›

CF 416C - Booking System

CF 416C - Booking System Rating: 1600 Tags: binary search, dp, greedy, implementation Solve time: 1m 32s Verified: yes Solution Problem Understanding We are given a collection of booking requests, where each request represents a group of guests who either all get seated together or do not come at all. Each request has a size, meaning how many people arrive, and a profit, meaning how much money the restaurant earns...

Practice › Codeforces Solutions › ABBYY Cup 2.0 - Easy ›

CF 177A2 - Good Matrix Elements

CF 177A2 - Good Matrix Elements Rating: 800 Tags: implementation Solve time: 3m 13s Verified: yes Solution Problem Understanding We are given a square matrix of size n × n , where n is guaranteed to be odd. Each cell of the matrix contains a non-negative integer. The task is to sum the "good" elements of this matrix. An element is considered good if it lies on the main diagonal,...

Practice › Codeforces Solutions › VK Cup 2012 Finals (unofficial online-version) ›

CF 212B - Polycarpus is Looking for Good Substrings

CF 212B - Polycarpus is Looking for Good Substrings Rating: 2300 Tags: bitmasks, hashing, implementation Solve time: 1m 54s Verified: yes Solution Problem Understanding We are given one long lowercase string s . For every query, we are also given a set of characters C . Among all substrings of s , we only care about those whose set of distinct characters is exactly C . From those substrings, we...

Practice › Codeforces Solutions › Codeforces Round 172 (Div. 2) ›

CF 281A - Word Capitalization

CF 281A - Word Capitalization Rating: 800 Tags: implementation, strings Solve time: 1m 15s Verified: yes Solution Problem Understanding We are given a single English word and need to modify it so that only the first character becomes uppercase. Every other character must stay exactly as it originally appeared. The input contains just one non-empty string. The string may already start with an uppercase letter, or it may start with...

Practice › Codeforces Solutions › Codeforces Round 118 (Div. 2) ›

CF 186A - Comparing Strings

CF 186A - Comparing Strings Rating: 1100 Tags: implementation, strings Solve time: 3m 47s Verified: yes Solution Problem Understanding We are given two strings representing the genomes of two dwarves. The goal is to determine whether these two genomes could belong to the same race under a very specific definition: the first genome can be transformed into the second genome by swapping exactly two characters in the first genome. The...

Practice › Codeforces Solutions › Codeforces Round 121 (Div. 2) ›

CF 192B - Walking in the Rain

CF 192B - Walking in the Rain Rating: 1100 Tags: brute force, implementation Solve time: 3m Verified: no Solution Problem Understanding We are asked to determine the number of days the opposition can walk along a boulevard of tiles before it becomes impossible due to the tiles being destroyed by rain. Each tile has a durability measured in days. On day aᵢ the tile is still intact, and on day...

Practice › Codeforces Solutions ›

Codeforces Round 204 (Div. 1)

Codeforces Round 204 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 1/2 | Rating range: 1800-2700 | Time: 4m 1s Problem Name Rating Tags Solve Time Verified A Jeff and Rounding 1800 dp, greedy, implementation 1m 37s ✗ D Jeff and Removing Periods 2700 data-structures 2m 24s ✓

Practice › Codeforces Solutions › April Fools Day Contest 2013 ›

CF 290C - WTF?

CF 290C - WTF? Rating: 1700 Tags: *special, graph matchings, implementation, trees Solve time: 1m 31s Verified: yes Solution Problem Understanding The statement is written as a LOLCODE program. The actual task is to understand what this program computes. The input is a sequence of digits between 0 and 9 , one per line. The program repeatedly reads numbers until it encounters 0 . During the process it maintains four...

Practice › Codeforces Solutions › Codeforces Round 155 (Div. 2) ›

CF 254E - Dormitory

CF 254E - Dormitory Rating: 2100 Tags: dp, implementation Solve time: 2m 32s Verified: no Solution Problem Understanding Vasya receives food every morning. The food from day i can only be eaten on day i or day i + 1 . Every day Vasya himself must consume exactly v kilograms. Besides that, some friends stay with him during certain intervals, and if Vasya decides to feed a friend on a...

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Croc Champ 2012 - Qualification Round

Croc Champ 2012 - Qualification Round Type: Special | Problems: 5 | Verified: 4/5 | Rating range: 800-2200 | Time: 11m 42s Problem Name Rating Tags Solve Time Verified A Phone Code 800 *special, brute-force, implementation 3m ✓ B Pseudorandom Sequence Period 1200 *special, implementation, number-theory 3m 33s ✓ C Bus 1500 *special, implementation, sortings 1m 19s ✓ D Calendar Reform 1500 *special, number-theory 1m 29s ✓ E BHTML+BCSS 2200...

Practice › Codeforces Solutions › Codeforces Round 152 (Div. 2) ›

CF 248D - Sweets for Everyone!

CF 248D - Sweets for Everyone! Rating: 2300 Tags: binary search, greedy, implementation Solve time: 3m 8s Verified: yes Solution Problem Understanding We are given a one-dimensional street made of n consecutive sections. Each section is either a house that must receive exactly one kilogram of sweets, a shop that can provide at most one kilogram of sweets, or empty space that only matters for movement. Movement happens step-by-step between...

Practice › Codeforces Solutions › Codeforces Round 137 (Div. 2) ›

CF 222B - Cosmic Tables

CF 222B - Cosmic Tables Rating: 1300 Tags: data structures, implementation Solve time: 1m 33s Verified: yes Solution Problem Understanding We have a matrix of integers and three kinds of operations applied to it repeatedly. One operation swaps two rows. Another swaps two columns. The third asks for the value currently visible at a specific row and column. The tricky part is that the matrix itself can be as large...

Practice › Codeforces Solutions ›

Codeforces Round 172 (Div. 1)

Codeforces Round 172 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 1/2 | Rating range: 1800-3000 | Time: 3m 38s Problem Name Rating Tags Solve Time Verified B Maximum Xor Secondary 1800 data-structures, implementation, two-pointers 1m 35s ✓ E Sequence Transformation 3000 brute-force, data-structures, dp 2m 3s ✗

Practice › Codeforces Solutions › MemSQL start[c]up Round 1 ›

CF 325A - Square and Rectangles

CF 325A - Square and Rectangles Rating: 1500 Tags: implementation Solve time: 4m 20s Verified: yes Solution Problem Understanding We are given up to five axis-aligned rectangles on a plane. Each rectangle is defined by its bottom-left and top-right coordinates. No two rectangles overlap, although they may touch at edges or corners. The task is to determine whether the union of these rectangles exactly forms a perfect square. This means...

Practice › Codeforces Solutions › Croc Champ 2012 - Round 1 ›

CF 173A - Rock-Paper-Scissors

CF 173A - Rock-Paper-Scissors Rating: 1300 Tags: implementation, math Solve time: 1m 40s Verified: yes Solution Problem Understanding In this problem, two players, Nikephoros and Polycarpus, play multiple rounds of rock-paper-scissors. Each player has a fixed sequence of moves that they cycle through as the rounds progress. The sequences can have different lengths, so after reaching the end of a sequence, a player wraps back to the beginning. A round...

Practice › Codeforces Solutions › Codeforces Round 162 (Div. 2) ›

CF 265B - Roadside Trees (Simplified Edition)

CF 265B - Roadside Trees (Simplified Edition) Rating: 1000 Tags: greedy, implementation Solve time: 1m 24s Verified: yes Solution Problem Understanding We have a sequence of trees along a straight street. Each tree has a certain height, and on top of each tree is a nut that Squirrel Liss wants to eat. Liss starts at the base of the first tree. She can move up or down by one unit...

Practice › Codeforces Solutions ›

Codeforces Round 150 (Div. 2)

Codeforces Round 150 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 900-1600 | Time: 4m 21s Problem Name Rating Tags Solve Time Verified A Dividing Orange 900 implementation 3m 13s ✗ B Undoubtedly Lucky Numbers 1600 bitmasks, brute-force, dfs-and-similar 1m 8s ✓

Practice › Codeforces Solutions › Codeforces Round 201 (Div. 2) ›

CF 347B - Fixed Points

CF 347B - Fixed Points Rating: 1100 Tags: brute force, implementation, math Solve time: 1m 42s Verified: yes Solution Problem Understanding We are given a permutation of length n , which means an array of integers where each number from 0 to n - 1 appears exactly once. In this array, a "fixed point" is an index where the value equals the index itself. The goal is to perform at...

Practice › Codeforces Solutions › Codeforces Round 248 (Div. 2) ›

CF 433A - Kitahara Haruki's Gift

CF 433A - Kitahara Haruki's Gift Rating: 1100 Tags: brute force, implementation Solve time: 1m 42s Verified: no Solution Problem Understanding We have a collection of apples where every apple weighs either 100 grams or 200 grams. The task is to split all apples into two groups so that both groups have exactly the same total weight. The input gives the number of apples and then the weight of each...

Practice › Codeforces Solutions › Codeforces Round 139 (Div. 2) ›

CF 225D - Snake

CF 225D - Snake Rating: 2200 Tags: bitmasks, dfs and similar, graphs, implementation Solve time: 58s Verified: yes Solution Problem Understanding We are asked to simulate the movement of a snake on a small grid and determine the minimal number of moves required for the snake to reach an apple. The grid contains walls, empty squares, the snake itself, and one apple. The snake is represented as consecutive numbered segments...

Practice › Codeforces Solutions › Codeforces Round 153 (Div. 2) ›

CF 252A - Little Xor

CF 252A - Little Xor Rating: 1100 Tags: brute force, implementation Solve time: 1m 21s Verified: no Solution Problem Understanding We are given a sequence of non-negative integers and we want to pick a contiguous block of elements such that when we take the bitwise XOR of everything inside that block, the result is as large as possible. The task is to return that maximum achievable XOR over all possible...

Practice › Codeforces Solutions › Codeforces Round 123 (Div. 2) ›

CF 195C - Try and Catch

CF 195C - Try and Catch Rating: 1800 Tags: expression parsing, implementation Solve time: 1m 8s Verified: yes Solution Problem Understanding The task is to simulate the exception-handling behavior of a simple programming language. The program consists of three types of statements: try , catch(type, message) , and throw(type) . Each try starts a new exception-handling block, and its corresponding catch closes the most recently opened try that has not...

Practice › Codeforces Solutions ›

Codeforces Beta Round 99 (Div. 2)

Codeforces Beta Round 99 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1600 | Time: 2m 53s Problem Name Rating Tags Solve Time Verified A Petr and Book 1000 implementation 1m 26s ✓ B Wallpaper 1600 implementation, math 1m 27s ✓

Practice › Codeforces Solutions › Codeforces Round 144 (Div. 2) ›

CF 233A - Perfect Permutation

CF 233A - Perfect Permutation Rating: 800 Tags: implementation, math Solve time: 1m 26s Verified: yes Solution Problem Understanding We need to construct a permutation of numbers from 1 to n with two conditions. The first condition is p[p[i]] = i for every position i . Applying the permutation twice must return us to the original index. This means every element points back to its partner. The second condition is...

Practice › Codeforces Solutions › Codeforces Round 175 (Div. 2) ›

CF 285B - Find Marble

CF 285B - Find Marble Rating: 1200 Tags: implementation Solve time: 58s Verified: yes Solution Problem Understanding We are given a row of positions from 1 to n, and each position currently holds a glass. A marble is initially hidden under the glass at position s. The only way the configuration changes is by applying a fixed rearrangement rule multiple times. One application of this rule simultaneously moves every glass:...

Practice › Codeforces Solutions ›

MemSQL start[c]up Round 1

MemSQL start[c]up Round 1 Type: Special | Problems: 2 | Verified: 2/2 | Rating range: 1500-2800 | Time: 6m 17s Problem Name Rating Tags Solve Time Verified A Square and Rectangles 1500 implementation 4m 20s ✓ E The Red Button 2800 combinatorics, dfs-and-similar, dsu 1m 57s ✓

Practice › Codeforces Solutions › Codeforces Round 127 (Div. 2) ›

CF 202A - LLPS

CF 202A - LLPS Rating: 800 Tags: binary search, bitmasks, brute force, greedy, implementation, strings Solve time: 1m 6s Verified: yes Solution Problem Understanding We are given a lowercase string and must choose some characters, in order, to form a subsequence that is both a palindrome and lexicographically as large as possible. A subsequence does not need to stay contiguous. We may skip characters, but the remaining characters must keep...

Practice › Codeforces Solutions › Codeforces Round 252 (Div. 2) ›

CF 441A - Valera and Antique Items

CF 441A - Valera and Antique Items Rating: 1000 Tags: implementation Solve time: 1m 21s Verified: yes Solution Problem Understanding Valera wants to buy exactly one antique item from a set of sellers. Each seller offers multiple items with a current auction price. Valera can only secure a deal if he offers strictly more than the current price of an item, and he has a fixed budget v . The...

Practice › Codeforces Solutions › Codeforces Round 111 (Div. 2) ›

CF 160C - Find Pair

CF 160C - Find Pair Rating: 1700 Tags: implementation, math, sortings Solve time: 1m 47s Verified: yes Solution Problem Understanding We are given an array of n integers. From this array, we form every ordered pair (a[i], a[j]) , including pairs where i = j . Since both positions are chosen independently, there are exactly n² pairs. All these pairs are sorted lexicographically. That means pairs are ordered first by...

Practice › Codeforces Solutions ›

Codeforces Round 105 (Div. 2)

Codeforces Round 105 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 800-1900 | Time: 9m 21s Problem Name Rating Tags Solve Time Verified A Insomnia cure 800 constructive-algorithms, implementation, math 1m 34s ✗ B Escape 1500 implementation, math 1m 12s ✓ C Terse princess 1700 constructive-algorithms, greedy 2m 14s ✗ D Bag of mice 1800 dp, games, math 1m 55s ✓ E Porcelain 1900...

Practice › Codeforces Solutions › Codeforces Round 251 (Div. 2) ›

CF 439A - Devu, the Singer and Churu, the Joker

CF 439A - Devu, the Singer and Churu, the Joker Rating: 900 Tags: greedy, implementation Solve time: 1m 12s Verified: yes Solution Problem Understanding The problem asks us to schedule an event where Devu, a singer, performs n songs of varying lengths, and Churu, a comedian, tells jokes of fixed 5-minute duration. Devu requires a mandatory 10-minute rest after each song except the last, while Churu can perform jokes at...

Practice › Codeforces Solutions › Testing Round 10 ›

CF 440B - Balancer

CF 440B - Balancer Rating: 1600 Tags: greedy, implementation Solve time: 1m 3s Verified: yes Solution Problem Understanding We are given a row of matchboxes, each containing some number of matches. The total number of matches is divisible by the number of boxes, so there exists a target configuration where every box ends up holding exactly the same number. The only allowed operation is moving a single match from one...

Practice › Codeforces Solutions › Codeforces Round 148 (Div. 2) ›

CF 239A - Two Bags of Potatoes

CF 239A - Two Bags of Potatoes Rating: 1200 Tags: greedy, implementation, math Solve time: 1m 23s Verified: yes Solution Problem Understanding We know the second bag contains y potatoes. The first bag originally contained some positive number x , but that value was lost. The only remaining information is that the total number of potatoes, x + y , was divisible by k and did not exceed n ....

Practice › Codeforces Solutions ›

Codeforces Round 118 (Div. 2)

Codeforces Round 118 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1100-1200 | Time: 6m 28s Problem Name Rating Tags Solve Time Verified A Comparing Strings 1100 implementation, strings 3m 47s ✓ B Growing Mushrooms 1200 greedy, sortings 2m 41s ✓

Practice › Codeforces Solutions › Codeforces Round 238 (Div. 2) ›

CF 405A - Gravity Flip

CF 405A - Gravity Flip Rating: 900 Tags: greedy, implementation, sortings Solve time: 6m 21s Verified: no Solution Problem Understanding We are given a row of vertical stacks of cubes, where each position holds a certain number of cubes. You can think of this as an array where each index represents a column and the value is its height. Initially, gravity acts downward, so cubes are stacked vertically inside each...

Practice › Codeforces Solutions › Codeforces Round 247 (Div. 2) ›

CF 431B - Shower Line

CF 431B - Shower Line Rating: 1200 Tags: brute force, implementation Solve time: 1m 52s Verified: yes Solution Problem Understanding We have exactly five students standing in a line for a shower. While one student is showering, the remaining students wait in line and talk in adjacent pairs. The first and second students talk, the third and fourth students talk, and so on. Every ordered pair of students has a...

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Codeforces Round 205 (Div. 2)

Codeforces Round 205 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1200-1600 | Time: 5m 32s Problem Name Rating Tags Solve Time Verified A Domino 1200 implementation, math 3m 55s ✓ C Find Maximum 1600 implementation, math, number-theory 1m 37s ✓

Practice › Codeforces Solutions ›

Croc Champ 2012 - Round 1

Croc Champ 2012 - Round 1 Type: Special | Problems: 5 | Verified: 3/5 | Rating range: 1300-2600 | Time: 10m 55s Problem Name Rating Tags Solve Time Verified A Rock-Paper-Scissors 1300 implementation, math 1m 40s ✓ B Chamber of Secrets 1800 dfs-and-similar, shortest-paths 1m 49s ✓ C Spiral Maximum 1900 brute-force, dp 2m 41s ✗ D Deputies 2500 constructive-algorithms, graphs, greedy 3m 4s ✓ E Camping Groups 2600 data-structures,...

Practice › Codeforces Solutions ›

Codeforces Round 150 (Div. 1)

Codeforces Round 150 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 2/5 | Rating range: 1600-3000 | Time: 11m 4s Problem Name Rating Tags Solve Time Verified A The Brand New Function 1600 bitmasks 1m 27s ✓ B Hydra 2000 graphs, sortings 3m 20s ✗ C Colorado Potato Beetle 2200 dfs-and-similar, implementation 1m 37s ✗ D Cubes 2700 data-structures, dp, geometry 3m 9s ✓ E Matrix 3000 data-structures...

Practice › Codeforces Solutions › Codeforces Round 155 (Div. 2) ›

CF 254B - Jury Size

CF 254B - Jury Size Rating: 1500 Tags: brute force, implementation Solve time: 14m 52s Verified: yes Solution Problem Understanding Each Olympiad happens on a fixed calendar date in 2013. Before that date, a group of jury members must work continuously for several days. If an Olympiad needs p people and t preparation days, then exactly p people are busy on each of the t days immediately before the Olympiad....

Practice › Codeforces Solutions › Codeforces Round 241 (Div. 2) ›

CF 416D - Population Size

CF 416D - Population Size Rating: 2400 Tags: greedy, implementation, math Solve time: 1m 23s Verified: yes Solution Problem Understanding We are given a sequence of length $n$, where each position is either a fixed positive integer or unknown (marked as $-1$). The task is to interpret this sequence as being formed by concatenating several arithmetic progressions, one after another. Within each segment, consecutive elements must differ by a constant...

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Codeforces Round 113 (Div. 2)

Codeforces Round 113 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1100-2500 | Time: 11m 49s Problem Name Rating Tags Solve Time Verified A Rank List 1100 binary-search, implementation, sortings 1m 31s ✓ B Polygons 2100 geometry, sortings 3m 7s ✓ C Median 1500 greedy, math, sortings 1m 37s ✓ D Shoe Store 2500 dp, graph-matchings, greedy 2m 34s ✓ E Tetrahedron 1500 dp,...

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Codeforces Round 166 (Div. 2)

Codeforces Round 166 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 3/4 | Rating range: 1300-2200 | Time: 7m 9s Problem Name Rating Tags Solve Time Verified B Prime Matrix 1300 binary-search, brute-force, math 1m 46s ✓ C Secret 1500 constructive-algorithms, implementation 1m 31s ✗ D Good Substrings 1800 data-structures, strings 1m 42s ✓ E Three Horses 2200 constructive-algorithms, math, number-theory 2m 10s ✓

Practice › Codeforces Solutions › Codeforces Round 205 (Div. 2) ›

CF 353A - Domino

CF 353A - Domino Rating: 1200 Tags: implementation, math Solve time: 3m 55s Verified: yes Solution Problem Understanding We are given a row of domino tiles. Each tile has two numbers: one on the top half and one on the bottom half. We are allowed to flip a tile, which swaps its top and bottom numbers. Each flip costs one unit of time. The goal is to make both the...

Practice › Codeforces Solutions › Codeforces Round 197 (Div. 2) ›

CF 339A - Helpful Maths

CF 339A - Helpful Maths Rating: 800 Tags: greedy, implementation, sortings, strings Solve time: 4m 3s Verified: yes Solution Problem Understanding We are given a single string that represents a sum of small integers. The expression is written using digits and plus signs, where every number is guaranteed to be either 1, 2, or 3. The task is to rearrange the numbers so that the resulting expression is sorted in...

Practice › Codeforces Solutions › Codeforces Round 183 (Div. 2) ›

CF 304B - Calendar

CF 304B - Calendar Rating: 1300 Tags: brute force, implementation Solve time: 3m 19s Verified: yes Solution Problem Understanding We are given two valid Gregorian calendar dates in the format yyyy:mm:dd . The task is to compute how many days lie between them. The Gregorian calendar has the familiar leap year rule: $\text{Leap year} \iff (y\bmod 400=0) \lor (y\bmod 4=0 \land y\bmod 100\neq 0)$ A leap year contains 366 days...

Practice › Codeforces Solutions › Bayan 2012-2013 Elimination Round (ACM ICPC Rules, English statements) ›

CF 241F - Race

CF 241F - Race Rating: 2300 Tags: brute force, implementation Solve time: 2m 26s Verified: yes Solution Problem Understanding The city is represented by a grid. Every cell is either a building, a street tile with a traversal cost from 1 to 9 , or a junction labeled by a lowercase letter. Movement rules are unusual. You can move only between adjacent cells that share an edge, but: moving from...

Practice › Codeforces Solutions › Codeforces Round 244 (Div. 2) ›

CF 427B - Prison Transfer

CF 427B - Prison Transfer Rating: 1100 Tags: data structures, implementation Solve time: 1m 33s Verified: yes Solution Problem Understanding We have a line of prisoners, and each prisoner has a crime severity value. We must choose exactly c consecutive prisoners for transfer. Every prisoner inside the chosen segment must have severity at most t . The task is simply to count how many contiguous segments of length c satisfy...

Practice › Codeforces Solutions › Codeforces Round 141 (Div. 2) ›

CF 228B - Two Tables

CF 228B - Two Tables Rating: 1400 Tags: brute force, implementation Solve time: 2m 19s Verified: yes Solution Problem Understanding We have two binary grids. A shift (x, y) means that cell (i, j) in the first grid is compared with cell (i + x, j + y) in the second grid. The score of a shift is the number of positions where both cells exist and both contain 1...

Practice › Codeforces Solutions › Codeforces Round 108 (Div. 2) ›

CF 152A - Marks

CF 152A - Marks Rating: 900 Tags: implementation Solve time: 1m 8s Verified: yes Solution Problem Understanding We are asked to find the number of students in a class who are the best in at least one subject. Each student has grades for multiple subjects, with each grade being a single-digit number between 1 and 9. The input represents the grades as a grid of size n by m ,...

Practice › Codeforces Solutions › Codeforces Round 176 (Div. 1) ›

CF 286B - Shifting

CF 286B - Shifting Rating: 2200 Tags: implementation Solve time: 1m 1s Verified: yes Solution Problem Understanding We are asked to construct a "beautiful permutation" of the integers from 1 to n , where n can be as large as one million. The permutation is built by repeatedly applying a block-cyclic left shift operation on increasing block sizes. Specifically, for each k from 2 to n , we divide the...

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Zepto Code Rush 2014

Zepto Code Rush 2014 Type: Special | Problems: 3 | Verified: 0/3 | Rating range: 1400-3000 | Time: 9m 32s Problem Name Rating Tags Solve Time Verified B Om Nom and Spiders 1400 implementation, math 3m 56s ✗ E Cardboard Box 2600 data-structures, greedy 1m 21s ✗ F Banners 3000 brute-force, data-structures, dp 4m 15s ✗

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Codeforces Round 203 (Div. 2)

Codeforces Round 203 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 1/4 | Rating range: 1200-2200 | Time: 17m 31s Problem Name Rating Tags Solve Time Verified A TL 1200 brute-force, greedy, implementation 6m 57s ✗ B Resort 1500 graphs 4m 28s ✗ C Bombs 1600 greedy, implementation, sortings 3m 48s ✓ E Wrong Floyd 2200 brute-force, constructive-algorithms, dfs-and-similar 2m 18s ✗

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Codeforces Round 141 (Div. 2)

Codeforces Round 141 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 2/4 | Rating range: 800-2100 | Time: 7m 21s Problem Name Rating Tags Solve Time Verified A Is your horseshoe on the other hoof? 800 implementation 2m 19s ✓ B Two Tables 1400 brute-force, implementation 2m 19s ✓ D Zigzag 2100 data-structures 1m 28s ✗ E The Road to Berland is Paved With Good Intentions 1900 2-sat,...

Practice › Codeforces Solutions › Zepto Code Rush 2014 ›

CF 436B - Om Nom and Spiders

CF 436B - Om Nom and Spiders Rating: 1400 Tags: implementation, math Solve time: 3m 56s Verified: no Solution Problem Understanding We have a rectangular grid representing the park. Some cells initially contain spiders, and each spider permanently moves in one fixed direction: left, right, up, or down. Every second, a spider moves to the adjacent cell in that direction. If it steps outside the grid, it disappears. Om Nom...

Practice › Codeforces Solutions › Codeforces Round 184 (Div. 2) ›

CF 305B - Continued Fractions

CF 305B - Continued Fractions Rating: 1700 Tags: brute force, implementation, math Solve time: 1m 25s Verified: yes Solution Problem Understanding We are given a rational number written as a normal fraction p / q , and another number written as a finite continued fraction. The continued fraction has the form: $$a_1 + \frac{1}{a_2 + \frac{1}{a_3 + \dots}}$$ We must determine whether both representations describe the same rational number. The...

Practice › Codeforces Solutions › VK Cup 2012 Qualification Round 1 ›

CF 158A - Next Round

CF 158A - Next Round Rating: 800 Tags: *special, implementation Solve time: 1m 29s Verified: yes Solution Problem Understanding We are given the final standings of a programming contest. The scores are already sorted in non-increasing order, meaning each participant has a score greater than or equal to the next participant. A participant advances to the next round if two conditions are true. Their score must be at least as...

Practice › Codeforces Solutions › Codeforces Round 174 (Div. 1) ›

CF 283A - Cows and Sequence

CF 283A - Cows and Sequence Rating: 1600 Tags: constructive algorithms, data structures, implementation Solve time: 1m 35s Verified: yes Solution Problem Understanding We maintain a dynamic sequence of integers. Initially the sequence contains only one value, 0 . Each operation changes the sequence in one of three ways. We may add some value x to the first a elements, append a new number to the end, or remove the...

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Testing Round 10

Testing Round 10 Type: Special | Problems: 1 | Verified: 1/1 | Rating range: 1600-1600 | Time: 1m 3s Problem Name Rating Tags Solve Time Verified B Balancer 1600 greedy, implementation 1m 3s ✓

Practice › Codeforces Solutions › Coder-Strike 2014 - Finals (online edition, Div. 1) ›

CF 420A - Start Up

CF 420A - Start Up Rating: 1000 Tags: implementation Solve time: 1m 24s Verified: yes Solution Problem Understanding We are asked to determine whether a given company name is symmetric with respect to a vertical mirror. In practical terms, we are given a single string consisting of uppercase English letters, and we need to check whether the string would appear identical if reflected in a mirror placed vertically along its...

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Codeforces Round 115

Codeforces Round 115 Type: Special | Problems: 5 | Verified: 5/5 | Rating range: 1400-3000 | Time: 9m 1s Problem Name Rating Tags Solve Time Verified A Robot Bicorn Attack 1400 brute-force, implementation 1m 3s ✓ B Plane of Tanks: Pro 1400 implementation 2m 15s ✓ C Geometry Horse 1600 greedy, implementation, sortings 1m 21s ✓ D Plane of Tanks: Duel 2400 brute-force, dp, math 2m 32s ✓ F Gnomes...

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Codeforces Round 174 (Div. 1)

Codeforces Round 174 (Div. 1) Type: Div. 1 | Problems: 3 | Verified: 2/3 | Rating range: 1600-2400 | Time: 5m 38s Problem Name Rating Tags Solve Time Verified A Cows and Sequence 1600 constructive-algorithms, data-structures, implementation 1m 35s ✓ C Coin Troubles 2100 dp 2m 22s ✗ D Cows and Cool Sequences 2400 dp, math, number-theory 1m 41s ✓

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Codeforces Round 104 (Div. 2)

Codeforces Round 104 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1300 | Time: 2m 40s Problem Name Rating Tags Solve Time Verified A Lucky Ticket 800 implementation 1m 10s ✓ B Lucky Mask 1300 brute-force, implementation 1m 30s ✓

Practice › Codeforces Solutions › Codeforces Round 153 (Div. 1) ›

CF 251B - Playing with Permutations

CF 251B - Playing with Permutations Rating: 1800 Tags: implementation, math Solve time: 8m 15s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 137 (Div. 2) ›

CF 222C - Reducing Fractions

CF 222C - Reducing Fractions Rating: 1800 Tags: implementation, math, number theory, sortings Solve time: 34s Verified: no Solution Problem-Type Check This is a Type C - Optimization problem. The task is to determine the maximum number of intersections among perpendiculars drawn from each of five points to lines formed by the other four points. Therefore, a complete proof must establish both an upper bound on the number of intersections...

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Codeforces Round 242 (Div. 2)

Codeforces Round 242 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 0/5 | Rating range: 900-2500 | Time: 20m 42s Problem Name Rating Tags Solve Time Verified A Squats 900 implementation 57s ✗ B Megacity 1200 binary-search, greedy, implementation 5m 55s ✗ C Magic Formulas 1600 math 6m ✗ D Biathlon Track 2300 binary-search, brute-force, constructive-algorithms 1m 21s ✗ E Colored Jenga 2500 dfs-and-similar, dp, probabilities 6m 29s...

Practice › Codeforces Solutions › VK Cup 2012 Qualification Round 1 ›

CF 158C - Cd and pwd commands

CF 158C - Cd and pwd commands Rating: 1400 Tags: *special, data structures, implementation Solve time: 1m 45s Verified: yes Solution Problem Understanding We need to simulate a tiny shell that supports only two commands. The command cd path changes the current directory. The path may be absolute, meaning it starts from the root / , or relative, meaning it starts from the current directory. Inside a path, the token...

Practice › Codeforces Solutions › Croc Champ 2012 - Round 2 (Unofficial Div. 2 Edition) ›

CF 181A - Series of Crimes

CF 181A - Series of Crimes Rating: 800 Tags: brute force, geometry, implementation Solve time: 2m 48s Verified: yes Solution Problem Understanding We are given a map of a city as an n × m grid, where each cell represents a district. Three of the districts have been robbed, marked by * , and all other districts are empty ( . ). The task is to determine the location of...

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Coder-Strike 2014 - Qualification Round

Coder-Strike 2014 - Qualification Round Type: Special | Problems: 1 | Verified: 0/1 | Rating range: 1700-1700 | Time: 11m 4s Problem Name Rating Tags Solve Time Verified C Kicker 1700 *special, implementation 11m 4s ✗

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Codeforces Round 186 (Div. 2)

Codeforces Round 186 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 1/3 | Rating range: 900-2300 | Time: 5m 39s Problem Name Rating Tags Solve Time Verified A Ilya and Bank Account 900 implementation, number-theory 3m 1s ✗ D Ilya and Roads 2100 dp 1m 30s ✓ E Ilya and Two Numbers 2300 constructive-algorithms, data-structures, dsu 1m 8s ✗

Practice › Codeforces Solutions › Codeforces Round 105 (Div. 2) ›

CF 148B - Escape

CF 148B - Escape Rating: 1500 Tags: implementation, math Solve time: 1m 12s Verified: yes Solution Problem Understanding We are asked to simulate a pursuit scenario between a princess and a dragon. The princess runs at a constant speed, and the dragon flies faster but only begins chasing after a delay. Each time the dragon catches up, the princess can drop a bijou to distract him. The dragon then returns...

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Bayan 2012-2013 Elimination Round (ACM ICPC Rules, English statements)

Bayan 2012-2013 Elimination Round (ACM ICPC Rules, English statements) Type: ICPC/IOI | Problems: 4 | Verified: 3/4 | Rating range: 1900-2900 | Time: 7m 47s Problem Name Rating Tags Solve Time Verified D Numbers 2900 - 2m 21s ✗ E Flights 2600 graphs, shortest-paths 1m 54s ✓ F Race 2300 brute-force, implementation 2m 26s ✓ G Challenging Balloons 1900 constructive-algorithms 1m 6s ✓

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Codeforces Round 165 (Div. 2)

Codeforces Round 165 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1100-1400 | Time: 3m 31s Problem Name Rating Tags Solve Time Verified A Fancy Fence 1100 geometry, implementation, math 1m 12s ✓ B Multithreading 1400 data-structures, greedy, implementation 2m 19s ✓

Practice › Codeforces Solutions › Codeforces Round 115 ›

CF 175B - Plane of Tanks: Pro

CF 175B - Plane of Tanks: Pro Rating: 1400 Tags: implementation Solve time: 2m 15s Verified: yes Solution LeetCode 2119 - A Number After a Double Reversal Problem Understanding The problem asks whether an integer remains unchanged after performing the digit reversal operation twice. A reversal operation takes the decimal representation of a number and reverses the order of its digits. Leading zeros are removed automatically because integers do not...

Practice › Codeforces Solutions › Codeforces Round 159 (Div. 2) ›

CF 257A - Sockets

CF 257A - Sockets Rating: 1100 Tags: greedy, implementation, sortings Solve time: 1m 10s Verified: yes Solution Problem Understanding Vasya has a set of electrical devices and a limited number of wall sockets in his flat. Additionally, he owns multiple supply-line filters, each of which provides extra sockets but occupies one itself when plugged in. The task is to determine the minimum number of supply-line filters Vasya needs to plug...

Practice › Codeforces Solutions › Codeforces Round 185 (Div. 1) ›

CF 311A - The Closest Pair

CF 311A - The Closest Pair Rating: 1300 Tags: constructive algorithms, implementation Solve time: 3m 3s Verified: yes Solution Problem Understanding We are given a set of points in a 2D plane, and we want to measure how quickly a specific closest-pair algorithm behaves on a worst-case input. The algorithm itself is a straightforward double loop over points sorted by x-coordinate, but it includes a pruning condition: once the horizontal...

Practice › Codeforces Solutions › Coder-Strike 2014 - Round 1 ›

CF 412A - Poster

CF 412A - Poster Rating: 900 Tags: greedy, implementation Solve time: 2m 3s Verified: no Solution Problem Understanding We are given a linear banner split into n fixed positions, and a cursor-like ladder that starts at position k. Each position corresponds to exactly one character of a target string, and we must eventually print that string left to right, one character per position. The only two things we are allowed...

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Codeforces Round 127 (Div. 2)

Codeforces Round 127 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1700 | Time: 4m 35s Problem Name Rating Tags Solve Time Verified A LLPS 800 binary-search, bitmasks, brute-force 1m 6s ✓ B Brand New Easy Problem 1700 brute-force 3m 29s ✓

Practice › Codeforces Solutions › Codeforces Round 249 (Div. 2) ›

CF 435A - Queue on Bus Stop

CF 435A - Queue on Bus Stop Rating: 1000 Tags: implementation Solve time: 1m 7s Verified: yes Solution Problem Understanding We have a line of people waiting at a bus stop, but they are organized into groups. Each group has a fixed number of people and stands consecutively in the queue. A bus comes that can carry at most m people, and the people enter in the order of their...

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Codeforces Round 126 (Div. 2)

Codeforces Round 126 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 3/3 | Rating range: 800-2400 | Time: 7m 2s Problem Name Rating Tags Solve Time Verified B Drinks 800 implementation, math 1m 33s ✓ C Football Championship 1800 brute-force, implementation 3m 43s ✓ E Tractor College 2400 implementation, math, number-theory 1m 46s ✓

Practice › Codeforces Solutions › Codeforces Round 137 (Div. 2) ›

CF 222A - Shooshuns and Sequence

CF 222A - Shooshuns and Sequence Rating: 1200 Tags: brute force, implementation Solve time: 1m 25s Verified: yes Solution Problem Understanding We have an array of integers and a strange operation that keeps the array length unchanged. In one operation, we look at the current k -th element, append a copy of it to the end, then remove the first element. Effectively, the array shifts left by one position, and...

Practice › Codeforces Solutions › Surprise Language Round 6 ›

CF 188E - HQ9+

CF 188E - HQ9+ Rating: 1400 Tags: *special, implementation Solve time: 1m 17s Verified: yes Solution Problem Understanding We are given a single string representing a program written in the joke language HQ9+. Most characters do nothing, but four specific uppercase characters are meaningful. The instruction H prints "Hello, World!" , the instruction Q prints the program itself, and the instruction 9 prints the lyrics of "99 Bottles of Beer"...

Practice › Codeforces Solutions › Codeforces Round 240 (Div. 2) ›

CF 415B - Mashmokh and Tokens

CF 415B - Mashmokh and Tokens Rating: 1500 Tags: binary search, greedy, implementation, math Solve time: 1m 7s Verified: yes Solution Problem Understanding Each day Mashmokh receives a pile of tokens, and at the end of that day he can exchange some of them for money using a fixed conversion rule. If he returns $w$ tokens, the money he gets depends only on how many full “blocks” of size $a$...

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Codeforces Round 164 (Div. 2)

Codeforces Round 164 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 3/4 | Rating range: 800-2300 | Time: 7m 8s Problem Name Rating Tags Solve Time Verified A Games 800 brute-force 1m 29s ✓ C Beautiful Sets of Points 1500 constructive-algorithms, implementation 1m 33s ✗ D Wall Bars 2300 dp 2m 21s ✓ E Playlist 2100 math, probabilities, sortings 1m 45s ✓

Practice › Codeforces Solutions › Codeforces Round 159 (Div. 2) ›

CF 257B - Playing Cubes

CF 257B - Playing Cubes Rating: 1300 Tags: games, greedy, implementation Solve time: 1m 23s Verified: yes Solution Problem Understanding We are asked to simulate a game between two players arranging colored cubes in a line. Petya wants to maximize the number of consecutive cubes of the same color, while Vasya wants to maximize the number of consecutive cubes of different colors. Petya moves first, and the total number of...

Practice › Codeforces Solutions › Codeforces Round 161 (Div. 2) ›

CF 263A - Beautiful Matrix

CF 263A - Beautiful Matrix Rating: 800 Tags: implementation Solve time: 1m 31s Verified: no Solution Problem Understanding We are given a fixed 5 by 5 grid that contains mostly zeros and exactly one cell containing a one. In one move, we are allowed to swap adjacent rows or swap adjacent columns. Each such swap moves the entire row or column by exactly one position. The goal is to move...

Practice › Codeforces Solutions › Codeforces Round 185 (Div. 2) ›

CF 312A - Whose sentence is it?

CF 312A - Whose sentence is it? Rating: 1100 Tags: implementation, strings Solve time: 3m 13s Verified: no Solution Problem Understanding Each input line represents a sentence from a chat log, and the task is to classify who likely said it based on simple pattern clues at the beginning and end of the string. A sentence is attributed to Freda if it ends with the substring "lala." . A sentence...

Practice › Codeforces Solutions › Codeforces Round 106 (Div. 2) ›

CF 149A - Business trip

CF 149A - Business trip Rating: 900 Tags: greedy, implementation, sortings Solve time: 1m 33s Verified: yes Solution Problem Understanding Petya can decide in which months he waters the flower. Each month contributes a fixed amount of growth, and skipping a month contributes nothing. The goal is to reach at least k centimeters of total growth while using as few months as possible. The input gives the required growth k...

Practice › Codeforces Solutions › VK Cup 2012 Qualification Round 1 ›

CF 158B - Taxi

CF 158B - Taxi Rating: 1100 Tags: *special, greedy, implementation Solve time: 1m 21s Verified: yes Solution Problem Understanding We have a collection of schoolchildren organized into groups, and each group wants to travel together in a taxi. Each group has between one and four children, and each taxi can carry at most four children. The goal is to determine the minimum number of taxis required to transport all groups...

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Testing Round 8

Testing Round 8 Type: Special | Problems: 2 | Verified: 0/2 | Rating range: 1500-1800 | Time: 3m 11s Problem Name Rating Tags Solve Time Verified A IQ Test 1800 implementation 1m 11s ✗ B Sheldon and Ice Pieces 1500 greedy 2m ✗

Practice › Codeforces Solutions › Codeforces Round 166 (Div. 2) ›

CF 271C - Secret

CF 271C - Secret Rating: 1500 Tags: constructive algorithms, implementation Solve time: 1m 31s Verified: no Solution Problem Understanding We are asked to distribute a collection of n words among k Keepers in such a way that every Keeper receives a subset of words satisfying three conditions. First, no two Keepers can share a word. Second, every word must be assigned to some Keeper. Third, the numbers of words assigned...

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Codeforces Round 125 (Div. 2)

Codeforces Round 125 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 900-1900 | Time: 3m 12s Problem Name Rating Tags Solve Time Verified A Hexadecimal's theorem 900 brute-force, constructive-algorithms, implementation 1m 37s ✓ B Special Olympics 1900 geometry 1m 35s ✗

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Coder-Strike 2014 - Round 1

Coder-Strike 2014 - Round 1 Type: Special | Problems: 4 | Verified: 1/4 | Rating range: 900-2000 | Time: 8m 35s Problem Name Rating Tags Solve Time Verified A Poster 900 greedy, implementation 2m 3s ✗ C Pattern 1200 implementation, strings 2m ✗ D Giving Awards 2000 dfs-and-similar 1m 55s ✓ E E-mail Addresses 1900 implementation 2m 37s ✗

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VK Cup 2012 Wild-card Round 1

VK Cup 2012 Wild-card Round 1 Type: Special | Problems: 10 | Verified: 9/10 | Rating range: 1100-2000 | Time: 16m 36s Problem Name Rating Tags Solve Time Verified A Pentagonal numbers 1100 *special, implementation 3m 10s ✓ B Binary notation 1800 *special 1m 20s ✓ C Prime factorization 1800 *special 1m 16s ✓ D Remove digits 1900 *special 1m 15s ✓ E HQ9+ 1800 *special 1m 9s ✓ F...

Practice › Codeforces Solutions › CROC-MBTU 2012, Final Round (Online version, Div. 2) ›

CF 250B - Restoring IPv6

CF 250B - Restoring IPv6 Rating: 1500 Tags: implementation, strings Solve time: 1m 5s Verified: yes Solution Problem Understanding An IPv6 address in its full form is a fixed structure made of eight blocks. Each block represents 16 bits and is written as exactly four hexadecimal characters, including leading zeros when necessary. The blocks are separated by colons, so a fully expanded address always has the same length pattern and...

Practice › Codeforces Solutions › Codeforces Round 106 (Div. 2) ›

CF 149B - Martian Clock

CF 149B - Martian Clock Rating: 1600 Tags: implementation Solve time: 1m 25s Verified: yes Solution Problem Understanding We are given a string representing a Martian time in the format "a:b", where a is the hour component and b is the minute component. Unlike Earth time in base 10, these strings could represent numbers in any numeral system with a base greater than 1. Our task is to identify all...

Practice › Codeforces Solutions › Codeforces Round 252 (Div. 2) ›

CF 441D - Valera and Swaps

CF 441D - Valera and Swaps Rating: 2100 Tags: constructive algorithms, dsu, graphs, implementation, math, string suffix structures Solve time: 1m 26s Verified: no Solution Problem Understanding We are given a permutation, which we can think of as a row of numbered positions, where each position contains a distinct value from 1 to n. A swap operation exchanges two positions, and after a sequence of swaps we obtain another permutation....

Practice › Codeforces Solutions › Codeforces Round 239 (Div. 1) ›

CF 407C - Curious Array

CF 407C - Curious Array Rating: 2500 Tags: brute force, combinatorics, implementation, math Solve time: 34s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 103 (Div. 2) ›

CF 144A - Arrival of the General

CF 144A - Arrival of the General Rating: 800 Tags: implementation Solve time: 1m 52s Verified: yes Solution Problem Understanding We have a line of soldiers, each with a height. The general only cares about two positions in the lineup. The tallest soldier must stand at the very front, and the shortest soldier must stand at the very end. The order of everyone else is irrelevant. In one second, we...

Practice › Codeforces Solutions › Codeforces Round 158 (Div. 2) ›

CF 260C - Balls and Boxes

CF 260C - Balls and Boxes Rating: 1700 Tags: constructive algorithms, greedy, implementation Solve time: 1m 20s Verified: no Solution Problem Understanding We are given the final state of a row of boxes after a very specific operation was applied exactly once in reverse history. Originally, each box contained some number of balls. One box was chosen, emptied completely, and its balls were redistributed one by one starting from the...

Practice › Codeforces Solutions › Codeforces Round 146 (Div. 2) ›

CF 236B - Easy Number Challenge

CF 236B - Easy Number Challenge Rating: 1300 Tags: implementation, number theory Solve time: 1m 45s Verified: yes Solution Problem Understanding We need to compute the sum of the number of divisors of every product i * j * k , where i ranges from 1 to a , j ranges from 1 to b , and k ranges from 1 to c . For each triple (i, j, k)...

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Codeforces Round 195 (Div. 2)

Codeforces Round 195 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 2100-2700 | Time: 6m 33s Problem Name Rating Tags Solve Time Verified D Vasily the Bear and Beautiful Strings 2100 combinatorics, math, number-theory 3m 11s ✓ E Vasily the Bear and Painting Square 2700 bitmasks, combinatorics, dp 3m 22s ✓

Practice › Codeforces Solutions › Codeforces Round 105 (Div. 2) ›

CF 148A - Insomnia cure

CF 148A - Insomnia cure Rating: 800 Tags: constructive algorithms, implementation, math Solve time: 1m 34s Verified: no Solution Problem Understanding The problem asks us to figure out how many dragons get affected by a princess who has a unique way of defending herself. She targets every k -th, l -th, m -th, and n -th dragon with different actions. The total number of dragons is d . The input...

Practice › Codeforces Solutions › Codeforces Round 130 (Div. 2) ›

CF 208D - Prizes, Prizes, more Prizes

CF 208D - Prizes, Prizes, more Prizes Rating: 1200 Tags: implementation Solve time: 1m 26s Verified: yes Solution Problem Understanding In this problem, we are asked to simulate Vasya's prize redemption strategy. Vasya collects points from chocolate bar wrappings over time. Each wrapping contributes a certain number of points, and the points accumulate sequentially. There is a fixed set of prizes, each with a known cost in points. Vasya uses...

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Codeforces Round 156 (Div. 2)

Codeforces Round 156 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2200 | Time: 10m 7s Problem Name Rating Tags Solve Time Verified A Greg's Workout 800 implementation 2m 19s ✓ B Code Parsing 1200 implementation 2m 19s ✓ C Almost Arithmetical Progression 1500 brute-force, dp 2m 19s ✓ D Mr. Bender and Square 1800 binary-search, implementation, math 1m 19s ✓ E Furlo and...

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Codeforces Round 106 (Div. 2)

Codeforces Round 106 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 900-2300 | Time: 8m 2s Problem Name Rating Tags Solve Time Verified A Business trip 900 greedy, implementation, sortings 1m 33s ✓ B Martian Clock 1600 implementation 1m 25s ✓ C Division into Teams 1500 greedy, math, sortings 1m 40s ✗ D Coloring Brackets 1900 dp 2m 8s ✓ E Martian Strings 2300...

Practice › Codeforces Solutions › Codeforces Round 243 (Div. 2) ›

CF 426A - Sereja and Mugs

CF 426A - Sereja and Mugs Rating: 800 Tags: implementation Solve time: 1m 20s Verified: yes Solution Problem Understanding We have a cup with capacity s and several mugs containing water. Players take turns choosing one non-empty mug and pouring all of its water into the cup. The cup starts empty and water is never removed. If at any moment the amount of water inside the cup becomes greater than...

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Codeforces Round 134 (Div. 2)

Codeforces Round 134 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 0/2 | Rating range: 1100-1100 | Time: 4m 13s Problem Name Rating Tags Solve Time Verified A Mountain Scenery 1100 brute-force, constructive-algorithms, implementation 2m 49s ✗ B Airport 1100 implementation 1m 24s ✗

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Coder-Strike 2014 - Round 2

Coder-Strike 2014 - Round 2 Type: Special | Problems: 5 | Verified: 4/5 | Rating range: 1200-2200 | Time: 9m 37s Problem Name Rating Tags Solve Time Verified A Data Recovery 1200 implementation 1m 42s ✓ B Spyke Chatting 1300 implementation 1m 48s ✗ C Jeopardy! 1400 greedy, math 2m 23s ✓ D 2048 2000 bitmasks, dp 2m 23s ✓ E Maze 2D 2200 data-structures, divide-and-conquer 1m 21s ✓

Practice › Codeforces Solutions ›

Codeforces Round 240 (Div. 2)

Codeforces Round 240 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 900-1500 | Time: 2m 30s Problem Name Rating Tags Solve Time Verified A Mashmokh and Lights 900 implementation 1m 23s ✓ B Mashmokh and Tokens 1500 binary-search, greedy, implementation 1m 7s ✓

Practice › Codeforces Solutions › Codeforces Round 141 (Div. 2) ›

CF 228A - Is your horseshoe on the other hoof?

CF 228A - Is your horseshoe on the other hoof? Rating: 800 Tags: implementation Solve time: 2m 19s Verified: yes Solution Problem Understanding Valera already owns four horseshoes, and each horseshoe has a color represented by an integer. He wants all four horseshoes to have distinct colors before going to the party. If some colors repeat, he must buy new horseshoes to replace the duplicates. The input consists of four...

Practice › Codeforces Solutions › Croc Champ 2012 - Round 1 ›

CF 173D - Deputies

CF 173D - Deputies Rating: 2500 Tags: constructive algorithms, graphs, greedy, implementation Solve time: 3m 4s Verified: yes Solution Problem Understanding We are asked to assign k deputies to n cities, with the condition that each deputy manages exactly three cities. The cities are placed on two sides of a river, and some pairs of cities are connected by bridges that span the river. No deputy may manage two cities...

Practice › Codeforces Solutions › Codeforces Round 112 (Div. 2) ›

CF 165B - Burning Midnight Oil

CF 165B - Burning Midnight Oil Rating: 1500 Tags: binary search, implementation Solve time: 1m 42s Verified: yes Solution Problem Understanding Vasya has to write at least n lines of code during one night. He starts with productivity v , meaning he writes v lines before the first tea break. After every break, his productivity drops by a factor of k , using integer division. The total number of lines...

Practice › Codeforces Solutions › Codeforces Round 256 (Div. 2) ›

CF 448A - Rewards

CF 448A - Rewards Rating: 800 Tags: implementation Solve time: 1m 14s Verified: yes Solution Problem Understanding We are given a fixed number of shelves and a collection of rewards split into two categories, cups and medals. Each category is further divided into three ranks, but for the placement logic those ranks do not matter beyond counting total items in each category. Each shelf has two structural constraints. It can...

Practice › Codeforces Solutions › Codeforces Round 125 (Div. 2) ›

CF 199A - Hexadecimal's theorem

CF 199A - Hexadecimal's theorem Rating: 900 Tags: brute force, constructive algorithms, implementation, number theory Solve time: 1m 37s Verified: yes Solution Problem Understanding We are given a single integer n , and the statement guarantees that n itself is a Fibonacci number. The task is to represent n as the sum of three Fibonacci numbers. The three values are allowed to repeat, and zero is also a valid Fibonacci...

Practice › Codeforces Solutions › Codeforces Round 140 (Div. 1) ›

CF 226C - Anniversary

CF 226C - Anniversary Rating: 2400 Tags: data structures, implementation, math, matrices, number theory Solve time: 2m 19s Verified: yes Solution Problem Understanding We are asked to work with a contiguous range of integers from l to r , and for every possible subset of size k within this range, we consider the Fibonacci numbers at positions given by the subset elements. Among all subsets, we must find the maximum...

Practice › Codeforces Solutions › Codeforces Round 256 (Div. 2) ›

CF 448E - Divisors

CF 448E - Divisors Rating: 2200 Tags: brute force, dfs and similar, implementation, number theory Solve time: 1m 15s Verified: no Solution Problem Understanding We are given a single starting integer $X$, and we repeatedly expand it into a sequence. One expansion step replaces every number in the sequence by all of its positive divisors, written in increasing order. After applying this operation $k$ times starting from the one-element sequence...

Practice › Codeforces Solutions › Codeforces Round 128 (Div. 2) ›

CF 203D - Hit Ball

CF 203D - Hit Ball Rating: 1700 Tags: geometry, implementation, math Solve time: 1m 20s Verified: no Solution Problem Understanding We are asked to simulate a three-dimensional billiard-like scenario where a ball travels inside a rectangular corridor with perfectly reflecting walls, floor, and ceiling. The corridor is infinite in the y direction, and the ball is initially placed at the center of the corridor, at a distance m from the...

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Croc Champ 2012 - Round 2 (Unofficial Div. 2 Edition)

Croc Champ 2012 - Round 2 (Unofficial Div. 2 Edition) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1300 | Time: 4m 22s Problem Name Rating Tags Solve Time Verified A Series of Crimes 800 brute-force, geometry, implementation 2m 48s ✓ B Number of Triplets 1300 binary-search, brute-force 1m 34s ✓

Practice › Codeforces Solutions › Codeforces Round 238 (Div. 2) ›

CF 405C - Unusual Product

CF 405C - Unusual Product Rating: 1600 Tags: implementation, math Solve time: 1m 27s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 246 (Div. 2) ›

CF 432A - Choosing Teams

CF 432A - Choosing Teams Rating: 800 Tags: greedy, implementation, sortings Solve time: 1m 21s Verified: yes Solution Problem Understanding We are given a set of students at a university, each with a record of how many times they have already participated in the ACM ICPC world championship. The head of the training center wants to form teams of exactly three students, and each team is required to participate in...

Practice › Codeforces Solutions › Codeforces Round 149 (Div. 2) ›

CF 242A - Heads or Tails

CF 242A - Heads or Tails Rating: 1100 Tags: brute force, implementation Solve time: 3m 26s Verified: yes Solution Problem Understanding We know how many times each player flipped a coin. Vasya flipped x times and Petya flipped y times. Every head gives one point, every tail gives nothing. Valera does not remember the exact final scores, but he remembers three facts. Vasya got at least a heads, Petya got...

Practice › Codeforces Solutions › Codeforces Round 242 (Div. 2) ›

CF 424B - Megacity

CF 424B - Megacity Rating: 1200 Tags: binary search, greedy, implementation, sortings Solve time: 5m 55s Verified: no Solution

Practice › Codeforces Solutions ›

Codeforces Round 236 (Div. 2)

Codeforces Round 236 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 1/4 | Rating range: 1100-2200 | Time: 11m 10s Problem Name Rating Tags Solve Time Verified A Nuts 1100 greedy, math 4m 11s ✗ B Trees in a Row 1400 brute-force, implementation 2m 19s ✗ D Upgrading Array 1800 dp, greedy, math 1m 3s ✓ E Strictly Positive Matrix 2200 graphs, math 3m 37s ✗

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CROC-MBTU 2012, Final Round (Online version, Div. 2)

CROC-MBTU 2012, Final Round (Online version, Div. 2) Type: Div. 2 | Problems: 5 | Verified: 2/5 | Rating range: 1000-2000 | Time: 11m 54s Problem Name Rating Tags Solve Time Verified A Paper Work 1000 greedy 3m 9s ✗ B Restoring IPv6 1500 implementation, strings 1m 5s ✓ C Movie Critics 1600 greedy 3m 12s ✗ D Building Bridge 1900 geometry, ternary-search, two-pointers 1m 13s ✓ E Mad Joe...

Practice › Codeforces Solutions › Codeforces Round 202 (Div. 2) ›

CF 349B - Color the Fence

CF 349B - Color the Fence Rating: 1700 Tags: data structures, dp, greedy, implementation Solve time: 2m 3s Verified: yes Solution Problem Understanding The problem presents a scenario where Igor wants to paint a number on a fence using a limited amount of paint. Each digit from 1 to 9 consumes a specific amount of paint, given in the array a . Igor cannot use zero. The goal is to...

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Codeforces Round 142 (Div. 2)

Codeforces Round 142 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1300 | Time: 4m 23s Problem Name Rating Tags Solve Time Verified A Dragons 1000 greedy, sortings 3m 28s ✓ B T-primes 1300 binary-search, implementation, math 55s ✓

Practice › Codeforces Solutions ›

Codeforces Round 183 (Div. 2)

Codeforces Round 183 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1200-1300 | Time: 5m 19s Problem Name Rating Tags Solve Time Verified A Pythagorean Theorem II 1200 brute-force, math 2m ✓ B Calendar 1300 brute-force, implementation 3m 19s ✓

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Codeforces Round 202 (Div. 2)

Codeforces Round 202 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 1700-1700 | Time: 2m 3s Problem Name Rating Tags Solve Time Verified B Color the Fence 1700 data-structures, dp, greedy 2m 3s ✓

Practice › Codeforces Solutions › CROC-MBTU 2012, Elimination Round (ACM-ICPC) ›

CF 245A - System Administrator

CF 245A - System Administrator Rating: 800 Tags: implementation Solve time: 3m 27s Verified: yes Solution Problem Understanding Polycarpus is running a simple monitoring routine for two servers, which we can call server a and server b . Each "ping" command sends exactly ten packets to one of the servers. The input tells us, for each ping, how many packets successfully reached the server and how many were lost. The...

Practice › Codeforces Solutions › Codeforces Round 107 (Div. 2) ›

CF 151B - Phone Numbers

CF 151B - Phone Numbers Rating: 1200 Tags: implementation, strings Solve time: 1m 46s Verified: yes Solution Problem Understanding Each friend has a phone book containing numbers written in the format XX-XX-XX . Every phone number belongs to exactly one of three categories. A taxi number uses the same digit everywhere. Examples are 11-11-11 or 55-55-55 . A pizza number is strictly decreasing when we read its digits from left...

Practice › Codeforces Solutions › Codeforces Round 145 (Div. 2, ACM-ICPC Rules) ›

CF 234G - Practice

CF 234G - Practice Rating: 1600 Tags: constructive algorithms, divide and conquer, implementation Solve time: 2m 54s Verified: no Solution Problem Understanding We are given a team of n football players, each with a unique number from 1 to n . The coach wants to organize practice games so that every pair of players has faced each other on opposing teams at least once. Each practice splits all players into...

Practice › Codeforces Solutions › Codeforces Round 102 (Div. 2) ›

CF 143B - Help Kingdom of Far Far Away 2

CF 143B - Help Kingdom of Far Far Away 2 Rating: 1200 Tags: implementation, strings Solve time: 2m 19s Verified: yes Solution Problem Understanding We are given a number as a string and must print it in a banking-style money format. The formatting rules combine several independent transformations. The integer part must contain commas every three digits, counting from the right. The fractional part must contain exactly two digits. If...

Practice › Codeforces Solutions › Codeforces Round 125 (Div. 1) ›

CF 198A - About Bacteria

CF 198A - About Bacteria Rating: 1700 Tags: implementation, math Solve time: 1m 28s Verified: yes Solution Problem Understanding We are asked to model the growth of bacteria under a specific rule. In the first experiment, each bacterium multiplies by a factor of k every second and then b extra bacteria appear due to some abnormal effect. Starting from a single bacterium, after n seconds there are exactly z bacteria....

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Codeforces Round 123 (Div. 2)

Codeforces Round 123 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 3/4 | Rating range: 1000-2000 | Time: 5m 40s Problem Name Rating Tags Solve Time Verified A Let's Watch Football 1000 binary-search, brute-force, math 1m 24s ✓ C Try and Catch 1800 expression-parsing, implementation 1m 8s ✓ D Analyzing Polyline 1900 geometry, math, sortings 1m 28s ✗ E Building Forest 2000 data-structures, dsu, graphs 1m 40s ✓

Practice › Codeforces Solutions › Codeforces Round 149 (Div. 2) ›

CF 242B - Big Segment

CF 242B - Big Segment Rating: 1100 Tags: implementation, sortings Solve time: 1m 12s Verified: yes Solution Problem Understanding We are given a list of segments on a number line, each defined by a left and right endpoint. The task is to find if there exists a single segment among them that fully contains every other segment. If such a segment exists, we should return its 1-based index; otherwise, we...

Practice › Codeforces Solutions › Codeforces Round 241 (Div. 2) ›

CF 416A - Guess a number!

CF 416A - Guess a number! Rating: 1400 Tags: greedy, implementation, two pointers Solve time: 1m 47s Verified: no Solution Problem Understanding We are given a sequence of statements about an unknown integer value $y$. Each statement restricts $y$ relative to some integer threshold $x$, and is either strict or non-strict. After each statement, we are also told whether that statement is true or false. The task is not to...

Practice › Codeforces Solutions › Codeforces Round 126 (Div. 2) ›

CF 200B - Drinks

CF 200B - Drinks Rating: 800 Tags: implementation, math Solve time: 1m 33s Verified: yes Solution Problem Understanding We are given several drinks, and each drink already contains some percentage of orange juice. Vasya mixes the same amount from every drink into one large cocktail. The task is to compute the final percentage of orange juice in the mixture. If one drink is 50% orange juice and another is 100%,...

Practice › Codeforces Solutions › Codeforces Round 117 (Div. 2) ›

CF 182D - Common Divisors

CF 182D - Common Divisors Rating: 1400 Tags: brute force, hashing, implementation, math, strings Solve time: 1m 36s Verified: yes Solution Problem Understanding We are given two lowercase strings. A string d is called a divisor of another string s if s can be formed by concatenating d several times in a row. For example, "ab" divides "ababab" because repeating "ab" three times gives the full string. On the other...

Practice › Codeforces Solutions ›

Codeforces Round 137 (Div. 2)

Codeforces Round 137 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 3/4 | Rating range: 1200-1900 | Time: 6m 42s Problem Name Rating Tags Solve Time Verified A Shooshuns and Sequence 1200 brute-force, implementation 1m 25s ✓ B Cosmic Tables 1300 data-structures, implementation 1m 33s ✓ C Reducing Fractions 1800 implementation, math, number-theory 34s ✗ E Decoding Genome 1900 dp, matrices 3m 10s ✓

Practice › Codeforces Solutions › Codeforces Round 103 (Div. 2) ›

CF 144B - Meeting

CF 144B - Meeting Rating: 1300 Tags: implementation Solve time: 1m 15s Verified: yes Solution Problem Understanding We are asked to determine how many generals need warm blankets at a rectangular table placed on an infinite Cartesian plane. The table corners are given by two points with integer coordinates, and each integer point along the perimeter of the rectangle hosts a general. There are a number of radiators, each with...

Practice › Codeforces Solutions › ABBYY Cup 3.0 ›

CF 316F3 - Suns and Rays

CF 316F3 - Suns and Rays Rating: 2200 Tags: constructive algorithms, dfs and similar, implementation Solve time: 2m Verified: no Solution Problem Understanding The input is a binary image, essentially a grid where each cell is either background or part of a drawn object. Inside this grid, there are multiple disjoint shapes called suns. Each sun is an elliptical blob of foreground pixels, possibly rotated, and from its boundary extend...

Practice › Codeforces Solutions › Codeforces Round 204 (Div. 2) ›

CF 352A - Jeff and Digits

CF 352A - Jeff and Digits Rating: 1000 Tags: brute force, implementation, math Solve time: 2m 26s Verified: yes Solution Problem Understanding We are given a multiset of cards, each card showing either the digit 0 or the digit 5. From these cards we may choose any subset and arrange the chosen digits into a number written in a single line. Our goal is to build the largest possible number...

Practice › Codeforces Solutions › Codeforces Round 113 (Div. 2) ›

CF 166A - Rank List

CF 166A - Rank List Rating: 1100 Tags: binary search, implementation, sortings Solve time: 1m 31s Verified: yes Solution Problem Understanding We are given the final results of a programming contest. Each team has two values attached to it: how many problems it solved and its total penalty time. The ranking rule is the standard ICPC-style ordering. A team ranks higher if it solved more problems. If two teams solved...

Practice › Codeforces Solutions › Codeforces Round 194 (Div. 1) ›

CF 333D - Characteristics of Rectangles

CF 333D - Characteristics of Rectangles Rating: 2100 Tags: binary search, bitmasks, brute force, implementation, sortings Solve time: 2m 12s Verified: no Solution Problem Understanding We are given a grid of integers. From this grid we may cut away some rows from the top and bottom, and some columns from the left and right. After cropping, the remaining part must still be a rectangle with at least two rows and...

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Codeforces Round 147 (Div. 2)

Codeforces Round 147 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 3/3 | Rating range: 1000-2000 | Time: 9m 35s Problem Name Rating Tags Solve Time Verified A Free Cash 1000 implementation 3m 17s ✓ C Primes on Interval 1600 binary-search, number-theory, two-pointers 4m 4s ✓ D T-decomposition 2000 dfs-and-similar, graphs, greedy 2m 14s ✓

Practice › Codeforces Solutions › Codeforces Round 115 ›

CF 175A - Robot Bicorn Attack

CF 175A - Robot Bicorn Attack Rating: 1400 Tags: brute force, implementation Solve time: 1m 3s Verified: yes Solution Problem Understanding We are given a string of digits, which represents the concatenation of the scores Vasya achieved in three rounds of Robot Bicorn Attack. Each round produces a non-negative integer not exceeding 1,000,000, and numbers cannot have leading zeros unless the number itself is zero. Vasya has lost the boundaries...

Practice › Codeforces Solutions › Codeforces Round 114 (Div. 1) ›

CF 167A - Wizards and Trolleybuses

CF 167A - Wizards and Trolleybuses Rating: 1600 Tags: implementation, math Solve time: 1m 40s Verified: yes Solution Problem Understanding Each trolleybus starts from the depot at a fixed departure time. It begins with speed 0 , can accelerate at most a , and can never exceed its own speed limit v[i] . The destination is d meters away. Braking is unrestricted, so a trolleybus can instantly reduce its speed...

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Codeforces Round 246 (Div. 2)

Codeforces Round 246 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-2300 | Time: 4m 1s Problem Name Rating Tags Solve Time Verified A Choosing Teams 800 greedy, implementation, sortings 1m 21s ✓ E Square Tiling 2300 constructive-algorithms, greedy 2m 40s ✓

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Testing Round 6

Testing Round 6 Type: Special | Problems: 4 | Verified: 1/4 | Rating range: 800-2300 | Time: 10m 15s Problem Name Rating Tags Solve Time Verified A Candies 800 implementation 3m 20s ✗ B Optimizer 2100 data-structures, greedy, sortings 1m 26s ✓ C White, Black and White Again 2100 combinatorics, number-theory 3m 20s ✗ D Polygon 2300 constructive-algorithms, geometry 2m 9s ✗

Practice › Codeforces Solutions › Codeforces Round 237 (Div. 2) ›

CF 404A - Valera and X

CF 404A - Valera and X Rating: 1000 Tags: implementation Solve time: 4m 55s Verified: no Solution Problem Understanding We are given a square grid of size $n \times n$, where $n$ is an odd integer. Each cell contains a lowercase English letter. The task is to determine whether the pattern of letters forms an “X” shape under a strict rule. The grid is considered valid if every cell on...

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CROC-MBTU 2012, Elimination Round (ACM-ICPC)

CROC-MBTU 2012, Elimination Round (ACM-ICPC) Type: ICPC/IOI | Problems: 8 | Verified: 8/8 | Rating range: 800-2200 | Time: 18m 42s Problem Name Rating Tags Solve Time Verified A System Administrator 800 implementation 3m 27s ✓ B Internet Address 1100 implementation, strings 1m 53s ✓ C Game with Coins 1700 greedy 1m 37s ✓ D Restoring Table 1500 constructive-algorithms, greedy 3m 10s ✓ E Mishap in Club 1400 greedy, implementation...

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VK Cup 2012 Qualification Round 2

VK Cup 2012 Qualification Round 2 Type: Special | Problems: 5 | Verified: 5/5 | Rating range: 1100-1700 | Time: 8m 47s Problem Name Rating Tags Solve Time Verified A Friends or Not 1400 *special, greedy, implementation 1m 47s ✓ B Matchmaker 1100 *special, greedy, sortings 2m 1s ✓ C String Manipulation 1.0 1400 *special, binary-search, brute-force 1m 31s ✓ D Palindrome pairs 1500 *special, brute-force, dp 1m 26s ✓...

Practice › Codeforces Solutions › Coder-Strike 2014 - Qualification Round ›

CF 411C - Kicker

CF 411C - Kicker Rating: 1700 Tags: *special, implementation Solve time: 11m 4s Verified: no Solution Problem Understanding We are given four players split into two fixed teams of two players each. Each player has two independent strengths: one for defence and one for attack. Before the match, each team must assign one of its players to attack and the other to defend. Once both teams have chosen roles, we...

Practice › Codeforces Solutions › Codeforces Round 136 (Div. 2) ›

CF 221B - Little Elephant and Numbers

CF 221B - Little Elephant and Numbers Rating: 1300 Tags: implementation Solve time: 2m 47s Verified: yes Solution Problem Understanding We are asked to count divisors of a given positive integer x that share at least one digit with x . In other words, we examine every number d that divides x evenly and check whether there exists a digit appearing both in x and in d . The input...

Practice › Codeforces Solutions › ABBYY Cup 3.0 - Finals (online version) ›

CF 331B1 - Shave Beaver!

CF 331B1 - Shave Beaver! Rating: 1700 Tags: implementation Solve time: 2m 32s Verified: yes Solution Problem Understanding We are given a permutation of numbers from 1 to n, and we repeatedly modify it by swapping positions. On top of that, we are asked queries about intervals of values, not positions. For a query of type 1, we pick a value range from x to y and want to know...

Practice › Codeforces Solutions › Codeforces Round 236 (Div. 2) ›

CF 402B - Trees in a Row

CF 402B - Trees in a Row Rating: 1400 Tags: brute force, implementation Solve time: 2m 19s Verified: no Solution

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Codeforces Round 104 (Div. 1)

Codeforces Round 104 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1200-2900 | Time: 10m 29s Problem Name Rating Tags Solve Time Verified A Lucky Conversion 1200 greedy, implementation 2m 2s ✓ B Lucky Number 2 1800 constructive-algorithms 2m 22s ✓ C Lucky Subsequence 2100 combinatorics, dp, math 2m 5s ✓ D Lucky Pair 2900 combinatorics, data-structures, implementation 1m 48s ✗ E Lucky Queries...

Practice › Codeforces Solutions › Codeforces Round 115 ›

CF 175F - Gnomes of Might and Magic

CF 175F - Gnomes of Might and Magic Rating: 3000 Tags: data structures, graphs, implementation, shortest paths Solve time: 1m 50s Verified: yes Solution Problem Understanding The kingdom of gnomes consists of castles connected by a very specific graph structure. There is a cycle of m castles called the Good Path, connected sequentially with roads and forming a closed loop. Between every pair of consecutive castles on this cycle, there...

Practice › Codeforces Solutions › Surprise Language Round 6 ›

CF 188B - A + Reverse B

CF 188B - A + Reverse B Rating: 1300 Tags: *special, implementation Solve time: 1m 55s Verified: yes Solution Problem Understanding We are asked to compute the sum of a number a and the reverse of another number b . Reversing a number means reading its digits from right to left and treating the result as an integer. For instance, reversing 230 yields 32 because leading zeros are discarded in...

Practice › Codeforces Solutions › Codeforces Round 138 (Div. 2) ›

CF 224B - Array

CF 224B - Array Rating: 1500 Tags: bitmasks, implementation, two pointers Solve time: 1m 2s Verified: yes Solution Problem Understanding We are given an array of integers and a number k . The task is to find a contiguous subarray, or segment, such that it contains exactly k distinct integers. Among all segments that satisfy this condition, we are asked to find one that is minimal by inclusion , meaning...

Practice › Codeforces Solutions › Codeforces Round 165 (Div. 2) ›

CF 270B - Multithreading

CF 270B - Multithreading Rating: 1400 Tags: data structures, greedy, implementation Solve time: 2m 19s Verified: yes Solution Problem Understanding The forum keeps a list of threads ordered by the time of their latest message. Whenever someone posts in a thread, that thread immediately moves to the front of the list. No other reordering happens. Initially the threads are ordered as 1, 2, 3, ..., n . After some unknown...

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Codeforces Round 254 (Div. 2)

Codeforces Round 254 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 1200-1200 | Time: 1m 21s Problem Name Rating Tags Solve Time Verified A DZY Loves Chessboard 1200 dfs-and-similar, implementation 1m 21s ✓

Practice › Codeforces Solutions › Codeforces Round 112 (Div. 2) ›

CF 165A - Supercentral Point

CF 165A - Supercentral Point Rating: 1000 Tags: implementation Solve time: 1m 52s Verified: no Solution Problem Understanding We are given a set of points on a 2D Cartesian plane. A point is called supercentral if there exists at least one other point directly to its left, one directly to its right, one directly above it, and one directly below it. The key detail is that these neighbors must share...

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Codeforces Round 149 (Div. 2)

Codeforces Round 149 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 1100-2100 | Time: 12m 58s Problem Name Rating Tags Solve Time Verified A Heads or Tails 1100 brute-force, implementation 3m 26s ✓ B Big Segment 1100 implementation, sortings 1m 12s ✓ C King's Path 1800 dfs-and-similar, graphs, hashing 3m 11s ✗ D Dispute 2100 dfs-and-similar, graphs, greedy 1m 37s ✗ E XOR on...

Practice › Codeforces Solutions › CROC-MBTU 2012, Elimination Round (ACM-ICPC) ›

CF 245E - Mishap in Club

CF 245E - Mishap in Club Rating: 1400 Tags: greedy, implementation Solve time: 1m 24s Verified: yes Solution Problem Understanding We are given a chronological log of a single night in a club. Every character in the input string represents one event: a “+” means someone entered the club, and a “-” means someone left. We do not know how many people were initially inside before the log started, and...

Practice › Codeforces Solutions › Codeforces Beta Round 99 (Div. 2) ›

CF 139B - Wallpaper

CF 139B - Wallpaper Rating: 1600 Tags: implementation, math Solve time: 1m 27s Verified: yes Solution Problem Understanding We are asked to compute the minimum cost to paper all walls in an apartment where each room is a rectangular prism. For each room, the length, width, and height are given. The perimeter of a room determines how many strips of wallpaper are needed. Each type of wallpaper comes in rolls...

Practice › Codeforces Solutions › Codeforces Round 184 (Div. 2) ›

CF 305A - Strange Addition

CF 305A - Strange Addition Rating: 1600 Tags: brute force, constructive algorithms, implementation Solve time: 1m 22s Verified: yes Solution Problem Understanding We are asked to select the largest possible subset of integers from a given set such that any two numbers in the subset can be summed by Vasya. Vasya’s summing rule is unusual: for each decimal place, at least one of the two numbers must have a zero...

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Codeforces Round 155 (Div. 2)

Codeforces Round 155 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 2/5 | Rating range: 1200-2300 | Time: 37m 47s Problem Name Rating Tags Solve Time Verified A Cards with Numbers 1200 constructive-algorithms, sortings 2m 30s ✗ B Jury Size 1500 brute-force, implementation 14m 52s ✓ C Anagram 1800 greedy, strings 14m 52s ✓ D Rats 2300 brute-force, dfs-and-similar, graphs 3m 1s ✗ E Dormitory 2100 dp, implementation...

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Codeforces Round 237 (Div. 2)

Codeforces Round 237 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 0/4 | Rating range: 1000-1900 | Time: 12m 42s Problem Name Rating Tags Solve Time Verified A Valera and X 1000 implementation 4m 55s ✗ B Marathon 1500 implementation, math 2m 40s ✗ C Restore Graph 1800 dfs-and-similar, graphs, sortings 3m 31s ✗ D Minesweeper 1D 1900 dp, implementation 1m 36s ✗

Practice › Codeforces Solutions › Codeforces Round 241 (Div. 2) ›

CF 416B - Art Union

CF 416B - Art Union Rating: 1300 Tags: brute force, dp, implementation Solve time: 1m 26s Verified: yes Solution Problem Understanding We are given a production line where multiple paintings move through a fixed sequence of painters. Every painting must pass through all painters in order, from the first to the last. Each painter processes pictures sequentially in their own queue, and they cannot work on more than one picture...

Practice › Codeforces Solutions › Codeforces Round 132 (Div. 2) ›

CF 215C - Crosses

CF 215C - Crosses Rating: 2100 Tags: brute force, implementation Solve time: 1m 39s Verified: yes Solution Problem Understanding Each cross is defined by two axis-aligned rectangles centered at the same cell (x0, y0) . The first rectangle extends a cells vertically and b cells horizontally from the center, so its size is: $(2a+1)(2b+1)$ The second rectangle is defined similarly using c and d . A cell belongs to the...

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Codeforces Round 175 (Div. 2)

Codeforces Round 175 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1200-2600 | Time: 1m 58s Problem Name Rating Tags Solve Time Verified B Find Marble 1200 implementation 58s ✓ E Positions in Permutations 2600 combinatorics, dp, math 1m ✓

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Codeforces Round 177 (Div. 1)

Codeforces Round 177 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 1/2 | Rating range: 1700-2400 | Time: 3m 45s Problem Name Rating Tags Solve Time Verified C Polo the Penguin and XOR operation 1700 implementation, math 1m 39s ✗ D Polo the Penguin and Trees 2400 combinatorics, dfs-and-similar, trees 2m 6s ✓

Practice › Codeforces Solutions › Codeforces Round 158 (Div. 2) ›

CF 260B - Ancient Prophesy

CF 260B - Ancient Prophesy Rating: 1600 Tags: brute force, implementation, strings Solve time: 2m 12s Verified: yes Solution Problem Understanding The input is a long string made only of digits and hyphens. Somewhere inside this string, there may be many substrings that look like dates written in the exact format dd-mm-yyyy . We must find which valid date appears most often as a substring. A valid date must satisfy...

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Codeforces Round 183 (Div. 1)

Codeforces Round 183 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1300-3000 | Time: 15m 59s Problem Name Rating Tags Solve Time Verified A Lucky Permutation Triple 1300 constructive-algorithms, implementation, math 2m 15s ✗ B Rectangle Puzzle II 1700 implementation, math 3m 45s ✓ C Minimum Modular 2400 brute-force, graphs, math 4m 56s ✓ D Rotatable Number 2600 math, number-theory 1m 56s ✓ E...

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Codeforces Round 101 (Div. 2)

Codeforces Round 101 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 800-2300 | Time: 10m 27s Problem Name Rating Tags Solve Time Verified A Amusing Joke 800 implementation, sortings, strings 1m 31s ✓ B Hopscotch 1400 geometry, math 1m 26s ✓ C Queue 1800 constructive-algorithms, greedy, sortings 2m 24s ✗ D Take-off Ramps 2300 graphs, shortest-paths 2m 15s ✓ E Clearing Up 2300 constructive-algorithms,...

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VK Cup 2012 Qualification Round 1

VK Cup 2012 Qualification Round 1 Type: Special | Problems: 5 | Verified: 5/5 | Rating range: 800-1900 | Time: 7m 26s Problem Name Rating Tags Solve Time Verified A Next Round 800 *special, implementation 1m 29s ✓ B Taxi 1100 *special, greedy, implementation 1m 21s ✓ C Cd and pwd commands 1400 *special, data-structures, implementation 1m 45s ✓ D Ice Sculptures 1300 *special, brute-force, number-theory 1m 38s ✓ E...

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Codeforces Round 130 (Div. 2)

Codeforces Round 130 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 4/4 | Rating range: 900-2100 | Time: 4m 49s Problem Name Rating Tags Solve Time Verified A Dubstep 900 strings 59s ✓ C Police Station 1900 dp, graphs, shortest-paths 1m 18s ✓ D Prizes, Prizes, more Prizes 1200 implementation 1m 26s ✓ E Blood Cousins 2100 binary-search, data-structures, dfs-and-similar 1m 6s ✓

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Codeforces Round 169 (Div. 2)

Codeforces Round 169 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 2/3 | Rating range: 900-1700 | Time: 4m 36s Problem Name Rating Tags Solve Time Verified A Lunch Rush 900 implementation 1m 30s ✗ C Little Girl and Maximum Sum 1500 data-structures, greedy, implementation 1m 42s ✓ D Little Girl and Maximum XOR 1700 bitmasks, dp, greedy 1m 24s ✓

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Codeforces Round 238 (Div. 1)

Codeforces Round 238 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 0/2 | Rating range: 2200-2800 | Time: 6m 36s Problem Name Rating Tags Solve Time Verified D Hill Climbing 2200 dfs-and-similar, geometry, trees 2m 13s ✗ E Hamming Triples 2800 implementation, math, two-pointers 4m 23s ✗

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Codeforces Round 243 (Div. 2)

Codeforces Round 243 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1300 | Time: 2m 57s Problem Name Rating Tags Solve Time Verified A Sereja and Mugs 800 implementation 1m 20s ✓ B Sereja and Mirroring 1300 implementation 1m 37s ✓

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Croc Champ 2013 - Qualification Round

Croc Champ 2013 - Qualification Round Type: Special | Problems: 2 | Verified: 2/2 | Rating range: 1300-2000 | Time: 3m 17s Problem Name Rating Tags Solve Time Verified B Command Line Arguments 1300 *special, implementation, strings 1m 26s ✓ E Tree-String Problem 2000 *special, dfs-and-similar, hashing 1m 51s ✓

Practice › Codeforces Solutions › Codeforces Round 178 (Div. 2) ›

CF 294D - Shaass and Painter Robot

CF 294D - Shaass and Painter Robot Rating: 2500 Tags: brute force, implementation, number theory Solve time: 1m 47s Verified: no Solution Problem Understanding We are asked to simulate a painter robot moving diagonally across a rectangular floor made of tiles. Each tile starts white, and the robot paints a tile black whenever it enters it. The robot can face one of four diagonal directions: up-left, up-right, down-left, or down-right....

Practice › Codeforces Solutions › Codeforces Round 240 (Div. 2) ›

CF 415A - Mashmokh and Lights

CF 415A - Mashmokh and Lights Rating: 900 Tags: implementation Solve time: 1m 23s Verified: yes Solution Problem Understanding The factory has a row of lights indexed from left to right. Every light starts in the “on” state. Mashmokh performs a sequence of button presses, and each button has an index that determines how far to the right its effect extends. When a button with index i is pressed, it...

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CF 342A - Xenia and Divisors

CF 342A - Xenia and Divisors Rating: 1200 Tags: greedy, implementation Solve time: 6m 2s Verified: no Solution Problem Understanding We are given a sequence of positive integers, all between 1 and 7, whose length is divisible by three. The task is to split this sequence into triplets so that within each triplet the numbers are strictly increasing and each number divides the next. Each integer must appear in exactly...

Practice › Codeforces Solutions › Codeforces Round 134 (Div. 2) ›

CF 218A - Mountain Scenery

CF 218A - Mountain Scenery Rating: 1100 Tags: brute force, constructive algorithms, implementation Solve time: 2m 49s Verified: no Solution Problem Understanding We are given a polyline representing mountain peaks. The polyline has 2*n + 1 vertices, with even-indexed vertices (2, 4, 6, ..., 2*n) representing peaks. In the initial picture, each peak is strictly higher than its neighbors, i.e., for every even i , y[i-1] < y[i] > y[i+1]...

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Codeforces Round 160 (Div. 2)

Codeforces Round 160 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 0/1 | Rating range: 800-800 | Time: 3m 6s Problem Name Rating Tags Solve Time Verified A Roma and Lucky Numbers 800 implementation 3m 6s ✗

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Codeforces Round 193 (Div. 2)

Codeforces Round 193 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 0/2 | Rating range: 2200-2400 | Time: 9m Problem Name Rating Tags Solve Time Verified C Students' Revenge 2200 data-structures, greedy, sortings 7m 1s ✗ E Binary Key 2400 dp, greedy, implementation 1m 59s ✗

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Codeforces Testing Round 4

Codeforces Testing Round 4 Type: Special | Problems: 2 | Verified: 2/2 | Rating range: 1300-2500 | Time: 2m 45s Problem Name Rating Tags Solve Time Verified A Punctuation 1300 implementation, strings 1m 18s ✓ B Smile House 2500 binary-search, graphs, matrices 1m 27s ✓

Practice › Codeforces Solutions › Codeforces Round 237 (Div. 2) ›

CF 404D - Minesweeper 1D

CF 404D - Minesweeper 1D Rating: 1900 Tags: dp, implementation Solve time: 1m 36s Verified: no Solution Problem Understanding We are given a line of length $n$, where each position can either already contain a bomb, already contain a number, or be undecided. A bomb is fixed as a * . A number cell contains a digit 0, 1, or 2, and its meaning is strict: it must equal the...

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Codeforces Round 153 (Div. 2)

Codeforces Round 153 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 1100-1800 | Time: 3m 28s Problem Name Rating Tags Solve Time Verified A Little Xor 1100 brute-force, implementation 1m 21s ✗ B Unsorting Array 1800 brute-force, sortings 2m 7s ✓

Practice › Codeforces Solutions › Codeforces Round 235 (Div. 2) ›

CF 401A - Vanya and Cards

CF 401A - Vanya and Cards Rating: 800 Tags: implementation, math Solve time: 4m 10s Verified: no Solution Problem Understanding Vanya has discovered a subset of cards from his original infinite collection, where each card carries an integer between -x and x. His goal is to balance the sum of these found cards to zero by potentially adding additional cards from the infinite supply. The task is to determine the...

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Codeforces Round 108 (Div. 2)

Codeforces Round 108 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 900-2600 | Time: 9m 28s Problem Name Rating Tags Solve Time Verified A Marks 900 implementation 1m 8s ✓ B Steps 1300 binary-search, implementation 1m 42s ✓ C Pocket Book 1400 combinatorics 1m 33s ✓ D Frames 2600 brute-force 2m 41s ✗ E Garden 2500 bitmasks, dp, graphs 2m 24s ✓

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CF 159A - Friends or Not

CF 159A - Friends or Not Rating: 1400 Tags: *special, greedy, implementation Solve time: 1m 47s Verified: yes Solution Problem Understanding We are given a chronological log of private messages between users in a social network. Each record contains the sender, the receiver, and the timestamp of the message. Two users become friends if one of them replies to the other's message quickly enough. More precisely, suppose user A sends...

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CF 146B - Lucky Mask

CF 146B - Lucky Mask Rating: 1300 Tags: brute force, implementation Solve time: 1m 30s Verified: yes Solution Problem Understanding We are given two integers. The first number, a , is arbitrary. The second number, b , is guaranteed to be lucky, meaning every digit of b is either 4 or 7 . For any positive integer, its "mask" is formed by taking only the digits 4 and 7 from...

Practice › Codeforces Solutions › Codeforces Round 169 (Div. 2) ›

CF 276A - Lunch Rush

CF 276A - Lunch Rush Rating: 900 Tags: implementation Solve time: 1m 30s Verified: no Solution Problem Understanding The problem describes a lunch scenario where three Rabbits have a fixed break of k time units and a list of n restaurants. Each restaurant is defined by two numbers: the joy fᵢ the Rabbits gain if they finish on time, and the time tᵢ it takes to eat there. If tᵢ...

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Codeforces Round 172 (Div. 2)

Codeforces Round 172 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 800-800 | Time: 1m 15s Problem Name Rating Tags Solve Time Verified A Word Capitalization 800 implementation, strings 1m 15s ✓

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Codeforces Round 140 (Div. 2)

Codeforces Round 140 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1100-1300 | Time: 6m 2s Problem Name Rating Tags Solve Time Verified A Where do I Turn? 1300 geometry 2m 35s ✓ B Effective Approach 1100 implementation 3m 27s ✓

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Codeforces Round 249 (Div. 2)

Codeforces Round 249 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 1000-1000 | Time: 1m 7s Problem Name Rating Tags Solve Time Verified A Queue on Bus Stop 1000 implementation 1m 7s ✓

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Codeforces Round 185 (Div. 1)

Codeforces Round 185 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 3/4 | Rating range: 1300-2500 | Time: 7m 26s Problem Name Rating Tags Solve Time Verified A The Closest Pair 1300 constructive-algorithms, implementation 3m 3s ✓ B Cats Transport 2400 data-structures, dp 56s ✓ C Fetch the Treasure 2500 brute-force, data-structures, graphs 1m 7s ✓ E Biologist 2300 flows 2m 20s ✗

Practice › Codeforces Solutions › Codeforces Round 254 (Div. 2) ›

CF 445A - DZY Loves Chessboard

CF 445A - DZY Loves Chessboard Rating: 1200 Tags: dfs and similar, implementation Solve time: 1m 21s Verified: yes Solution Problem Understanding We are given a chessboard represented as an n by m grid where each cell is either good or bad. A good cell is indicated by a "." and a bad cell by a "-". On every good cell, we must place a chessman that is either white...

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CF 243C - Colorado Potato Beetle

CF 243C - Colorado Potato Beetle Rating: 2200 Tags: dfs and similar, implementation Solve time: 1m 37s Verified: no Solution Problem Understanding We are working on an enormous infinite grid of unit square cells, and we can think of each cell as a “bed” in a potato field. We start in the center cell and walk according to a sequence of axis-aligned moves. Every time we move, we do not...

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CF 306A - Candies

CF 306A - Candies Rating: 800 Tags: implementation Solve time: 3m 20s Verified: no Solution Problem Understanding Polycarpus has a certain number of candies and a number of friends. He wants to distribute all the candies among his friends in such a way that every friend gets a positive number of candies, and the difference between the friend who receives the most candies and the friend who receives the least...

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CF 272C - Dima and Staircase

CF 272C - Dima and Staircase Rating: 1500 Tags: data structures, implementation Solve time: 1m 28s Verified: yes Solution Problem Understanding We have a staircase where the height of stair i is a[i] , and the heights are already sorted in non-decreasing order. Boxes are dropped one after another. A box with width w covers exactly the first w stairs, meaning its horizontal span is above stairs 1..w . The...

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CF 427E - Police Patrol

CF 427E - Police Patrol Rating: 2000 Tags: greedy, implementation, math, ternary search Solve time: 1m 54s Verified: yes Solution Problem Understanding All criminals stand on the x-axis, and we must choose one integer coordinate for the police station. The patrol car starts from the station, visits some criminals, brings them back to the station, then repeats until everyone is arrested. Each trip can carry at most m criminals. The...

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Codeforces Round 117 (Div. 2)

Codeforces Round 117 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1000-2200 | Time: 11m 48s Problem Name Rating Tags Solve Time Verified A Battlefield 2200 geometry, graphs, implementation 3m 47s ✓ B Vasya's Calendar 1000 implementation 3m 18s ✗ C Optimal Sum 2000 data-structures, greedy 1m 50s ✓ D Common Divisors 1400 brute-force, hashing, implementation 1m 36s ✓ E Wooden Fence 1800 dp...

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Codeforces Round 199 (Div. 2)

Codeforces Round 199 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 2/3 | Rating range: 1200-2400 | Time: 16m 31s Problem Name Rating Tags Solve Time Verified A Xenia and Divisors 1200 greedy, implementation 6m 2s ✗ C Cupboard and Balloons 1900 geometry 5m 17s ✓ E Xenia and Tree 2400 data-structures, divide-and-conquer, trees 5m 12s ✓

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Codeforces Round 135 (Div. 2)

Codeforces Round 135 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 3/3 | Rating range: 1000-1600 | Time: 5m 50s Problem Name Rating Tags Solve Time Verified A k-String 1000 implementation, strings 1m 22s ✓ B Special Offer! Super Price 999 Bourles! 1400 implementation 1m 29s ✓ C Color Stripe 1600 brute-force, dp, greedy 2m 59s ✓

Practice › Codeforces Solutions › Codeforces Round 204 (Div. 1) ›

CF 351A - Jeff and Rounding

CF 351A - Jeff and Rounding Rating: 1800 Tags: dp, greedy, implementation, math Solve time: 1m 37s Verified: no Solution Problem Understanding We are given 2 n real numbers representing Jeff's birthday gifts. Jeff dislikes fractional numbers, so he performs n pairwise operations to "adjust" the numbers. In each operation, he selects two distinct numbers that have not been used before, rounds one down to the nearest integer, and rounds...

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Codeforces Round 177 (Div. 2)

Codeforces Round 177 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 1400-1400 | Time: 1m 16s Problem Name Rating Tags Solve Time Verified B Polo the Penguin and Matrix 1400 brute-force, dp, implementation 1m 16s ✓

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CF 177A1 - Good Matrix Elements

CF 177A1 - Good Matrix Elements Rating: 800 Tags: implementation Solve time: 1m 37s Verified: no Solution Problem Understanding We are given a square matrix of size n × n , where n is guaranteed to be an odd number. Each element of the matrix is a non-negative integer. The task is to compute the sum of "good" elements, which are defined as elements that belong to at least one...

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Codeforces Round 132 (Div. 2)

Codeforces Round 132 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 900-2100 | Time: 8m 51s Problem Name Rating Tags Solve Time Verified A Bicycle Chain 900 brute-force, implementation 1m 25s ✓ B Olympic Medal 1300 greedy, math 1m 43s ✓ C Crosses 2100 brute-force, implementation 1m 39s ✓ D Hot Days 1900 greedy 1m 6s ✓ E Periodical Numbers 2100 combinatorics, dp, number-theory...

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CF 192A - Funky Numbers

CF 192A - Funky Numbers Rating: 1300 Tags: binary search, brute force, implementation Solve time: 47s Verified: no Solution Problem-Type Check This is a Type A - “Find all X” problem. A valid proof must do two things: Verify that every claimed solution actually satisfies the conditions. Prove that no other solutions exist. The proposed solution does not complete either direction fully. The only explicit candidate eventually found is $550$,...

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CF 223A - Bracket Sequence

CF 223A - Bracket Sequence Rating: 1700 Tags: data structures, expression parsing, implementation Solve time: 1m 41s Verified: yes Solution Problem Understanding We are given a string consisting only of four bracket characters: ( , ) , [ and ] . The string itself is not guaranteed to be balanced. Our task is to find a contiguous substring that forms a valid bracket sequence. Among all valid substrings, we want...

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CF 305C - Ivan and Powers of Two

CF 305C - Ivan and Powers of Two Rating: 1600 Tags: greedy, implementation Solve time: 1m 48s Verified: yes Solution Problem Understanding We are given a sorted array of exponents. Instead of the exponents themselves, Ivan writes the corresponding powers of two on paper: $$2^{a_1}, 2^{a_2}, \dots, 2^{a_n}$$ We may add more numbers, but every added number must also be a power of two. The goal is to make the...

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CF 409H - A + B Strikes Back

CF 409H - A + B Strikes Back Rating: 1500 Tags: *special, brute force, constructive algorithms, dsu, implementation Solve time: 33s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 146 (Div. 1) ›

CF 235E - Number Challenge

CF 235E - Number Challenge Rating: 2600 Tags: combinatorics, dp, implementation, math, number theory Solve time: 3m 42s Verified: yes Solution Problem Understanding We need to compute $$\sum_{i=1}^{a}\sum_{j=1}^{b}\sum_{k=1}^{c} d(i \cdot j \cdot k)$$ where $d(x)$ is the number of positive divisors of $x$. The three nested loops range over every triple $(i,j,k)$, multiply the numbers together, compute how many divisors that product has, and add everything modulo $2^{30} = 1073741824$....

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Codeforces Round 145 (Div. 2, ACM-ICPC Rules)

Codeforces Round 145 (Div. 2, ACM-ICPC Rules) Type: Div. 2 | Problems: 5 | Verified: 2/5 | Rating range: 1000-2000 | Time: 9m 42s Problem Name Rating Tags Solve Time Verified B Reading 1000 sortings 1m 19s ✓ C Weather 1300 dp, implementation 1m 27s ✓ F Fence 1800 dp 1m 5s ✗ G Practice 1600 constructive-algorithms, divide-and-conquer, implementation 2m 54s ✗ H Merging Two Decks 2000 constructive-algorithms, greedy 2m...

Practice › Codeforces Solutions › Codeforces Round 128 (Div. 2) ›

CF 203A - Two Problems

CF 203A - Two Problems Rating: 1200 Tags: brute force, implementation Solve time: 1m 6s Verified: yes Solution Problem Understanding There are two independent tasks available during a contest that lasts from minute 0 up to minute t minus 1. Each task has a score that decreases linearly with time. If you solve the first task at minute i, you receive a minus i multiplied by da points subtracted from...

Practice › Codeforces Solutions › Codeforces Round 171 (Div. 2) ›

CF 279A - Point on Spiral

CF 279A - Point on Spiral Rating: 1400 Tags: brute force, geometry, implementation Solve time: 1m 28s Verified: yes Solution Problem Understanding The spiral starts at the origin and grows outward by alternating directions: right, up, left, down. Each new segment is longer than the previous pair. The first few moves are: right 1 up 1 left 2 down 2 right 3 up 3 and so on forever. We are...

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Codeforces Round 136 (Div. 2)

Codeforces Round 136 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1300 | Time: 3m 57s Problem Name Rating Tags Solve Time Verified A Little Elephant and Function 1000 implementation, math 1m 10s ✓ B Little Elephant and Numbers 1300 implementation 2m 47s ✓

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Codeforces Round 133 (Div. 2)

Codeforces Round 133 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 1200-2000 | Time: 7m 31s Problem Name Rating Tags Solve Time Verified A Tiling with Hexagons 1200 implementation, math 56s ✓ B Forming Teams 1700 dfs-and-similar, implementation 1m 27s ✓ C Hiring Staff 1800 greedy 2m 5s ✗ D Spider's Web 1700 binary-search, sortings, two-pointers 1m 26s ✗ E Martian Luck 2000 math,...

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Codeforces Round 178 (Div. 2)

Codeforces Round 178 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 3/4 | Rating range: 800-2500 | Time: 6m 7s Problem Name Rating Tags Solve Time Verified A Shaass and Oskols 800 implementation, math 1m 38s ✓ C Shaass and Lights 1900 combinatorics, number-theory 1m 10s ✓ D Shaass and Painter Robot 2500 brute-force, implementation, number-theory 1m 47s ✗ E Shaass the Great 2300 dp, trees 1m 32s...

Practice › Codeforces Solutions › Codeforces Round 104 (Div. 1) ›

CF 145D - Lucky Pair

CF 145D - Lucky Pair Rating: 2900 Tags: combinatorics, data structures, implementation Solve time: 1m 48s Verified: no Solution Problem Understanding We are given an array of integers, and some of these integers are "lucky numbers," meaning they consist only of the digits 4 and 7. We are asked to count the number of pairs of non-overlapping contiguous subarrays $[l_1, r_1]$ and $[l_2, r_2]$ such that no lucky number appears...

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CF 174B - File List

CF 174B - File List Rating: 1400 Tags: dp, greedy, implementation Solve time: 3m 40s Verified: yes Solution Problem Understanding We are given one long string that originally consisted of several file names written back to back with no separators. Every valid file name must look like name.ext . The rules are strict. The part before the dot contains only lowercase letters and has length from 1 to 8. The...

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CF 147A - Punctuation

CF 147A - Punctuation Rating: 1300 Tags: implementation, strings Solve time: 1m 18s Verified: yes Solution Problem Understanding We are given a string containing lowercase letters, spaces, and a limited set of punctuation marks: comma, dot, exclamation mark, and question mark. Our goal is to reformat this string so that words are separated by exactly one space, no spaces appear before punctuation, and each punctuation mark is followed by exactly...

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CF 420B - Online Meeting

CF 420B - Online Meeting Rating: 1800 Tags: implementation Solve time: 2m 4s Verified: no Solution Problem Understanding We have a meeting log for a team of developers where each log entry records either a user logging in or logging out. The log may start or end in the middle of the meeting, so we do not know who was online before the first recorded message. Our goal is to...

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CF 188F - Binary Notation

CF 188F - Binary Notation Rating: 1400 Tags: *special, implementation Solve time: 1m 32s Verified: yes Solution Problem Understanding We are given a single positive integer and must print its representation in base 2. In other words, instead of writing the number using decimal digits from 0 to 9, we must write it using only binary digits, 0 and 1. For example, the decimal number 5 becomes 101 in binary...

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Codeforces Round 159 (Div. 2)

Codeforces Round 159 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 4/4 | Rating range: 1100-1900 | Time: 6m 19s Problem Name Rating Tags Solve Time Verified A Sockets 1100 greedy, implementation, sortings 1m 10s ✓ B Playing Cubes 1300 games, greedy, implementation 1m 23s ✓ C View Angle 1800 brute-force, geometry, math 2m 43s ✓ D Sum 1900 greedy, math 1m 3s ✓

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Codeforces Beta Round 99 (Div. 1)

Codeforces Beta Round 99 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1600-2900 | Time: 9m 53s Problem Name Rating Tags Solve Time Verified A Literature Lesson 1600 implementation 2m ✓ B Digits Permutations 1900 greedy 2m 29s ✗ C Mushroom Gnomes - 2 2200 binary-search, data-structures, probabilities 2m ✓ D World of Darkraft 2500 dp, games 2m 6s ✓ E Hellish Constraints 2900...

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Codeforces Round 140 (Div. 1)

Codeforces Round 140 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1400-2900 | Time: 14m 33s Problem Name Rating Tags Solve Time Verified A Flying Saucer Segments 1400 math 5m 43s ✓ B Naughty Stone Piles 1900 greedy 2m 22s ✓ C Anniversary 2400 data-structures, implementation, math 2m 19s ✓ D The table 2100 constructive-algorithms, greedy 2m 58s ✗ E Noble Knight's Path 2900...

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Codeforces Round 252 (Div. 2)

Codeforces Round 252 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 1/3 | Rating range: 1000-2400 | Time: 4m 27s Problem Name Rating Tags Solve Time Verified A Valera and Antique Items 1000 implementation 1m 21s ✓ D Valera and Swaps 2100 constructive-algorithms, dsu, graphs 1m 26s ✗ E Valera and Number 2400 bitmasks, dp, math 1m 40s ✗

Practice › Codeforces Solutions › Codeforces Round 193 (Div. 2) ›

CF 332E - Binary Key

CF 332E - Binary Key Rating: 2400 Tags: dp, greedy, implementation Solve time: 1m 59s Verified: no Solution Problem Understanding We are given a container string p and a target message string s . The container is arbitrary, while the message contains the sequence we wish to extract. The extraction mechanism is governed by a binary key q of length k . The extraction proceeds sequentially through p and q...

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Codeforces Round 239 (Div. 1)

Codeforces Round 239 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 0/4 | Rating range: 1600-3100 | Time: 10m 34s Problem Name Rating Tags Solve Time Verified B Long Path 1600 dp, implementation 1m 3s ✗ C Curious Array 2500 brute-force, combinatorics, implementation 34s ✗ D Largest Submatrix 3 2700 dp, hashing 4m 21s ✗ E k-d-sequence 3100 data-structures 4m 36s ✗

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VK Cup 2012 Finals (unofficial online-version)

VK Cup 2012 Finals (unofficial online-version) Type: Special | Problems: 5 | Verified: 1/5 | Rating range: 1500-3000 | Time: 9m 48s Problem Name Rating Tags Solve Time Verified A Privatization 3000 flows, graphs 2m 20s ✗ B Polycarpus is Looking for Good Substrings 2300 bitmasks, hashing, implementation 1m 54s ✓ C Cowboys 2100 combinatorics, dp, math 1m 28s ✗ D Cutting a Fence 2500 binary-search, data-structures, dsu 1m 8s...

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Codeforces Round 148 (Div. 2)

Codeforces Round 148 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 1200-1500 | Time: 4m 55s Problem Name Rating Tags Solve Time Verified A Two Bags of Potatoes 1200 greedy, implementation, math 1m 23s ✓ B Easy Tape Programming 1500 brute-force, implementation 3m 32s ✗

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Codeforces Round 162 (Div. 1)

Codeforces Round 162 (Div. 1) Type: Div. 1 | Problems: 1 | Verified: 1/1 | Rating range: 1200-1200 | Time: 1m 5s Problem Name Rating Tags Solve Time Verified A Escape from Stones 1200 constructive-algorithms, data-structures, implementation 1m 5s ✓

Practice › Codeforces Solutions › Coder-Strike 2014 - Finals (online edition, Div. 1) ›

CF 420C - Bug in Code

CF 420C - Bug in Code Rating: 1900 Tags: data structures, graphs, implementation, two pointers Solve time: 1m 57s Verified: yes Solution Problem Understanding Each participant in the company meeting points to two other people and claims that the culprit is one of those two. From this we can think of the input as an array of length $n$, where each index $i$ stores an unordered pair $(x_i, y_i)$. This...

Practice › Codeforces Solutions › Codeforces Round 162 (Div. 2) ›

CF 265A - Colorful Stones (Simplified Edition)

CF 265A - Colorful Stones (Simplified Edition) Rating: 800 Tags: implementation Solve time: 1m 17s Verified: no Solution Problem Understanding The problem describes a row of stones, each colored red, green, or blue, represented by a string s of characters 'R', 'G', and 'B'. Squirrel Liss starts on the first stone and executes a sequence of color-based instructions, given by a second string t . Each instruction corresponds to a...

Practice › Codeforces Solutions › VK Cup 2012 Wild-card Round 1 ›

CF 162A - Pentagonal numbers

CF 162A - Pentagonal numbers Rating: 1100 Tags: *special, implementation Solve time: 3m 10s Verified: yes Solution Problem Understanding We need to compute the n -th pentagonal number. Pentagonal numbers form a sequence generated by a direct mathematical formula: $$P_n = \frac{3n^2 - n}{2}$$ The input contains a single integer n , and the output is the value of this formula for that position in the sequence. The constraints are...

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Codeforces Round 136 (Div. 1)

Codeforces Round 136 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 3/4 | Rating range: 1300-2500 | Time: 8m 14s Problem Name Rating Tags Solve Time Verified A Little Elephant and Problem 1300 implementation, sortings 2m 48s ✓ B Little Elephant and Array 1800 constructive-algorithms, data-structures 1m 7s ✓ C Little Elephant and Shifts 2100 data-structures 1m 54s ✓ D Little Elephant and Triangle 2500 geometry, math 2m...

Practice › Codeforces Solutions › Codeforces Round 204 (Div. 2) ›

CF 352B - Jeff and Periods

CF 352B - Jeff and Periods Rating: 1300 Tags: implementation, sortings Solve time: 1m 25s Verified: yes Solution Problem Understanding We are given a sequence of integers, and for each distinct value we want to understand how its occurrences are spaced across the array. For any value $x$, we look at all indices where $x$ appears. If those indices form a sequence with a constant difference, then $x$ is considered...

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ABBYY Cup 3.0 - Finals (online version)

ABBYY Cup 3.0 - Finals (online version) Type: Special | Problems: 7 | Verified: 3/7 | Rating range: 1100-2900 | Time: 27m 55s Problem Name Rating Tags Solve Time Verified B1 Shave Beaver! 1700 implementation 2m 32s ✓ C1 The Great Julya Calendar 1100 dp 4m 55s ✓ C2 The Great Julya Calendar 2400 dp 5m 52s ✗ C3 The Great Julya Calendar 2500 dp 1m 53s ✓ D1 Escaping...

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Codeforces Round 162 (Div. 2)

Codeforces Round 162 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 800-1000 | Time: 2m 41s Problem Name Rating Tags Solve Time Verified A Colorful Stones (Simplified Edition) 800 implementation 1m 17s ✗ B Roadside Trees (Simplified Edition) 1000 greedy, implementation 1m 24s ✓

Practice › Codeforces Solutions › Codeforces Round 203 (Div. 2) ›

CF 350C - Bombs

CF 350C - Bombs Rating: 1600 Tags: greedy, implementation, sortings Solve time: 3m 48s Verified: yes Solution Problem Understanding We have a robot starting at the origin on a 2D grid. Several bombs are placed at distinct coordinates, and the robot must destroy all of them. The robot can move horizontally or vertically, pick up a bomb when standing on its cell, and destroy a carried bomb only after returning...

Practice › Codeforces Solutions › Codeforces Round 177 (Div. 2) ›

CF 289B - Polo the Penguin and Matrix

CF 289B - Polo the Penguin and Matrix Rating: 1400 Tags: brute force, dp, implementation, sortings, ternary search Solve time: 1m 16s Verified: yes Solution Problem Understanding We are given a matrix of integers and a number d . The penguin can either add or subtract d from any matrix element in a single move. The goal is to make all elements equal using the fewest moves possible. The output...

Practice › Codeforces Solutions › Codeforces Round 238 (Div. 1) ›

CF 406E - Hamming Triples

CF 406E - Hamming Triples Rating: 2800 Tags: implementation, math, two pointers Solve time: 4m 23s Verified: no Solution Problem Understanding The problem presents a collection of binary strings of a fixed length, but rather than giving the strings explicitly, each string is described compactly: the first $f_i$ bits are the same, $s_i$, and the remaining $n-f_i$ bits are the opposite of $s_i$. Each string is therefore strictly increasing or...

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Codeforces Round 185 (Div. 2)

Codeforces Round 185 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 0/1 | Rating range: 1100-1100 | Time: 3m 13s Problem Name Rating Tags Solve Time Verified A Whose sentence is it? 1100 implementation, strings 3m 13s ✗

Practice › Codeforces Solutions › Codeforces Round 140 (Div. 2) ›

CF 227B - Effective Approach

CF 227B - Effective Approach Rating: 1100 Tags: implementation Solve time: 3m 27s Verified: yes Solution Problem Understanding We are given a permutation of integers from 1 to n and a list of queries asking for the positions of specific elements. The task is to compare two linear search strategies. Vasya's strategy starts searching from the first element of the array toward the last, while Petya's strategy searches from the...

Practice › Codeforces Solutions › Coder-Strike 2014 - Round 2 ›

CF 413B - Spyke Chatting

CF 413B - Spyke Chatting Rating: 1300 Tags: implementation Solve time: 1m 48s Verified: no Solution Problem Understanding We are given a company where employees participate in several independent chat groups. Each chat has a fixed membership defined in advance. Over time, a log records messages: each event says that a particular employee posts in a particular chat. The key rule is simple but asymmetric: when someone sends a message...

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Codeforces Round 238 (Div. 2)

Codeforces Round 238 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 0/4 | Rating range: 900-2300 | Time: 15m 46s Problem Name Rating Tags Solve Time Verified A Gravity Flip 900 greedy, implementation, sortings 6m 21s ✗ B Domino Effect 1100 - 1m 23s ✗ C Unusual Product 1600 implementation, math 1m 27s ✗ E Graph Cutting 2300 dfs-and-similar, graphs 6m 35s ✗

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Codeforces Round 122 (Div. 2)

Codeforces Round 122 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 900-1200 | Time: 2m 59s Problem Name Rating Tags Solve Time Verified A Exams 900 implementation, math 1m 28s ✓ B Square 1200 math 1m 31s ✓

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Codeforces Round 167 (Div. 2)

Codeforces Round 167 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 2/3 | Rating range: 1400-2200 | Time: 5m 30s Problem Name Rating Tags Solve Time Verified B Dima and Sequence 1400 implementation, math 1m 30s ✓ C Dima and Staircase 1500 data-structures, implementation 1m 28s ✓ E Dima and Horses 2200 combinatorics, constructive-algorithms, graphs 2m 32s ✗

Practice › Codeforces Solutions › Codeforces Round 177 (Div. 1) ›

CF 288C - Polo the Penguin and XOR operation

CF 288C - Polo the Penguin and XOR operation Rating: 1700 Tags: implementation, math Solve time: 1m 39s Verified: no Solution Problem Understanding We are given all integers from 0 to n, and we must arrange them into a permutation p. Each position i contributes a value equal to i XOR p[i], and the goal is to maximize the total sum of these contributions over all positions. So we are...

Practice › Codeforces Solutions › Codeforces Round 239 (Div. 1) ›

CF 407B - Long Path

CF 407B - Long Path Rating: 1600 Tags: dp, implementation Solve time: 1m 3s Verified: no Solution

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Codeforces Round 125 (Div. 1)

Codeforces Round 125 (Div. 1) Type: Div. 1 | Problems: 3 | Verified: 1/3 | Rating range: 1700-2700 | Time: 6m 48s Problem Name Rating Tags Solve Time Verified A About Bacteria 1700 implementation, math 1m 28s ✓ D Cube Snake 2700 constructive-algorithms 2m 13s ✗ E Gripping Story 2400 binary-search, data-structures, sortings 3m 7s ✗

Practice › Codeforces Solutions › Codeforces Round 116 (Div. 2, ACM-ICPC Rules) ›

CF 180A - Defragmentation

CF 180A - Defragmentation Rating: 1800 Tags: implementation Solve time: 1m 20s Verified: yes Solution Problem Understanding We are tasked with reorganizing a hard disk so that files occupy contiguous clusters from the beginning of the disk, and free clusters are pushed to the end. The disk has n clusters, numbered from 1 to n , and m files. Each file is described by a sequence of cluster numbers where...

Practice › Codeforces Solutions › Coder-Strike 2014 - Round 2 ›

CF 413A - Data Recovery

CF 413A - Data Recovery Rating: 1200 Tags: implementation Solve time: 1m 42s Verified: yes Solution Problem Understanding The problem gives us a sequence of processor temperatures recorded over n steps. The chief engineer has reliable notes of the minimum and maximum temperature observed, but the assistant only recorded m of the n temperatures. We are asked to determine whether the reported m temperatures can be extended with additional values...

Practice › Codeforces Solutions › Codeforces Round 150 (Div. 2) ›

CF 244A - Dividing Orange

CF 244A - Dividing Orange Rating: 900 Tags: implementation Solve time: 3m 13s Verified: no Solution Problem Understanding We are asked to divide an orange consisting of n*k segments among k children so that each child receives exactly n segments, each child definitely receives the segment they chose, and no segment is given to more than one child. The input provides the total number of segments per child n ,...

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Codeforces Round 184 (Div. 2)

Codeforces Round 184 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1600-2300 | Time: 7m 58s Problem Name Rating Tags Solve Time Verified A Strange Addition 1600 brute-force, constructive-algorithms, implementation 1m 22s ✓ B Continued Fractions 1700 brute-force, implementation, math 1m 25s ✓ C Ivan and Powers of Two 1600 greedy, implementation 1m 48s ✓ D Olya and Graph 2200 combinatorics, math 1m 36s...

Practice › Codeforces Solutions › Codeforces Round 158 (Div. 2) ›

CF 260A - Adding Digits

CF 260A - Adding Digits Rating: 1400 Tags: implementation, math Solve time: 1m 21s Verified: no Solution Problem Understanding We are given a number a and a target divisor b , along with a count n representing how many digits we want to append to a . Each operation consists of appending a single digit to the right of the current number such that the new number is divisible by...

Practice › Codeforces Solutions › Codeforces Round 155 (Div. 2) ›

CF 254D - Rats

CF 254D - Rats Rating: 2300 Tags: brute force, dfs and similar, graphs, implementation, shortest paths Solve time: 3m 1s Verified: no Solution Problem Understanding The problem presents a rectangular basement of a store as an n × m grid, where some cells are walls, some are empty, and some contain sleeping rats. Vasily has two grenades, and when a grenade explodes in a cell, its blast propagates outward to...

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Codeforces Round 244 (Div. 2)

Codeforces Round 244 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2200 | Time: 7m 50s Problem Name Rating Tags Solve Time Verified A Police Recruits 800 implementation 1m 22s ✓ B Prison Transfer 1100 data-structures, implementation 1m 33s ✓ C Checkposts 1700 dfs-and-similar, graphs, two-pointers 1m 34s ✓ D Match & Catch 2200 dp, string-suffix-structures, strings 1m 27s ✓ E Police Patrol 2000...

Practice › Codeforces Solutions › Codeforces Round 195 (Div. 2) ›

CF 336E - Vasily the Bear and Painting Square

CF 336E - Vasily the Bear and Painting Square Rating: 2700 Tags: bitmasks, combinatorics, dp, implementation Solve time: 3m 22s Verified: yes Solution Problem Understanding Vasily the Bear is creating a geometric structure on the plane using a sequence of squares and line segments, all centered at the origin. The parameter n controls the number of nested squares he draws, each forming vertices at multiples of 2_i_ and 2_i_+1 along...

Practice › Codeforces Solutions › April Fools Day Contest ›

CF 171C - A Piece of Cake

CF 171C - A Piece of Cake Rating: 2000 Tags: *special, implementation Solve time: 1m 30s Verified: yes Solution Problem Understanding The input is a sequence of integers. The first number tells us how many additional integers follow. If the sequence is: 4 1 2 3 4 then there are four values: 1, 2, 3, 4 . The task itself is intentionally disguised by the strange statement. The actual operation...

Practice › Codeforces Solutions › Codeforces Round 191 (Div. 2) ›

CF 327A - Flipping Game

CF 327A - Flipping Game Rating: 1200 Tags: brute force, dp, implementation Solve time: 4m 3s Verified: yes Solution Problem Understanding We are given a short binary array, where each position is either 0 or 1. We are allowed to choose exactly one contiguous segment and invert every value inside it, turning 0 into 1 and 1 into 0. After performing this single operation, we want the resulting array to...

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Coder-Strike 2014 - Finals (online edition, Div. 2)

Coder-Strike 2014 - Finals (online edition, Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1900 | Time: 2m 37s Problem Name Rating Tags Solve Time Verified A Pasha and Hamsters 800 constructive-algorithms, implementation 1m ✓ D Bug in Code 1900 binary-search, data-structures, sortings 1m 37s ✓

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Codeforces Round 191 (Div. 2)

Codeforces Round 191 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 2/3 | Rating range: 1200-2300 | Time: 7m 2s Problem Name Rating Tags Solve Time Verified A Flipping Game 1200 brute-force, dp, implementation 4m 3s ✓ D Block Tower 1900 constructive-algorithms, dfs-and-similar, graphs 1m 34s ✗ E Axis Walking 2300 bitmasks, combinatorics, constructive-algorithms 1m 25s ✓

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Codeforces Round 241 (Div. 2)

Codeforces Round 241 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1300-2500 | Time: 8m 12s Problem Name Rating Tags Solve Time Verified A Guess a number! 1400 greedy, implementation, two-pointers 1m 47s ✗ B Art Union 1300 brute-force, dp, implementation 1m 26s ✓ C Booking System 1600 binary-search, dp, greedy 1m 32s ✓ D Population Size 2400 greedy, implementation, math 1m 23s ✓...

Practice › Codeforces Solutions › Surprise Language Round 6 ›

CF 188C - LCM

CF 188C - LCM Rating: 1400 Tags: *special, implementation, math Solve time: 1m 59s Verified: yes Solution Problem Understanding We are given two positive integers and need to compute their least common multiple. The least common multiple, usually abbreviated as LCM, is the smallest positive integer that both numbers divide evenly. For example, if the numbers are 10 and 42, the answer is 210 because 210 is divisible by both...

Practice › Codeforces Solutions › Codeforces Round 126 (Div. 2) ›

CF 200C - Football Championship

CF 200C - Football Championship Rating: 1800 Tags: brute force, implementation Solve time: 3m 43s Verified: yes Solution Problem Understanding We have a four-team football group where every pair of teams plays exactly once, so the full tournament contains six matches. Five results are already known, and the only remaining match is the one involving BERLAND . Each match contributes points in the usual way. A win gives 3 points,...

Practice › Codeforces Solutions › Codeforces Round 129 (Div. 2) ›

CF 205A - Little Elephant and Rozdil

CF 205A - Little Elephant and Rozdil Rating: 900 Tags: brute force, implementation Solve time: 54s Verified: yes Solution Problem Understanding We are given a list of travel times from the town Rozdil to each of n other towns. Each town has a positive integer time, and the towns are numbered from 1 to n . The goal is to find which town has the smallest travel time. If there...

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VK Cup 2012 Round 3 (Unofficial Div. 2 Edition)

VK Cup 2012 Round 3 (Unofficial Div. 2 Edition) Type: Div. 2 | Problems: 3 | Verified: 3/3 | Rating range: 1100-1800 | Time: 6m 56s Problem Name Rating Tags Solve Time Verified A Problem About Equation 1100 math 1m 33s ✓ B File List 1400 dp, greedy, implementation 3m 40s ✓ C Range Increments 1800 data-structures, greedy 1m 43s ✓

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Codeforces Round 152 (Div. 2)

Codeforces Round 152 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 800-2600 | Time: 11m 52s Problem Name Rating Tags Solve Time Verified A Cupboards 800 implementation 1m 34s ✓ B Chilly Willy 1400 math, number-theory 2m 53s ✓ C Robo-Footballer 2000 binary-search, geometry 2m ✗ D Sweets for Everyone! 2300 binary-search, greedy, implementation 3m 8s ✓ E Piglet's Birthday 2600 dp, math, probabilities...

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Codeforces Round 204 (Div. 2)

Codeforces Round 204 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1300 | Time: 3m 51s Problem Name Rating Tags Solve Time Verified A Jeff and Digits 1000 brute-force, implementation, math 2m 26s ✓ B Jeff and Periods 1300 implementation, sortings 1m 25s ✓

Practice › Codeforces Solutions › Testing Round 8 ›

CF 328A - IQ Test

CF 328A - IQ Test Rating: 1800 Tags: implementation Solve time: 1m 11s Verified: no Solution Problem Understanding We are given exactly four integers in a sequence, each between 1 and 1000. The goal is to determine whether this sequence forms an arithmetic progression or a geometric progression. If it does, we must compute the next element of the progression. If the sequence fits neither pattern, or if the next...

Practice › Codeforces Solutions › Codeforces Round 183 (Div. 1) ›

CF 303B - Rectangle Puzzle II

CF 303B - Rectangle Puzzle II Rating: 1700 Tags: implementation, math Solve time: 3m 45s Verified: yes Solution Problem Understanding We have a grid-aligned rectangle of size n × m . Every valid point has integer coordinates between (0, 0) and (n, m) . We must choose another axis-aligned rectangle inside it. The rectangle is described by four integers (x1, y1, x2, y2) . The chosen rectangle must satisfy three...

Practice › Codeforces Solutions › Codeforces Round #FF (Div. 2) ›

CF 447B - DZY Loves Strings

CF 447B - DZY Loves Strings Rating: 1000 Tags: greedy, implementation Solve time: 1m 11s Verified: yes Solution Problem Understanding We are given a string made of lowercase letters and a way to assign a numerical weight to each letter. The value of a full string is computed by summing, over all positions, the product of the position index (starting from 1) and the weight of the character at that...

Practice › Codeforces Solutions › Codeforces Round 146 (Div. 2) ›

CF 236A - Boy or Girl

CF 236A - Boy or Girl Rating: 800 Tags: brute force, implementation, strings Solve time: 3m 27s Verified: yes Solution Problem Understanding We are given a username consisting only of lowercase English letters. The task is to count how many different characters appear in that username. The decision rule is simple. If the number of distinct characters is even, we print "CHAT WITH HER!" . If the number is odd,...

Practice › Codeforces Solutions › Codeforces Round 133 (Div. 2) ›

CF 216B - Forming Teams

CF 216B - Forming Teams Rating: 1700 Tags: dfs and similar, implementation Solve time: 1m 27s Verified: yes Solution Problem Understanding We can model the students as an undirected graph. Each student is a vertex, and every pair of enemies creates an edge. We want to split the remaining students into two teams of equal size such that no edge stays inside one team. In graph terms, we need a...

Practice › Codeforces Solutions › Codeforces Round 115 ›

CF 175C - Geometry Horse

CF 175C - Geometry Horse Rating: 1600 Tags: greedy, implementation, sortings, two pointers Solve time: 1m 21s Verified: yes Solution Problem Understanding We are asked to maximize Vasya's score in a game where destroying geometric figures earns points based on a per-figure cost and a global factor. Each figure type has a quantity and a point value. The factor starts at 1 and increases at specific thresholds after a certain...

Practice › Codeforces Solutions › Codeforces Round 161 (Div. 2) ›

CF 263C - Circle of Numbers

CF 263C - Circle of Numbers Rating: 2000 Tags: brute force, dfs and similar, implementation Solve time: 1m 10s Verified: yes Solution Problem Understanding We are given a hidden cyclic arrangement of the integers from 1 to n placed around a circle. From this arrangement, someone constructed a set of ordered pairs describing connections between values. These connections come from a simple geometric rule: two numbers are connected if they...

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Codeforces Round 116 (Div. 2, ACM-ICPC Rules)

Codeforces Round 116 (Div. 2, ACM-ICPC Rules) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1200-2300 | Time: 8m 3s Problem Name Rating Tags Solve Time Verified A Defragmentation 1800 implementation 1m 20s ✓ B Divisibility Rules 2300 math, number-theory 1m 50s ✓ C Letter 1400 dp 1m 46s ✓ D Name 1900 greedy, strings 1m 39s ✓ F Mathematical Analysis Rocks! 1200 constructive-algorithms, implementation, math...

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Codeforces Round 121 (Div. 2)

Codeforces Round 121 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 0/2 | Rating range: 1100-1300 | Time: 3m 47s Problem Name Rating Tags Solve Time Verified A Funky Numbers 1300 binary-search, brute-force, implementation 47s ✗ B Walking in the Rain 1100 brute-force, implementation 3m ✗

Practice › Codeforces Solutions › Codeforces Round 135 (Div. 2) ›

CF 219A - k-String

CF 219A - k-String Rating: 1000 Tags: implementation, strings Solve time: 1m 22s Verified: yes Solution Problem Understanding We are given a lowercase string and an integer k . We may rearrange the letters however we want. The goal is to build a new string that consists of exactly k identical blocks placed one after another. For example, if k = 3 , then the final string must look like:...

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Codeforces Round 176 (Div. 1)

Codeforces Round 176 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 2/2 | Rating range: 2200-2800 | Time: 2m 31s Problem Name Rating Tags Solve Time Verified B Shifting 2200 implementation 1m 1s ✓ E Ladies' Shop 2800 constructive-algorithms, fft, math 1m 30s ✓

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Codeforces Round 144 (Div. 2)

Codeforces Round 144 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 800-1400 | Time: 2m 15s Problem Name Rating Tags Solve Time Verified A Perfect Permutation 800 implementation, math 1m 26s ✓ B Non-square Equation 1400 binary-search, brute-force, math 49s ✗

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Codeforces Round #FF (Div. 2)

Codeforces Round #FF (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 1000-1000 | Time: 1m 11s Problem Name Rating Tags Solve Time Verified B DZY Loves Strings 1000 greedy, implementation 1m 11s ✓

Practice › Codeforces Solutions › Codeforces Round 182 (Div. 2) ›

CF 302B - Eugeny and Play List

CF 302B - Eugeny and Play List Rating: 1200 Tags: binary search, implementation, two pointers Solve time: 3m 25s Verified: yes Solution Problem Understanding The playlist is built from blocks of repeated songs. Song i has duration t[i] , and Eugeny listens to it c[i] times consecutively before moving to the next song. If a song lasts 4 minutes and is repeated 3 times, that block contributes 12 minutes to...

Practice › Codeforces Solutions › Codeforces Round 247 (Div. 2) ›

CF 431A - Black Square

CF 431A - Black Square Rating: 800 Tags: implementation Solve time: 1m 10s Verified: yes Solution Problem Understanding In "Black Square," Jury must press on one of four vertical strips whenever a black square appears. Each strip has a fixed energy cost, measured in calories, for pressing it. We are given four integers representing the calories consumed when pressing the first through fourth strips. The game's progression is described by...

Practice › Codeforces Solutions › CROC-MBTU 2012, Elimination Round (ACM-ICPC) ›

CF 245B - Internet Address

CF 245B - Internet Address Rating: 1100 Tags: implementation, strings Solve time: 1m 53s Verified: yes Solution Problem Understanding Vasya scribbled an Internet address in his notebook, but he was in a hurry and omitted all punctuation characters like : , / , and . . The original address followed the conventional structure of a URL: it had a protocol ( http or ftp ), a domain name consisting of...

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Codeforces Round 111 (Div. 2)

Codeforces Round 111 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 900-2400 | Time: 8m 5s Problem Name Rating Tags Solve Time Verified A Twins 900 greedy, sortings 1m 15s ✓ B Unlucky Ticket 1100 greedy, sortings 1m 29s ✓ C Find Pair 1700 implementation, math, sortings 1m 47s ✓ D Edges in MST 2300 dfs-and-similar, dsu, graphs 1m 21s ✓ E Buses and...

Practice › Codeforces Solutions › Codeforces Round 235 (Div. 2) ›

CF 401B - Sereja and Contests

CF 401B - Sereja and Contests Rating: 1200 Tags: greedy, implementation, math Solve time: 1m 24s Verified: yes Solution Problem Understanding The contest platform numbers every round consecutively by start time. A round can either be a standalone Div2 round, or a pair of simultaneous rounds where Div2 gets identifier i and Div1 gets identifier i + 1 . Sereja only participates in Div2 rounds. Right now he is participating...

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Codeforces Round 194 (Div. 1)

Codeforces Round 194 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 1/2 | Rating range: 1600-2100 | Time: 3m 54s Problem Name Rating Tags Solve Time Verified A Secrets 1600 greedy 1m 42s ✓ D Characteristics of Rectangles 2100 binary-search, bitmasks, brute-force 2m 12s ✗

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Codeforces Round 171 (Div. 2)

Codeforces Round 171 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 1400-1400 | Time: 1m 28s Problem Name Rating Tags Solve Time Verified A Point on Spiral 1400 brute-force, geometry, implementation 1m 28s ✓

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Codeforces Round 102 (Div. 2)

Codeforces Round 102 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1200 | Time: 4m 38s Problem Name Rating Tags Solve Time Verified A Help Vasilisa the Wise 2 1000 brute-force, math 2m 19s ✓ B Help Kingdom of Far Far Away 2 1200 implementation, strings 2m 19s ✓

Practice › Codeforces Solutions › Codeforces Round 147 (Div. 2) ›

CF 237A - Free Cash

CF 237A - Free Cash Rating: 1000 Tags: implementation Solve time: 3m 17s Verified: yes Solution Problem Understanding We are given the arrival times of customers visiting a cafe during one day. Every customer is served in less than one minute, so the only time a queue can appear is when several customers arrive at exactly the same minute. The cafe needs enough cash desks operating so that every customer...

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Codeforces Round 251 (Div. 2)

Codeforces Round 251 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 900-1700 | Time: 2m 9s Problem Name Rating Tags Solve Time Verified A Devu, the Singer and Churu, the Joker 900 greedy, implementation 1m 12s ✓ D Devu and his Brother 1700 binary-search, sortings, ternary-search 57s ✓

Practice › Codeforces Solutions › Codeforces Round 167 (Div. 2) ›

CF 272B - Dima and Sequence

CF 272B - Dima and Sequence Rating: 1400 Tags: implementation, math Solve time: 1m 30s Verified: yes Solution Problem Understanding We are given an array of positive integers. For every number x , a recursive function f(x) is defined as: $f(0)=0,\quad f(2x)=f(x),\quad f(2x+1)=f(x)+1$ The task is to count how many index pairs (i, j) with i < j satisfy f(ai) = f(aj) . The recursive definition looks unusual at first,...

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Codeforces Round 201 (Div. 2)

Codeforces Round 201 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 1100-1100 | Time: 1m 42s Problem Name Rating Tags Solve Time Verified B Fixed Points 1100 brute-force, implementation, math 1m 42s ✓

Practice › Codeforces Solutions › Codeforces Round 165 (Div. 2) ›

CF 270A - Fancy Fence

CF 270A - Fancy Fence Rating: 1100 Tags: geometry, implementation, math Solve time: 1m 12s Verified: yes Solution Problem Understanding We are asked to determine whether a robot, which can only make fence corners at a fixed angle a , can construct a regular polygon. A regular polygon is defined as a closed shape with all sides and all angles equal. The input consists of several test cases, each giving...

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Codeforces Round 253 (Div. 2)

Codeforces Round 253 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 800-800 | Time: 1m 19s Problem Name Rating Tags Solve Time Verified A Anton and Letters 800 constructive-algorithms, implementation 1m 19s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 10 ›

CF 10A - Power Consumption Calculation

CF 10A - Power Consumption Calculation Rating: 900 Tags: implementation Solve time: 1m 30s Verified: yes Solution Problem Understanding Tom uses his laptop during several disjoint time intervals. While he is actively using it, the laptop stays in normal mode and consumes P1 watts per minute. When he stops interacting with the laptop, the machine does not immediately switch to lower-power states. For the first T1 minutes of inactivity, it...

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Codeforces Beta Round 13

Codeforces Beta Round 13 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1000-2700 | Time: 7m 43s Problem Name Rating Tags Solve Time Verified A Numbers 1000 implementation, math 1m 3s ✓ B Letter A 2000 geometry, implementation 1m 45s ✓ C Sequence 2200 dp, sortings 1m 24s ✓ D Triangles 2600 dp, geometry 1m 38s ✓ E Holes 2700 data-structures, dsu 1m 53s ✓

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Codeforces Beta Round 93 (Div. 2 Only)

Codeforces Beta Round 93 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 900-1000 | Time: 3m 25s Problem Name Rating Tags Solve Time Verified A Wasted Time 900 geometry 1m 39s ✓ B Canvas Frames 1000 implementation 1m 46s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 71 ›

CF 79B - Colorful Field

CF 79B - Colorful Field Rating: 1400 Tags: implementation, sortings Solve time: 1m 19s Verified: yes Solution Problem Understanding We are asked to simulate planting crops on a rectangular field, but with a catch: some cells are wasteland. The field is represented as an n by m grid, with rows numbered from 1 to n and columns from 1 to m . Some cells contain waste, and the rest contain...

Practice › Codeforces Solutions › School Regional Team Contest, Saratov, 2011 ›

CF 120G - Boom

CF 120G - Boom Rating: 1800 Tags: implementation Solve time: 1m 17s Verified: yes Solution Problem Understanding We are simulating a simplified version of the party game "Boom" with multiple teams and cards. There are n teams, each with two players. Each player has an ability to explain words ( a ) and an ability to understand words ( b ). There is a deck of m cards, each containing...

Practice › Codeforces Solutions › Codeforces Beta Round 73 (Div. 1 Only) ›

CF 87D - Beautiful Road

CF 87D - Beautiful Road Rating: 2300 Tags: dfs and similar, dp, dsu, graphs, implementation, sortings, trees Solve time: 2m 12s Verified: yes Solution Problem Understanding We are given a weighted tree with n cities and n - 1 roads. Every ordered pair of distinct cities represents one military campaign, so there are n * (n - 1) total trips. For a trip from city u to city v ,...

Practice › Codeforces Solutions › Codeforces Beta Round 93 (Div. 2 Only) ›

CF 127B - Canvas Frames

CF 127B - Canvas Frames Rating: 1000 Tags: implementation Solve time: 1m 46s Verified: yes Solution Problem Understanding We are given a collection of sticks, where each stick has an integer length. A rectangular frame needs four sticks arranged as two equal pairs. If the frame is a square, then all four sticks must have the same length. The task is to build as many frames as possible without cutting...

Practice › Codeforces Solutions › Codeforces Beta Round 82 (Div. 2) ›

CF 106D - Treasure Island

CF 106D - Treasure Island Rating: 1700 Tags: brute force, implementation Solve time: 2m 25s Verified: yes Solution Problem Understanding We are given a grid representing an island with impassable sea cells and traversable land cells. Some of the land cells contain unique local sights labeled with uppercase letters. The problem provides a sequence of movement instructions, each specifying a direction (north, south, east, or west) and a number of...

Practice › Codeforces Solutions › Codeforces Beta Round 91 (Div. 1 Only) ›

CF 121D - Lucky Segments

CF 121D - Lucky Segments Rating: 2500 Tags: binary search, implementation, two pointers Solve time: 1m 59s Verified: yes Solution Problem Understanding We are asked to find the maximum number of "full lucky numbers" that can appear after adjusting segments of numbers. A lucky number is any positive integer whose digits consist only of 4 and 7. Each segment is a range [l_i, r_i] on the number line. A number...

Practice › Codeforces Solutions › School Team Contest 1 (Winter Computer School 2010/11) ›

CF 39J - Spelling Check

CF 39J - Spelling Check Rating: 1500 Tags: hashing, implementation, strings Solve time: 1m 34s Verified: yes Solution Problem Understanding We are given two lowercase strings. The first string is exactly one character longer than the second. We want to find every position in the first string such that removing the character at that position makes the two strings identical. The task is not to perform arbitrary edits. Only one...

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Codeforces Beta Round 33 (Codeforces format)

Codeforces Beta Round 33 (Codeforces format) Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1200-2600 | Time: 18m 29s Problem Name Rating Tags Solve Time Verified A What is for dinner? 1200 greedy, implementation 3m 53s ✓ B String Problem 1800 shortest-paths 7m 1s ✓ C Wonderful Randomized Sum 1800 greedy 3m 6s ✓ D Knights 2000 geometry, graphs, shortest-paths 1m 32s ✓ E Helper 2600 -...

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Codeforces Beta Round 46 (Div. 2)

Codeforces Beta Round 46 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2300 | Time: 8m 21s Problem Name Rating Tags Solve Time Verified A Sleuth 800 implementation 1m 21s ✓ B Sum 1500 math 1m 24s ✓ C Disposition 1700 constructive-algorithms, math 1m 48s ✓ D Game 1800 brute-force, dp, implementation 1m 47s ✓ E Common ancestor 2300 dp 2m 1s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 61 (Div. 2) ›

CF 66B - Petya and Countryside

CF 66B - Petya and Countryside Rating: 1100 Tags: brute force, implementation Solve time: 1m 25s Verified: yes Solution Problem Understanding We have a garden represented as a one-dimensional array of sections, each with a fixed height. Petya can create artificial rain above exactly one section , and water will flow to neighboring sections as long as their height is less than or equal to the section the water comes...

Practice › Codeforces Solutions › Codeforces Beta Round 98 (Div. 2) ›

CF 137A - Postcards and photos

CF 137A - Postcards and photos Rating: 900 Tags: implementation Solve time: 1m 28s Verified: yes Solution Problem Understanding We are given a string made of two characters, C and P . Each character represents one object hanging on the wall. C means postcard, P means photo. Polycarpus removes objects from left to right. He cannot skip positions, and at any moment he may carry only one type of object....

Practice › Codeforces Solutions › Codeforces Beta Round 95 (Div. 2) ›

CF 131B - Opposites Attract

CF 131B - Opposites Attract Rating: 1200 Tags: implementation, math Solve time: 1m 34s Verified: yes Solution Problem Understanding We are asked to count all pairs of clients whose assigned numbers are exact opposites. Each client has a number between -10 and 10, and a pair is valid if one client has number $x$ and the other has number $-x$. Zero is considered its own opposite, so two clients with...

Practice › Codeforces Solutions › Codeforces Beta Round 70 (Div. 2) ›

CF 78B - Easter Eggs

CF 78B - Easter Eggs Rating: 1200 Tags: constructive algorithms, implementation Solve time: 1m 59s Verified: no Solution Problem Understanding We need to build a circular sequence of colors for n eggs. There are exactly seven available colors: R, O, Y, G, B, I, V Two conditions must hold simultaneously. First, every color must appear at least once. Second, every block of four consecutive eggs on the circle must contain...

Practice › Codeforces Solutions › School Personal Contest #2 (Winter Computer School 2010/11) - Codeforces Beta Round 43 (ACM-ICPC Rules) ›

CF 46B - T-shirts from Sponsor

CF 46B - T-shirts from Sponsor Rating: 1100 Tags: implementation Solve time: 1m 13s Verified: yes Solution Problem Understanding We are given a limited stock of T-shirts in five sizes: S, M, L, XL, and XXL. Each participant in the contest has a preferred size. Participants arrive in a fixed order and try to pick the T-shirt closest to their preferred size. If their preferred size is available, they take...

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Codeforces Testing Round 3

Codeforces Testing Round 3 Type: Special | Problems: 3 | Verified: 2/3 | Rating range: 1200-2200 | Time: 5m 24s Problem Name Rating Tags Solve Time Verified A Average Numbers 1200 brute-force, implementation 1m 39s ✓ B Pairs of Numbers 1900 brute-force, dfs-and-similar, math 1m 30s ✓ C Swaps 2200 constructive-algorithms, graphs, greedy 2m 15s ✗

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Codeforces Beta Round 8

Codeforces Beta Round 8 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1200-2600 | Time: 6m 59s Problem Name Rating Tags Solve Time Verified A Train and Peter 1200 strings 1m 17s ✓ B Obsession with Robots 1400 constructive-algorithms, graphs, implementation 56s ✓ C Looking for Order 2000 bitmasks, dp 1m 48s ✓ D Two Friends 2600 binary-search, geometry 1m 54s ✓ E Beads 2600 dp, graphs...

Practice › Codeforces Solutions ›

Codeforces Beta Round 73 (Div. 1 Only)

Codeforces Beta Round 73 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1500-2600 | Time: 9m 48s Problem Name Rating Tags Solve Time Verified A Trains 1500 implementation, math 1m 15s ✓ B Vasya and Types 1800 implementation, strings 1m 56s ✓ C Interesting Game 2000 dp, games, math 1m 9s ✓ D Beautiful Road 2300 dfs-and-similar, dp, dsu 2m 12s ✓ E...

Practice › Codeforces Solutions ›

Codeforces Beta Round 14 (Div. 2)

Codeforces Beta Round 14 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-1900 | Time: 7m 42s Problem Name Rating Tags Solve Time Verified A Letter 800 implementation 1m 8s ✓ B Young Photographer 1000 implementation 1m 20s ✓ C Four Segments 1700 brute-force, constructive-algorithms, geometry 1m 48s ✓ D Two Paths 1900 dfs-and-similar, dp, graphs 1m 27s ✓ E Camels 1900 dp 1m...

Practice › Codeforces Solutions › Codeforces Beta Round 28 (Codeforces format) ›

CF 28A - Bender Problem

CF 28A - Bender Problem Rating: 1600 Tags: implementation Solve time: 1m 17s Verified: yes Solution Problem Understanding We are given a sequence of nails in the plane, each with integer coordinates, and a collection of straight rods. The nails define the vertices of a closed polyline that only moves along horizontal or vertical segments. The goal is to assign some rods to some nails so that each rod can...

Practice › Codeforces Solutions ›

Codeforces Beta Round 68

Codeforces Beta Round 68 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1000-2800 | Time: 22m 53s Problem Name Rating Tags Solve Time Verified A Room Leader 1000 implementation 1m 35s ✓ B Train 1500 dp, games, greedy 2m 11s ✓ C Chessboard Billiard 2100 dfs-and-similar, dsu, graphs 1m 36s ✓ D Hanger 2400 data-structures 1m 7s ✓ E Shift It! 2800 constructive-algorithms 16m 24s ✗

Practice › Codeforces Solutions › Codeforces Beta Round 96 (Div. 2) ›

CF 133B - Unary

CF 133B - Unary Rating: 1200 Tags: implementation Solve time: 1m 30s Verified: yes Solution Problem Understanding We are given a short Brainfuck program consisting of characters like + , - , > , < , and so on. Each command corresponds to a fixed 4-bit binary string. After replacing every character with its binary code, we concatenate all those 4-bit chunks into one long binary number. The task is...

Practice › Codeforces Solutions › Codeforces Beta Round 29 (Div. 2, Codeforces format) ›

CF 29B - Traffic Lights

CF 29B - Traffic Lights Rating: 1500 Tags: implementation Solve time: 1m 23s Verified: yes Solution Problem Understanding A car starts at point A and moves along a straight road toward point B. The total distance is l meters, and the car always moves at a fixed speed v . Somewhere along the road, exactly d meters from the start, there is a traffic light. The traffic light alternates between...

Practice › Codeforces Solutions › Codeforces Beta Round 67 (Div. 2) ›

CF 75D - Big Maximum Sum

CF 75D - Big Maximum Sum Rating: 2000 Tags: data structures, dp, greedy, implementation, math, trees Solve time: 1m 34s Verified: yes Solution Problem Understanding We are given a set of small arrays and a sequence of indexes indicating how to concatenate them into one larger array. Once the large array is built in this way, the goal is to find the maximum sum of a contiguous subarray. This is...

Practice › Codeforces Solutions › Unknown Language Round 2 ›

CF 72B - INI-file

CF 72B - INI-file Rating: 2200 Tags: *special, implementation Solve time: 1m 45s Verified: yes Solution Problem Understanding We are given a text file written in INI format. Every meaningful line is either a section declaration such as [network] or a key-value assignment such as port=8080 . Spaces around keys, values, and section brackets are irrelevant and must be removed in the final output. Lines whose first non-space character is...

Practice › Codeforces Solutions › Codeforces Beta Round 32 (Div. 2, Codeforces format) ›

CF 32D - Constellation

CF 32D - Constellation Rating: 1600 Tags: implementation Solve time: 59s Verified: yes Solution Problem Understanding We are given a 2D grid of size n by m , each cell either containing a star * or empty . . The task is to locate constellations shaped like a cross. A cross is centered at a star and extends exactly x squares vertically and horizontally in all four directions, with x...

Practice › Codeforces Solutions › Codeforces Beta Round 91 (Div. 1 Only) ›

CF 121A - Lucky Sum

CF 121A - Lucky Sum Rating: 1100 Tags: implementation Solve time: 1m 36s Verified: yes Solution Problem Understanding We need to evaluate a sum over an interval [l, r] . For every integer x in that range, we compute next(x) , where next(x) means the smallest lucky number greater than or equal to x . A lucky number is a positive integer whose decimal digits are only 4 and 7...

Practice › Codeforces Solutions › Codeforces Beta Round 69 (Div. 1 Only) ›

CF 77D - Domino Carpet

CF 77D - Domino Carpet Rating: 2300 Tags: dp, implementation Solve time: 1m 59s Verified: no Solution Problem Understanding We are tasked with counting the number of ways to cover an n × m grid using standard dominoes of size 1 × 2 , where each domino can be placed either vertically or horizontally. The input is presented as a visually rich ASCII depiction of the grid, with each square...

Practice › Codeforces Solutions › Codeforces Beta Round 97 (Div. 1) ›

CF 135A - Replacement

CF 135A - Replacement Rating: 1300 Tags: greedy, implementation, sortings Solve time: 1m 34s Verified: yes Solution Problem Understanding We start with an array of positive integers. We must change exactly one element to a different value, still between 1 and 10^9 . After that single replacement, we sort the array in non-decreasing order. The task is to produce the lexicographically smallest possible sorted array after performing exactly one replacement....

Practice › Codeforces Solutions › Yandex.Algorithm Open 2011: Qualification 1 ›

CF 81E - Pairs

CF 81E - Pairs Rating: 2700 Tags: dfs and similar, dp, dsu, graphs, implementation, trees Solve time: 3m 30s Verified: no Solution Problem Understanding Each student points to exactly one other student, the person they consider their best friend. We may create a pair (a, b) only if either a chose b or b chose a . Every student can belong to at most one pair. Among all valid sets...

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Codeforces Beta Round 27 (Codeforces format, Div. 2)

Codeforces Beta Round 27 (Codeforces format, Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1200-2200 | Time: 6m 38s Problem Name Rating Tags Solve Time Verified A Next Test 1200 implementation, sortings 1m 13s ✓ B Tournament 1300 bitmasks, brute-force, dfs-and-similar 1m 3s ✓ C Unordered Subsequence 1900 constructive-algorithms, greedy 1m 18s ✗ D Ring Road 2 2200 2-sat, dfs-and-similar, dsu 1m 30s ✓...

Practice › Codeforces Solutions › Codeforces Testing Round 2 ›

CF 125B - Simple XML

CF 125B - Simple XML Rating: 1000 Tags: implementation Solve time: 1m 41s Verified: yes Solution Problem Understanding We are given a string that represents a valid XML-like structure. Every tag is either an opening tag like <a> or a closing tag like </a> , where the tag name is a single lowercase letter. The string is guaranteed to be valid, which means every opening tag has a matching closing...

Practice › Codeforces Solutions › Codeforces Beta Round 34 (Div. 2) ›

CF 34C - Page Numbers

CF 34C - Page Numbers Rating: 1300 Tags: expression parsing, implementation, sortings, strings Solve time: 1m 7s Verified: yes Solution Problem Understanding We are asked to process a user-entered sequence of page numbers for printing. The input is a single string of positive integers separated by commas, such as 1,2,3,1,1,2,6,6,2 . Some numbers may repeat, possibly non-consecutively. Our goal is to produce a condensed, canonical representation: consecutive numbers are merged...

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Codeforces Beta Round 48

Codeforces Beta Round 48 Type: Beta | Problems: 6 | Verified: 4/6 | Rating range: 1300-2800 | Time: 13m 36s Problem Name Rating Tags Solve Time Verified A Cheaterius's Problem 1300 implementation 1m 37s ✓ B bHTML Tables Analisys 1700 expression-parsing 3m 37s ✓ C Three Base Stations 1800 binary-search, greedy 2m 13s ✗ D Geometrical problem 2200 implementation 1m 55s ✓ E Pentagon 2400 combinatorics, graphs, matrices 2m 2s...

Practice › Codeforces Solutions ›

Unknown Language Round 1

Unknown Language Round 1 Type: Special | Problems: 9 | Verified: 9/9 | Rating range: 1300-2400 | Time: 14m 26s Problem Name Rating Tags Solve Time Verified A Factorial 1300 *special, implementation 1m 13s ✓ B Expression 1500 *special, expression-parsing 1m 39s ✓ C Table 1600 *special, greedy, implementation 1m 25s ✓ D Presents 1800 *special, greedy 1m 40s ✓ E Prime Segment 1800 *special, brute-force, math 1m 28s ✓...

Practice › Codeforces Solutions › School Team Contest 2 (Winter Computer School 2010/11) ›

CF 44C - Holidays

CF 44C - Holidays Rating: 1300 Tags: implementation Solve time: 1m 24s Verified: yes Solution Problem Understanding We are asked to verify a watering schedule for flowers over a set of consecutive holiday days. Each day must be watered exactly once. The schedule specifies, for each of several people, the range of days they are assigned to water the flowers. The goal is to detect whether there is any mistake:...

Practice › Codeforces Solutions › Codeforces Beta Round 14 (Div. 2) ›

CF 14C - Four Segments

CF 14C - Four Segments Rating: 1700 Tags: brute force, constructive algorithms, geometry, implementation, math Solve time: 1m 48s Verified: yes Solution Problem Understanding We are given exactly four line segments on the 2D plane. Every segment is axis-aligned, or may even degenerate into a single point. The task is to decide whether these four segments together form the border of one rectangle with positive area, where all rectangle sides...

Practice › Codeforces Solutions › Codeforces Beta Round 42 (Div. 2) ›

CF 43D - Journey

CF 43D - Journey Rating: 2000 Tags: brute force, constructive algorithms, implementation Solve time: 1m 39s Verified: yes Solution Problem Understanding We have an n × m grid. The king starts at the top-left cell (1,1) and must end there as well. Every other cell must be visited exactly once. Normal movement is allowed only between side-adjacent cells, but we may additionally install directed teleporters. A teleporter is attached to...

Practice › Codeforces Solutions ›

Codeforces Beta Round 3

Codeforces Beta Round 3 Type: Beta | Problems: 4 | Verified: 4/4 | Rating range: 1000-2600 | Time: 14m 42s Problem Name Rating Tags Solve Time Verified A Shortest path of the king 1000 greedy, shortest-paths 4m 37s ✓ B Lorry 1900 greedy, sortings 4m 5s ✓ C Tic-tac-toe 1800 brute-force, games, implementation 4m 37s ✓ D Least Cost Bracket Sequence 2600 greedy 1m 23s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 84 (Div. 2 Only) ›

CF 110A - Nearly Lucky Number

CF 110A - Nearly Lucky Number Rating: 800 Tags: implementation Solve time: 2m 36s Verified: yes Solution Problem Understanding We are given a positive integer and need to decide whether it is a nearly lucky number. A number is considered nearly lucky if the count of its lucky digits-digits equal to 4 or 7-is itself a lucky number. A lucky number contains only 4s and 7s in its decimal representation....

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Codeforces Beta Round 92 (Div. 1 Only)

Codeforces Beta Round 92 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1300-2500 | Time: 14m 53s Problem Name Rating Tags Solve Time Verified A Prime Permutation 1300 implementation, number-theory, strings 2m 19s ✗ B Squares 1800 math 5m 4s ✓ C Brackets 2300 combinatorics, dp, greedy 2m 19s ✓ D String 2300 string-suffix-structures 2m 32s ✓ E Maze 2500 dfs-and-similar, dp, probabilities...

Practice › Codeforces Solutions › Codeforces Beta Round 40 (Div. 2) ›

CF 41A - Translation

CF 41A - Translation Rating: 800 Tags: implementation, strings Solve time: 1m 14s Verified: yes Solution Problem Understanding We are given two lowercase strings. The first string is a word in one language, and the second string is supposed to be its translation into another language where every word is written backwards. The task is simply to check whether the second string is exactly the reverse of the first one....

Practice › Codeforces Solutions › Codeforces Beta Round 55 (Div. 2) ›

CF 59B - Fortune Telling

CF 59B - Fortune Telling Rating: 1200 Tags: implementation, number theory Solve time: 1m 57s Verified: no Solution Problem Understanding Marina can pick any subset of flowers from the field. Each flower has a certain number of petals, and she will pluck all petals from all chosen flowers one by one. The phrases alternate between "Loves" and "Doesn't love" , starting from "Loves" on the first petal. The final phrase...

Practice › Codeforces Solutions › Codeforces Beta Round 13 ›

CF 13A - Numbers

CF 13A - Numbers Rating: 1000 Tags: implementation, math Solve time: 1m 3s Verified: yes Solution Problem Understanding We are asked to compute the average sum of digits of a number A when it is expressed in all bases from 2 up to A - 1. The input is a single integer A between 3 and 1000. The output should be an irreducible fraction representing the sum of all digit...

Practice › Codeforces Solutions › Codeforces Beta Round 26 (Codeforces format) ›

CF 26C - Parquet

CF 26C - Parquet Rating: 2000 Tags: combinatorics, constructive algorithms, greedy, implementation Solve time: 2m 9s Verified: no Solution Problem Understanding We are asked to tile a rectangular floor of size n × m using three types of parquet planks. The first type is a 1×2 horizontal plank, the second is a 2×1 vertical plank, and the third is a 2×2 square plank. The goal is to cover the entire...

Practice › Codeforces Solutions › School Personal Contest #1 (Winter Computer School 2010/11) - Codeforces Beta Round 38 (ACM-ICPC Rules) ›

CF 38A - Army

CF 38A - Army Rating: 800 Tags: implementation Solve time: 1m 18s Verified: yes Solution Problem Understanding Vasya currently holds rank a in the army and wants to eventually reach rank b . Moving from rank i to rank i + 1 requires a fixed number of years, stored in the array d . The array has length n - 1 because there are exactly n - 1 transitions between...

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Codeforces Beta Round 91 (Div. 1 Only)

Codeforces Beta Round 91 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1100-2500 | Time: 9m 56s Problem Name Rating Tags Solve Time Verified A Lucky Sum 1100 implementation 1m 36s ✓ B Lucky Transformation 1500 strings 2m 26s ✓ C Lucky Permutation 1900 brute-force, combinatorics, number-theory 1m 34s ✓ D Lucky Segments 2500 binary-search, implementation, two-pointers 1m 59s ✓ E Lucky Array...

Practice › Codeforces Solutions › Codeforces Beta Round 96 (Div. 2) ›

CF 133A - HQ9+

CF 133A - HQ9+ Rating: 900 Tags: implementation Solve time: 1m 4s Verified: yes Solution Problem Understanding The task is to analyze a program written in the esoteric HQ9+ language and determine whether executing it will produce any visible output. The program is provided as a single string consisting of printable ASCII characters. In HQ9+, only four characters have operational meaning: "H" prints "Hello, World!", "Q" prints the program itself,...

Practice › Codeforces Solutions › Codeforces Beta Round 53 ›

CF 57B - Martian Architecture

CF 57B - Martian Architecture Rating: 1600 Tags: implementation Solve time: 1m 37s Verified: yes Solution Problem Understanding Each construction describes a staircase placed on a one-dimensional line of cells. A staircase starts at cell l , ends at cell r , and adds heights in an arithmetic progression. If the starting height is x , then the added stones are: x at l x + 1 at l +...

Practice › Codeforces Solutions › Codeforces Beta Round 6 (Div. 2 Only) ›

CF 6B - President's Office

CF 6B - President's Office Rating: 1100 Tags: implementation Solve time: 1m 18s Verified: yes Solution Problem Understanding The office is represented as a rectangular grid. Every uppercase letter represents part of a desk, and all cells with the same letter belong to the same rectangular desk. The president’s desk color is given as c . A deputy is any desk that shares a side with at least one cell...

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Codeforces Beta Round 74 (Div. 2 Only)

Codeforces Beta Round 74 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1100 | Time: 3m 17s Problem Name Rating Tags Solve Time Verified A Cableway 1000 greedy, math 1m 33s ✓ B African Crossword 1100 implementation, strings 1m 44s ✓

Practice › Codeforces Solutions ›

Codeforces Beta Round 65 (Div. 2)

Codeforces Beta Round 65 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 800-2200 | Time: 8m 23s Problem Name Rating Tags Solve Time Verified A Way Too Long Words 800 strings 1m 28s ✓ B Progress Bar 1300 implementation, math 1m 7s ✓ C Round Table Knights 1600 dp, math, number-theory 1m 40s ✓ D Solitaire 2200 brute-force, implementation 2m 18s ✓ E Nuclear...

Practice › Codeforces Solutions › Unknown Language Round 2 ›

CF 72H - Reverse It!

CF 72H - Reverse It! Rating: 1600 Tags: *special, implementation Solve time: 3m 28s Verified: yes Solution Problem Understanding The task is to reverse a number given as a string, taking care of signs and leading zeros. The input can be a very large integer, up to 10,000 digits, possibly with leading zeros. We need to remove those leading zeros first, reverse the remaining digits, and output the result as...

Practice › Codeforces Solutions › Codeforces Beta Round 74 (Div. 2 Only) ›

CF 90B - African Crossword

CF 90B - African Crossword Rating: 1100 Tags: implementation, strings Solve time: 1m 44s Verified: yes Solution Problem Understanding We are given a small grid of lowercase letters. A cell survives only if its letter is unique both inside its row and inside its column. If the same character appears somewhere else in the same row, that cell is removed. The same happens if the character appears somewhere else in...

Practice › Codeforces Solutions › Codeforces Beta Round 2 ›

CF 2A - Winner

Problem Understanding The game records a sequence of rounds. In each round, one player either gains or loses some number of points. At the end, the player with the highest total score should win. The tricky part appears when several players finish with the same highest score. In that situation, the winner is not chosen arbitrarily. Among all players whose final score equals the maximum value, we pick the one...

Practice › Codeforces Solutions › Codeforces Beta Round 97 (Div. 2) ›

CF 136B - Ternary Logic

CF 136B - Ternary Logic Rating: 1100 Tags: implementation, math Solve time: 1m 41s Verified: yes Solution Problem Understanding We are given two decimal integers, a and c . The computer in this problem does not use binary xor. Instead, it uses a ternary operation called tor . To apply tor , both numbers are written in base 3. If one number has fewer digits, we pad it with leading...

Practice › Codeforces Solutions › Codeforces Beta Round 94 (Div. 1 Only) ›

CF 128B - String

CF 128B - String Rating: 2100 Tags: brute force, constructive algorithms, hashing, implementation, string suffix structures, strings Solve time: 1m 21s Verified: yes Solution Problem Understanding We are given a string of lowercase letters and an integer k . The task is to generate all possible substrings of the string, sort them lexicographically, and return the k -th substring in that order. Substrings can repeat, so multiple identical substrings must...

Practice › Codeforces Solutions ›

School Team Contest 3 (Winter Computer School 2010/11)

School Team Contest 3 (Winter Computer School 2010/11) Type: Special | Problems: 10 | Verified: 7/10 | Rating range: 900-2500 | Time: 19m 28s Problem Name Rating Tags Solve Time Verified A Codecraft III 900 implementation 1m 14s ✓ B School 2200 dp, dsu 2m 6s ✓ C Dancing Lessons 1900 data-structures 1m 24s ✓ D Event Dates 1900 greedy, meet-in-the-middle, sortings 1m 35s ✓ E Director 2000 constructive-algorithms, greedy...

Practice › Codeforces Solutions › Codeforces Beta Round 58 ›

CF 62B - Tyndex.Brome

CF 62B - Tyndex.Brome Rating: 1800 Tags: binary search, implementation Solve time: 1m 18s Verified: yes Solution Problem Understanding The task is to compute a kind of "distance" between a user-entered address and a list of potential addresses, according to a specific error function. The user enters a string s of length k . Then there are n potential addresses, each a string of arbitrary length. For each character in...

Practice › Codeforces Solutions ›

Codeforces Beta Round 25 (Div. 2 Only)

Codeforces Beta Round 25 (Div. 2 Only) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1100-2200 | Time: 6m 12s Problem Name Rating Tags Solve Time Verified A IQ test 1300 brute-force 1m 7s ✓ B Phone numbers 1100 implementation 1m 24s ✓ C Roads in Berland 1900 graphs, shortest-paths 58s ✓ D Roads not only in Berland 1900 dsu, graphs, trees 1m 15s ✓ E...

Practice › Codeforces Solutions › Unknown Language Round 1 ›

CF 64C - Table

CF 64C - Table Rating: 1600 Tags: *special, greedy, implementation, math Solve time: 1m 25s Verified: yes Solution Problem Understanding We are given an $n \times m$ table filled with consecutive integers starting from 1. The filling is done row by row, left to right. For example, if $n=3$ and $m=4$, the table looks like this: 1 2 3 4 5 6 7 8 9 10 11 12 Then, the...

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Codeforces Beta Round 63 (Div. 2)

Codeforces Beta Round 63 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1000-2000 | Time: 9m 17s Problem Name Rating Tags Solve Time Verified A Young Physicist 1000 implementation, math 1m 43s ✓ B Bets 1200 greedy, implementation 2m 1s ✓ C Game 2000 implementation 2m 15s ✓ D Dot 1900 dp, games 1m 56s ✓ E Subsegments 1800 data-structures, implementation 1m 22s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 27 (Codeforces format, Div. 2) ›

CF 27A - Next Test

CF 27A - Next Test Rating: 1200 Tags: implementation, sortings Solve time: 1m 13s Verified: yes Solution Problem Understanding We are given the indices of tests that already exist in the system. Every index is a positive integer, and all indices are distinct. The task is to find the smallest positive integer that does not appear in the list. This is the classic "smallest missing positive" idea, but the constraints...

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Codeforces Beta Round 96 (Div. 1)

Codeforces Beta Round 96 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1300-2700 | Time: 9m 16s Problem Name Rating Tags Solve Time Verified A Turing Tape 1300 implementation 1m 39s ✓ B Piet 2100 implementation 1m 56s ✓ C Logo Turtle 1800 dp 1m 52s ✓ D Constants in the language of Shakespeare 2100 constructive-algorithms, dp, greedy 2m 2s ✗ E Bits of...

Practice › Codeforces Solutions › Codeforces Beta Round 13 ›

CF 13B - Letter A

CF 13B - Letter A Rating: 2000 Tags: geometry, implementation Solve time: 1m 45s Verified: yes Solution Problem Understanding We are given three line segments on a 2D plane. We must decide whether these three segments can be interpreted as the shape of the capital letter A. The structure of the letter is very rigid. Two segments must meet at a common endpoint and form the two slanted legs of...

Practice › Codeforces Solutions › Codeforces Beta Round 41 ›

CF 42A - Guilty --- to the kitchen!

CF 42A - Guilty --- to the kitchen! Rating: 1400 Tags: greedy, implementation Solve time: 1m 32s Verified: yes Solution Problem Understanding We want to cook soup using several ingredients that must appear in a fixed ratio. If the recipe says the proportions are a1, a2, ..., an , then the final soup must contain: a1 * x, a2 * x, ..., an * x litres of each ingredient for...

Practice › Codeforces Solutions › Codeforces Beta Round 4 (Div. 2 Only) ›

CF 4C - Registration System

CF 4C - Registration System Rating: 1300 Tags: data structures, hashing, implementation Solve time: 1m 42s Verified: yes Solution Problem Understanding We are building a username registration system. Every incoming request contains a desired username. If that username has never appeared before, registration succeeds immediately and we print OK . If the username is already taken, we must generate a new one by attaching the smallest positive integer suffix that...

Practice › Codeforces Solutions › Codeforces Beta Round 29 (Div. 2, Codeforces format) ›

CF 29C - Mail Stamps

CF 29C - Mail Stamps Rating: 1700 Tags: data structures, dfs and similar, graphs, implementation Solve time: 1m 37s Verified: no Solution Problem Understanding Each stamp describes a direct transfer between two cities. If the envelope contains n stamps, then the letter passed through exactly n + 1 cities in sequence. The route never revisits a city, so the entire journey forms a simple path. The stamps are unordered. We...

Practice › Codeforces Solutions › Codeforces Beta Round 36 ›

CF 36B - Fractal

CF 36B - Fractal Rating: 1600 Tags: implementation Solve time: 1m 52s Verified: yes Solution Problem Understanding We start with an n × n pattern consisting of black cells ( * ) and white cells ( . ). This pattern acts like a template. The fractal is built recursively. At the first level, the whole canvas is divided into n × n blocks, and every block corresponding to a black...

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Codeforces Beta Round 37

Codeforces Beta Round 37 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1000-2600 | Time: 8m 37s Problem Name Rating Tags Solve Time Verified A Towers 1000 sortings 53s ✓ B Computer Game 1800 greedy, implementation 1m 56s ✓ C Old Berland Language 1900 data-structures, greedy, trees 1m 42s ✓ D Lesson Timetable 2300 combinatorics, dp, math 2m 23s ✗ E Trial for Chief 2600 graphs, greedy,...

Practice › Codeforces Solutions › School Regional Team Contest, Saratov, 2011 ›

CF 120C - Winnie-the-Pooh and honey

CF 120C - Winnie-the-Pooh and honey Rating: 1100 Tags: implementation, math Solve time: 1m 39s Verified: yes Solution Problem Understanding We have several jars of honey, and each jar starts with some amount of honey. Winnie repeatedly chooses the jar that currently contains the most honey. When Winnie picks a jar, two things may happen. If the jar contains less than k kilos of honey, or if Winnie has already...

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Codeforces Beta Round 31 (Div. 2, Codeforces format)

Codeforces Beta Round 31 (Div. 2, Codeforces format) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1200-2400 | Time: 6m 52s Problem Name Rating Tags Solve Time Verified A Worms Evolution 1200 implementation 1m 46s ✓ B Sysadmin Bob 1500 greedy, implementation, strings 1m 11s ✓ C Schedule 1700 implementation 58s ✓ D Chocolate 2000 dfs-and-similar, implementation 59s ✓ E TV Game 2400 dp 1m 58s...

Practice › Codeforces Solutions › Codeforces Beta Round 41 ›

CF 42B - Game of chess unfinished

CF 42B - Game of chess unfinished Rating: 1700 Tags: implementation Solve time: 2m 3s Verified: yes Solution Problem Understanding We are given a chess position containing exactly four pieces on a standard 8×8 board. White has two rooks and one king, black has only a king. The position is already legal, meaning no two pieces share a square and the two kings are not adjacent. The task is to...

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Codeforces Beta Round 36

Codeforces Beta Round 36 Type: Beta | Problems: 5 | Verified: 2/5 | Rating range: 1300-2600 | Time: 9m 36s Problem Name Rating Tags Solve Time Verified A Extra-terrestrial Intelligence 1300 implementation 1m 21s ✓ B Fractal 1600 implementation 1m 52s ✓ C Bowls 2200 geometry, implementation 2m 5s ✗ D New Game with a Chess Piece 2300 games 1m 43s ✗ E Two Paths 2600 constructive-algorithms, dsu, graphs 2m...

Practice › Codeforces Solutions › Codeforces Beta Round 11 ›

CF 11A - Increasing Sequence

CF 11A - Increasing Sequence Rating: 900 Tags: constructive algorithms, implementation, math Solve time: 1m 24s Verified: yes Solution Problem Understanding We have an array of integers, and we want every element to become strictly larger than the one before it. The only operation allowed is choosing a single element and increasing it by exactly d . Every use of this operation counts as one move. The task is to...

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Yandex.Algorithm 2011: Finals

Yandex.Algorithm 2011: Finals Type: Special | Problems: 5 | Verified: 4/5 | Rating range: 2200-2700 | Time: 11m 24s Problem Name Rating Tags Solve Time Verified A Domino 2400 brute-force, implementation 2m 46s ✗ B Superset 2300 constructive-algorithms, divide-and-conquer 2m 12s ✓ C Winning Strategy 2400 binary-search, graphs, math 1m 44s ✓ D Robot in Basement 2700 bitmasks, brute-force, implementation 2m 39s ✓ E Leaders 2200 dfs-and-similar, dsu, graphs 2m...

Practice › Codeforces Solutions › Codeforces Beta Round 83 (Div. 2 Only) ›

CF 108A - Palindromic Times

CF 108A - Palindromic Times Rating: 1000 Tags: implementation, strings Solve time: 4m 56s Verified: yes Solution Problem Understanding The task is to find the next time on a 24-hour digital clock that reads as a palindrome. The input is a string formatted as "HH:MM", representing hours and minutes in 24-hour notation. A palindromic time reads the same forwards and backwards when ignoring the colon, such as "12:21" or "03:30"....

Practice › Codeforces Solutions › Codeforces Beta Round 48 ›

CF 51D - Geometrical problem

CF 51D - Geometrical problem Rating: 2200 Tags: implementation Solve time: 1m 55s Verified: yes Solution Problem Understanding We are given an integer array and must classify it into one of three categories. A sequence is considered a geometric progression if there exist real numbers $c$ and $b$ such that every element has the form $c \cdot b^{i-1}$. In simpler terms, consecutive elements must share the same ratio whenever the...

Practice › Codeforces Solutions › Codeforces Beta Round 55 (Div. 2) ›

CF 59A - Word

CF 59A - Word Rating: 800 Tags: implementation, strings Solve time: 1m 11s Verified: yes Solution Problem Understanding The task is to normalize the case of a single word so that either all letters are lowercase or all are uppercase. The decision depends on which case dominates in the input: if there are more uppercase letters than lowercase letters, the word should be transformed entirely to uppercase; otherwise, it should...

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Codeforces Beta Round 32 (Div. 2, Codeforces format)

Codeforces Beta Round 32 (Div. 2, Codeforces format) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2400 | Time: 6m 58s Problem Name Rating Tags Solve Time Verified A Reconnaissance 800 brute-force 1m 5s ✓ B Borze 800 expression-parsing, implementation 1m 17s ✓ C Flea 1700 math 1m 12s ✓ D Constellation 1600 implementation 59s ✓ E Hide-and-Seek 2400 geometry, implementation 2m 25s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 76 (Div. 1 Only) ›

CF 93A - Frames

CF 93A - Frames Rating: 1700 Tags: implementation Solve time: 1m 51s Verified: yes Solution Problem Understanding The folders are displayed in a grid with exactly m columns per row. Folder 1 is in the top-left corner, folder 2 is next to it, and so on. After every m folders we move to the next row. A rectangular frame selection toggles every folder inside the rectangle. If a folder is...

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Codeforces Testing Round 2

Codeforces Testing Round 2 Type: Special | Problems: 3 | Verified: 2/3 | Rating range: 1000-1600 | Time: 5m 4s Problem Name Rating Tags Solve Time Verified A Measuring Lengths in Baden 1400 math 1m 18s ✓ B Simple XML 1000 implementation 1m 41s ✓ C Hobbits' Party 1600 constructive-algorithms, greedy 2m 5s ✗

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Codeforces Beta Round 19

Codeforces Beta Round 19 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1400-2900 | Time: 16m 37s Problem Name Rating Tags Solve Time Verified A World Football Cup 1400 implementation 5m 51s ✓ B Checkout Assistant 1900 dp 3m 5s ✓ C Deletion of Repeats 2200 greedy, hashing, string-suffix-structures 2m 2s ✓ D Points 2800 data-structures 3m 49s ✓ E Fairy 2900 dfs-and-similar, divide-and-conquer, dsu 1m 50s...

Practice › Codeforces Solutions › Codeforces Beta Round 73 (Div. 2 Only) ›

CF 88B - Keyboard

CF 88B - Keyboard Rating: 1500 Tags: implementation Solve time: 1m 13s Verified: yes Solution Problem Understanding We are given a keyboard laid out in an n by m grid. Each key contains either a lowercase Latin letter or a special "Shift" key represented by S . Vasya wants to type a string using one hand as much as possible, but he can press two keys at once only if...

Practice › Codeforces Solutions › Codeforces Beta Round 92 (Div. 2 Only) ›

CF 124B - Permutations

CF 124B - Permutations Rating: 1400 Tags: brute force, combinatorics, implementation Solve time: 1m 34s Verified: yes Solution Problem Understanding We are given several strings of digits, all with the same length. We may choose one permutation of digit positions and apply it to every string. After rearranging the digits according to that shared permutation, each string becomes a new integer, possibly with leading zeroes. Our goal is to make...

Practice › Codeforces Solutions › Codeforces Beta Round 5 ›

CF 5B - Center Alignment

CF 5B - Center Alignment Rating: 1200 Tags: implementation, strings Solve time: 1m 24s Verified: yes Solution Problem Understanding We are given several lines of text. Every line may contain letters, digits, and spaces inside the line, but never at the beginning or end. The task is to print all lines inside a rectangular frame made of * characters. The inside width of the frame must equal the length of...

Practice › Codeforces Solutions › Codeforces Beta Round 18 (Div. 2 Only) ›

CF 18C - Stripe

CF 18C - Stripe Rating: 1200 Tags: data structures, implementation Solve time: 1m 43s Verified: yes Solution Problem Understanding We have a strip of cells, and each cell contains an integer. We may cut the strip only between adjacent cells, which splits the array into a left part and a right part. The task is to count how many cut positions produce two non-empty parts with equal sums. For example,...

Practice › Codeforces Solutions › Codeforces Beta Round 24 ›

CF 24B - F1 Champions

CF 24B - F1 Champions Rating: 1500 Tags: implementation Solve time: 2m 19s Verified: yes Solution Problem Understanding We are given the results of an entire Formula One season. Each race lists drivers from first place to last place. The championship winner depends on one of two ranking systems. In the original system, drivers are ranked primarily by total points. The top 10 positions in each race award fixed points:...

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Codeforces Beta Round 73 (Div. 2 Only)

Codeforces Beta Round 73 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1200-1500 | Time: 2m 30s Problem Name Rating Tags Solve Time Verified A Chord 1200 brute-force, implementation 1m 17s ✓ B Keyboard 1500 implementation 1m 13s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 10 ›

CF 10B - Cinema Cashier

CF 10B - Cinema Cashier Rating: 1500 Tags: dp, implementation Solve time: 1m 24s Verified: yes Solution Problem Understanding The problem describes a cinema hall in Berland with K rows and K seats per row, where K is always odd. Customers come in groups of size M and request consecutive seats. The program’s task is to allocate a segment of M consecutive seats in a row such that the chosen...

Practice › Codeforces Solutions › Codeforces Testing Round 3 ›

CF 134A - Average Numbers

CF 134A - Average Numbers Rating: 1200 Tags: brute force, implementation Solve time: 1m 39s Verified: yes Solution Problem Understanding We are given an array of positive integers. For every position, we remove that element and compute the arithmetic mean of the remaining numbers. We must find all positions where the removed value itself is exactly equal to that mean. Suppose the array is [1, 2, 3, 4, 5] ....

Practice › Codeforces Solutions › Codeforces Beta Round 86 (Div. 1 Only) ›

CF 113E - Sleeping

CF 113E - Sleeping Rating: 2700 Tags: combinatorics, implementation, math Solve time: 1m 59s Verified: yes Solution Problem Understanding We are asked to count the number of times a digital clock shows a moment where at least k digits change simultaneously while Vasya is watching it. The clock is not necessarily 24-hour or 60-minute - it has h hours and m minutes, where both are arbitrary integers up to 10^9....

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Codeforces Beta Round 94 (Div. 2 Only)

Codeforces Beta Round 94 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 900-1200 | Time: 3m 59s Problem Name Rating Tags Solve Time Verified A Cookies 900 implementation 1m 44s ✓ B Students and Shoelaces 1200 brute-force, dfs-and-similar, graphs 2m 15s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 48 ›

CF 51A - Cheaterius's Problem

CF 51A - Cheaterius's Problem Rating: 1300 Tags: implementation Solve time: 1m 37s Verified: yes Solution Problem Understanding Each amulet is a 2 x 2 square filled with numbers from 1 to 6 . We can think of it as four cells: a b c d Two amulets belong to the same pile if one can be rotated into the other. Flipping is forbidden, only rotations by 90° , 180°...

Practice › Codeforces Solutions › Unknown Language Round 3 ›

CF 100G - Name the album

CF 100G - Name the album Rating: 1800 Tags: *special, data structures, implementation Solve time: 1m 50s Verified: yes Solution Problem Understanding Aryo wants to choose a title for a new album from a list of candidate names. Some names have already been used in previous years. His decision rule has two layers. If a candidate name has never been used before, that is the best possible choice. Among all...

Practice › Codeforces Solutions › Codeforces Beta Round 36 ›

CF 36A - Extra-terrestrial Intelligence

CF 36A - Extra-terrestrial Intelligence Rating: 1300 Tags: implementation Solve time: 1m 21s Verified: yes Solution Problem Understanding We are given a binary string representing Vasya's observations over several days. A character '1' means a signal was received on that day, while '0' means no signal appeared. The task is to determine whether the received signals follow a perfectly regular pattern. More precisely, if we look at the positions of...

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School Personal Contest #1 (Winter Computer School 2010/11) - Codeforces Beta Round 38 (ACM-ICPC Rules)

School Personal Contest #1 (Winter Computer School 2010/11) - Codeforces Beta Round 38 (ACM-ICPC Rules) Type: Beta | Problems: 8 | Verified: 5/8 | Rating range: 800-2400 | Time: 13m 48s Problem Name Rating Tags Solve Time Verified A Army 800 implementation 1m 18s ✓ B Chess 1200 brute-force, implementation, math 2m ✗ C Blinds 1400 brute-force 1m 7s ✓ D Vasya the Architect 1900 implementation 1m 38s ✓ E...

Practice › Codeforces Solutions › Codeforces Beta Round 87 (Div. 2 Only) ›

CF 116B - Little Pigs and Wolves

CF 116B - Little Pigs and Wolves Rating: 1100 Tags: greedy, implementation Solve time: 2m 30s Verified: yes Solution Problem Understanding We have a small rectangular grid where each cell is either empty, contains a pig, or contains a wolf. A wolf may eat one pig that is directly adjacent to it in one of the four cardinal directions. Once a pig is eaten, it disappears and cannot be eaten...

Practice › Codeforces Solutions › School Personal Contest #1 (Winter Computer School 2010/11) - Codeforces Beta Round 38 (ACM-ICPC Rules) ›

CF 38B - Chess

CF 38B - Chess Rating: 1200 Tags: brute force, implementation, math Solve time: 2m Verified: no Solution Problem Understanding We are given the positions of two chess pieces on a standard 8 × 8 board, one rook and one knight. Their starting positions are guaranteed to be safe, meaning the rook does not attack the knight and the knight does not attack the rook. We must place one more knight...

Practice › Codeforces Solutions › Codeforces Beta Round 8 ›

CF 8B - Obsession with Robots

CF 8B - Obsession with Robots Rating: 1400 Tags: constructive algorithms, graphs, implementation Solve time: 56s Verified: yes Solution Problem Understanding We are asked to analyze a robot's path on an infinite 2D grid. The robot can move up, down, left, or right, and its moves are recorded as a string of the characters U, D, L, R. The challenge is to determine whether there exists any possible arrangement of...

Practice › Codeforces Solutions › Codeforces Beta Round 24 ›

CF 24C - Sequence of points

CF 24C - Sequence of points Rating: 1800 Tags: geometry, implementation, math Solve time: 2m 35s Verified: yes Solution Problem Understanding We are given a sequence of points on the 2D integer grid: a starting point M0 and a sequence of n points A0, A1, …, An-1, where n is always odd. We then define a new sequence M1, M2, … where each Mi is the reflection of Mi-1 over...

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Codeforces Beta Round 79 (Div. 1 Only)

Codeforces Beta Round 79 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1200-2500 | Time: 11m 56s Problem Name Rating Tags Solve Time Verified A Homework 1200 greedy 2m 5s ✓ B Buses 1700 binary-search, data-structures, dp 1m 57s ✓ C Vectors 2000 implementation, math 2m 22s ✓ D Castle 2300 dp, greedy, probabilities 2m 6s ✓ E Candies and Stones 2500 divide-and-conquer,...

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Codeforces Beta Round 52 (Div. 2)

Codeforces Beta Round 52 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1000-2200 | Time: 8m 47s Problem Name Rating Tags Solve Time Verified A Bar 1000 implementation 1m 28s ✓ B Spoilt Permutation 1300 implementation 1m 42s ✓ C Corporation Mail 1700 data-structures, expression-parsing, implementation 1m 33s ✓ D Changing a String 2100 dp 2m 12s ✓ E Domino Principle 2200 binary-search, data-structures,...

Practice › Codeforces Solutions › School Team Contest 1 (Winter Computer School 2010/11) ›

CF 39H - Multiplication Table

CF 39H - Multiplication Table Rating: 1300 Tags: implementation Solve time: 1m 33s Verified: no Solution Problem Understanding The task is to generate a multiplication table for numbers in a positional numeral system with a base k . Unlike the decimal system, the digits in this system range from 0 up to k-1 . Petya wants to see products of numbers from 1 to k-1 expressed in this system. The...

Practice › Codeforces Solutions › Yandex.Algorithm 2011: Round 1 ›

CF 85D - Sum of Medians

CF 85D - Sum of Medians Rating: 2300 Tags: binary search, brute force, data structures, implementation Solve time: 1m 18s Verified: yes Solution Problem Understanding We are asked to maintain a dynamic set of positive integers under three operations: adding a number, deleting a number, and computing the sum of medians of every consecutive group of five elements after sorting the set. A median in a group of five is...

Practice › Codeforces Solutions › Codeforces Beta Round 49 (Div. 2) ›

CF 53B - Blog Photo

CF 53B - Blog Photo Rating: 1700 Tags: binary search, implementation Solve time: 2m 21s Verified: yes Solution Problem Understanding We are given the dimensions of an uploaded photo, height h and width w . We want to cut out a smaller rectangle from it. The cut rectangle must satisfy three conditions. First, its dimensions must be integers. Second, its aspect ratio must stay within the allowed range: $0.8 \leq...

Practice › Codeforces Solutions › Codeforces Beta Round 79 (Div. 2 Only) ›

CF 102B - Sum of Digits

CF 102B - Sum of Digits Rating: 1000 Tags: implementation Solve time: 1m 54s Verified: yes Solution Problem Understanding The problem asks us to repeatedly replace a number with the sum of its digits until the number becomes a single-digit number. The input is a number n that can be extremely large, up to 10 million digits. The output is the number of transformations needed to reach a one-digit number....

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Codeforces Beta Round 29 (Div. 2, Codeforces format)

Codeforces Beta Round 29 (Div. 2, Codeforces format) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 1000-2400 | Time: 6m 47s Problem Name Rating Tags Solve Time Verified A Spit Problem 1000 brute-force 1m 12s ✓ B Traffic Lights 1500 implementation 1m 23s ✓ C Mail Stamps 1700 data-structures, dfs-and-similar, graphs 1m 37s ✗ D Ant on the Tree 2000 constructive-algorithms, dfs-and-similar, trees 1m 19s ✓...

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Codeforces Beta Round 56

Codeforces Beta Round 56 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1300-2600 | Time: 11m 17s Problem Name Rating Tags Solve Time Verified A Where Are My Flakes? 1300 implementation, two-pointers 1m 40s ✓ B Serial Time! 1400 dfs-and-similar, dsu 2m 8s ✗ C Mushroom Strife 2100 brute-force, dfs-and-similar 2m 15s ✓ D Savior 2500 brute-force, dsu, math 2m 1s ✓ E Mushroom Gnomes 2600 math,...

Practice › Codeforces Solutions › Codeforces Beta Round 70 (Div. 2) ›

CF 78A - Haiku

CF 78A - Haiku Rating: 800 Tags: implementation, strings Solve time: 3m 30s Verified: yes Solution Problem Understanding We are given three lines representing the three phrases of a poem. A valid haiku must contain exactly 5 vowel letters in the first phrase, 7 in the second, and 5 in the third. For this problem, syllables are simplified into vowel counts. Only the lowercase letters a , e , i...

Practice › Codeforces Solutions › Codeforces Beta Round 36 ›

CF 36E - Two Paths

CF 36E - Two Paths Rating: 2600 Tags: constructive algorithms, dsu, graphs, implementation Solve time: 2m 35s Verified: no Solution Problem Understanding Each paper describes an undirected edge between two cities. We are told that all papers came from exactly two travel journals. Inside one journal, the traveler wrote down the sequence of roads they traversed, and a road may appear multiple times because the traveler could reuse it. The...

Practice › Codeforces Solutions › Codeforces Beta Round 96 (Div. 1) ›

CF 132B - Piet

CF 132B - Piet Rating: 2100 Tags: implementation Solve time: 1m 56s Verified: yes Solution Problem Understanding We are asked to simulate a simplified Piet interpreter on a small rectangular grid. Each cell is a pixel with a color between 0 and 9, where 0 is black and other digits are colored blocks. Colored blocks are always rectangular and connected, so every color cluster forms a perfect rectangle. Black pixels...

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Codeforces Beta Round 55 (Div. 2)

Codeforces Beta Round 55 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 800-2000 | Time: 8m 58s Problem Name Rating Tags Solve Time Verified A Word 800 implementation, strings 1m 11s ✓ B Fortune Telling 1200 implementation, number-theory 1m 57s ✗ C Title 1600 expression-parsing 1m 53s ✓ D Team Arrangement 2000 constructive-algorithms, greedy, implementation 2m 39s ✗ E Shortest Path 2000 graphs, shortest-paths...

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Unknown Language Round 2

Unknown Language Round 2 Type: Special | Problems: 9 | Verified: 8/9 | Rating range: 1000-2300 | Time: 21m 37s Problem Name Rating Tags Solve Time Verified A Goshtasp, Vishtasp and Eidi 1800 *special, greedy, math 1m 18s ✓ B INI-file 2200 *special, implementation 1m 45s ✓ C Extraordinarily Nice Numbers 1200 *special, math 1m 26s ✓ D Perse-script 2300 *special, expression-parsing 1m 55s ✗ E Ali goes shopping 1800...

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Codeforces Beta Round 97 (Div. 1)

Codeforces Beta Round 97 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1300-3000 | Time: 9m 14s Problem Name Rating Tags Solve Time Verified A Replacement 1300 greedy, implementation, sortings 1m 34s ✓ B Rectangle and Square 1600 brute-force, geometry, math 2m 3s ✓ C Zero-One 1900 constructive-algorithms, games, greedy 1m 50s ✓ D Cycle 2500 brute-force, dfs-and-similar, implementation 1m 50s ✓ E Weak...

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Codeforces Beta Round 61 (Div. 2)

Codeforces Beta Round 61 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 1100-2000 | Time: 9m 20s Problem Name Rating Tags Solve Time Verified A Petya and Java 1300 implementation, strings 1m 33s ✓ B Petya and Countryside 1100 brute-force, implementation 1m 25s ✓ C Petya and File System 1800 data-structures, implementation 2m 13s ✓ D Petya and His Friends 1700 constructive-algorithms, math, number-theory...

Practice › Codeforces Solutions › Codeforces Beta Round 79 (Div. 1 Only) ›

CF 101C - Vectors

CF 101C - Vectors Rating: 2000 Tags: implementation, math Solve time: 2m 22s Verified: yes Solution Problem Understanding We start with a vector A = (x1, y1) and want to transform it into another vector B = (x2, y2) . Two operations are allowed. We may rotate the current vector by 90 degrees clockwise, and we may add vector C = (x3, y3) any number of times. The operations may...

Practice › Codeforces Solutions › Codeforces Beta Round 36 ›

CF 36C - Bowls

CF 36C - Bowls Rating: 2200 Tags: geometry, implementation Solve time: 2m 5s Verified: no Solution Problem Understanding Each bowl is a frustum, a cone with its tip cut off. A bowl is described by its height h , bottom radius r , and top radius R . The bowls are stacked in the given order, always sharing the same vertical axis. Every new bowl is lowered as much as...

Practice › Codeforces Solutions › Unknown Language Round 3 ›

CF 100A - Carpeting the Room

CF 100A - Carpeting the Room Rating: 1100 Tags: *special, implementation Solve time: 2m 19s Verified: yes Solution Problem Understanding We have a square room with side length n , so the total area is n × n . We also have k square carpets, each with side length n1 . Every carpet always stays axis-aligned because rotation is forbidden, but since the carpets are squares, rotation would not actually...

Practice › Codeforces Solutions › Codeforces Beta Round 63 (Div. 2) ›

CF 69C - Game

CF 69C - Game Rating: 2000 Tags: implementation Solve time: 2m 15s Verified: yes Solution Problem Understanding Each player owns a multiset of artifacts. Some artifacts are basic and can be purchased directly. Some are composite and can be crafted from several basic artifacts in fixed quantities. Whenever a player buys a basic artifact, it is added to their inventory. Immediately after that purchase, it may become possible to craft...

Practice › Codeforces Solutions › Codeforces Beta Round 89 (Div. 2) ›

CF 118A - String Task

CF 118A - String Task Rating: 1000 Tags: implementation, strings Solve time: 1m 38s Verified: yes Solution Problem Understanding We receive a single string containing uppercase and lowercase English letters. The task is to transform this string according to three rules. First, every vowel must be removed. The vowels in this problem are A, O, Y, E, U, I in both uppercase and lowercase forms. Second, every remaining character is...

Practice › Codeforces Solutions › Codeforces Beta Round 46 (Div. 2) ›

CF 49D - Game

CF 49D - Game Rating: 1800 Tags: brute force, dp, implementation Solve time: 1m 47s Verified: yes Solution Problem Understanding The game is played on a one-dimensional stripe of squares, each either black or white. Vasya paints the initial configuration, and Petya can then perform moves to achieve an alternating pattern, where no two adjacent squares share the same color. A move consists of choosing any two consecutive squares of...

Practice › Codeforces Solutions › Codeforces Beta Round 88 ›

CF 117A - Elevator

CF 117A - Elevator Rating: 1300 Tags: implementation, math Solve time: 2m 31s Verified: yes Solution Problem Understanding The elevator follows a completely deterministic cycle. It starts at floor 1 at time 0 , climbs one floor per second until it reaches floor m , then immediately reverses direction and goes back down to floor 1 , again moving one floor per second. After reaching floor 1 , the same...

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Yandex.Algorithm 2011: Qualification 2

Yandex.Algorithm 2011: Qualification 2 Type: Special | Problems: 5 | Verified: 4/5 | Rating range: 1100-2600 | Time: 11m 32s Problem Name Rating Tags Solve Time Verified A Double Cola 1100 implementation, math 1m 30s ✓ B Sets 1700 constructive-algorithms, hashing, implementation 2m 17s ✗ C General Mobilization 2000 data-structures, dfs-and-similar, sortings 2m 42s ✓ D Two out of Three 2000 dp 2m 57s ✓ E Corridor 2600 geometry 2m...

Practice › Codeforces Solutions › Unknown Language Round 2 ›

CF 72I - Goofy Numbers

CF 72I - Goofy Numbers Rating: 1500 Tags: *special, implementation Solve time: 1m 12s Verified: yes Solution Problem Understanding We are asked to classify a single non-negative integer based on how it relates to its digits. Specifically, each digit of the number is considered as a potential divisor. The integer falls into one of three categories: it is happier if it is divisible by every non-zero digit, happy if it...

Practice › Codeforces Solutions › Codeforces Beta Round 32 (Div. 2, Codeforces format) ›

CF 32B - Borze

CF 32B - Borze Rating: 800 Tags: expression parsing, implementation Solve time: 1m 17s Verified: yes Solution Problem Understanding We are given a string written in the Borze encoding system. Every digit of a ternary number is represented by one of three patterns: "." represents 0 "-." represents 1 "--" represents 2 The task is to decode the entire string and print the resulting ternary number. The key detail is...

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Codeforces Beta Round 96 (Div. 2)

Codeforces Beta Round 96 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 900-1200 | Time: 2m 34s Problem Name Rating Tags Solve Time Verified A HQ9+ 900 implementation 1m 4s ✓ B Unary 1200 implementation 1m 30s ✓

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Codeforces Alpha Round 20 (Codeforces format)

Codeforces Alpha Round 20 (Codeforces format) Type: Special | Problems: 3 | Verified: 3/3 | Rating range: 1700-2000 | Time: 4m 1s Problem Name Rating Tags Solve Time Verified A BerOS file system 1700 implementation 1m 20s ✓ B Equation 2000 math 1m 5s ✓ C Dijkstra? 1900 graphs, shortest-paths 1m 36s ✓

Practice › Codeforces Solutions › Yandex.Algorithm Open 2011: Qualification 1 ›

CF 81B - Sequence Formatting

CF 81B - Sequence Formatting Rating: 1700 Tags: implementation, strings Solve time: 1m 43s Verified: yes Solution Problem Understanding We are given a messy textual representation of a sequence. The string may contain positive integers, commas, spaces, and the special token ... . Spaces may appear in the wrong places or appear multiple times. The task is purely formatting. We must rewrite the string so that every token follows a...

Practice › Codeforces Solutions › Codeforces Beta Round 61 (Div. 2) ›

CF 66A - Petya and Java

CF 66A - Petya and Java Rating: 1300 Tags: implementation, strings Solve time: 1m 33s Verified: yes Solution Problem Understanding We are given a decimal integer as a string. The number can be extremely large, up to 100 digits long, so it may not fit into normal integer types in many programming languages. The task is to determine the smallest Java integer type that can store this value. The available...

Practice › Codeforces Solutions › Codeforces Beta Round 74 (Div. 1 Only) ›

CF 89B - Widget Library

CF 89B - Widget Library Rating: 2300 Tags: dp, expression parsing, graphs, implementation Solve time: 2m 3s Verified: yes Solution Problem Understanding We are asked to simulate a tiny GUI layout system. There are three kinds of widgets. A plain Widget has a fixed width and height. HBox and VBox are container widgets that can store other widgets. An HBox places children horizontally, while a VBox places them vertically. Each...

Practice › Codeforces Solutions › Codeforces Beta Round 44 (Div. 2) ›

CF 47C - Crossword

CF 47C - Crossword Rating: 2000 Tags: implementation Solve time: 2m 32s Verified: no Solution Problem Understanding We are given six words and must arrange them into a very specific crossword shape. The shape looks like a rectangular infinity symbol. There are three horizontal words and three vertical words, and they intersect at fixed positions. The important detail is that the structure is rigid. Once we decide which words are...

Practice › Codeforces Solutions › Codeforces Beta Round 35 (Div. 2) ›

CF 35A - Shell Game

CF 35A - Shell Game Rating: 1000 Tags: implementation Solve time: 1m 26s Verified: yes Solution Problem Understanding We have three cups arranged in a line, and a ball starts under one of them. The performer performs exactly three swaps. Each swap exchanges the positions of two cups. After all swaps finish, we must determine which cup contains the ball. The input first gives the starting cup index, from 1...

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Unknown Language Round 3

Unknown Language Round 3 Type: Special | Problems: 10 | Verified: 10/10 | Rating range: 1100-2400 | Time: 23m 31s Problem Name Rating Tags Solve Time Verified A Carpeting the Room 1100 *special, implementation 2m 19s ✓ B Friendly Numbers 1500 *special, implementation 2m 19s ✓ C A+B 1400 *special, implementation 1m 27s ✓ D World of Mouth 1500 *special, strings 2m 18s ✓ E Lamps in a Line 1600...

Practice › Codeforces Solutions › Codeforces Beta Round 7 ›

CF 7B - Memory Manager

CF 7B - Memory Manager Rating: 1600 Tags: implementation Solve time: 1m 1s Verified: yes Solution Problem Understanding We are asked to implement a simple memory manager for a linear memory array of size m . Each memory cell can either be free or occupied by a block. We are to process a sequence of operations: alloc n , erase x , and defragment . An alloc n request tries...

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Manthan 2011

Manthan 2011 Type: Special | Problems: 5 | Verified: 5/5 | Rating range: 1800-2600 | Time: 9m 26s Problem Name Rating Tags Solve Time Verified A Partial Teacher 1800 dp, graphs, greedy 2m 6s ✓ B Restoration of the Permutation 1800 greedy 1m 59s ✓ C Sequence of Balls 2600 dp 1m 24s ✓ D Optical Experiment 1900 binary-search, data-structures, dp 1m 53s ✓ E Save the City! 2500 geometry...

Practice › Codeforces Solutions › School Team Contest 2 (Winter Computer School 2010/11) ›

CF 44A - Indian Summer

CF 44A - Indian Summer Rating: 900 Tags: implementation Solve time: 1m 23s Verified: yes Solution Problem Understanding Each leaf is described by two strings: the tree species and the leaf color. Alyona only keeps a leaf if she does not already have another leaf with the exact same pair of values. The task is simply to count how many distinct (species, color) combinations appear in the input. If the...

Practice › Codeforces Solutions › School Team Contest 2 (Winter Computer School 2010/11) ›

CF 44G - Shooting Gallery

CF 44G - Shooting Gallery Rating: 2500 Tags: data structures, implementation Solve time: 1m 23s Verified: yes Solution Problem Understanding The problem can be restated as simulating bullets flying along the positive Z axis at given coordinates on a 2D shooting plane ( XOY ). Each bullet may hit one of multiple rectangular targets floating at distinct heights along the Z axis. A target is represented by a rectangle aligned...

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Codeforces Beta Round 10

Codeforces Beta Round 10 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 900-2800 | Time: 8m 3s Problem Name Rating Tags Solve Time Verified A Power Consumption Calculation 900 implementation 1m 30s ✓ B Cinema Cashier 1500 dp, implementation 1m 24s ✓ C Digital Root 2000 number-theory 1m 41s ✓ D LCIS 2800 dp 2m ✗ E Greedy Change 2600 constructive-algorithms 1m 28s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 85 (Div. 2 Only) ›

CF 112A - Petya and Strings

CF 112A - Petya and Strings Rating: 800 Tags: implementation, strings Solve time: 1m 37s Verified: yes Solution Problem Understanding We are given two strings made of English letters. Both strings have the same length, but letters may appear in either uppercase or lowercase form. The task is to compare the two strings lexicographically while completely ignoring letter case. Ignoring case means that 'A' and 'a' must be treated as...

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Codeforces Beta Round 18 (Div. 2 Only)

Codeforces Beta Round 18 (Div. 2 Only) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1200-2000 | Time: 7m 50s Problem Name Rating Tags Solve Time Verified A Triangle 1500 brute-force, geometry 1m 48s ✓ B Platforms 1700 brute-force, math 1m 13s ✓ C Stripe 1200 data-structures, implementation 1m 43s ✓ D Seller Bob 2000 brute-force, dp, greedy 1m 54s ✓ E Flag 2 2000 dp...

Practice › Codeforces Solutions › Codeforces Beta Round 31 (Div. 2, Codeforces format) ›

CF 31D - Chocolate

CF 31D - Chocolate Rating: 2000 Tags: dfs and similar, implementation Solve time: 59s Verified: yes Solution Problem Understanding We are given a rectangular chocolate bar with integer width W and height H . Bob breaks the chocolate multiple times along vertical or horizontal lines that go from one edge to the opposite edge of a piece. Each break is specified by two endpoints, and the set of breaks is...

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Codeforces Beta Round 57 (Div. 2)

Codeforces Beta Round 57 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2000 | Time: 14m 51s Problem Name Rating Tags Solve Time Verified A Ultra-Fast Mathematician 800 implementation 2m 4s ✓ B Hard Work 1300 strings 6m 35s ✓ C Capture Valerian 2000 math 2m 49s ✓ D Eternal Victory 1800 dfs-and-similar, graphs, greedy 1m 29s ✓ E Enemy is weak 1900 data-structures,...

Practice › Codeforces Solutions › Yandex.Algorithm 2011: Finals ›

CF 97A - Domino

CF 97A - Domino Rating: 2400 Tags: brute force, implementation Solve time: 2m 46s Verified: no Solution Problem Understanding We are given a grid of size n × m , representing a board where Gennady has placed 28 domino chips. Each domino occupies exactly two adjacent squares, and the squares of the same domino are marked with the same letter, while different dominoes have different letters. Some squares may be...

Practice › Codeforces Solutions › Yandex.Algorithm 2011: Round 2 ›

CF 86D - Powerful array

CF 86D - Powerful array Rating: 2200 Tags: data structures, implementation, math, two pointers Solve time: 3m 46s Verified: yes Solution Problem Understanding We are given an array of positive integers and many interval queries. For each query [l, r] , we look only at the subarray between those indices and compute a value called its power. If a number x appears k times inside the subarray, then x contributes...

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Codeforces Beta Round 16 (Div. 2 Only)

Codeforces Beta Round 16 (Div. 2 Only) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-1900 | Time: 7m 6s Problem Name Rating Tags Solve Time Verified A Flag 800 implementation 1m 8s ✓ B Burglar and Matches 900 greedy, implementation, sortings 1m 13s ✓ C Monitor 1800 binary-search, number-theory 1m 37s ✓ D Logging 1900 implementation, strings 1m 34s ✓ E Fish 1900 bitmasks, dp,...

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Codeforces Beta Round 39

Codeforces Beta Round 39 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1300-2600 | Time: 7m 51s Problem Name Rating Tags Solve Time Verified A Find Color 1300 constructive-algorithms, geometry, implementation 1m 24s ✓ B Repaintings 1600 math 1m 44s ✓ C Berland Square 2300 implementation, math 1m 38s ✓ D Interesting Sequence 2600 math 1m 55s ✓ E Number Table 2500 combinatorics 1m 10s ✓

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School Team Contest 2 (Winter Computer School 2010/11)

School Team Contest 2 (Winter Computer School 2010/11) Type: Special | Problems: 10 | Verified: 6/10 | Rating range: 900-2700 | Time: 21m 26s Problem Name Rating Tags Solve Time Verified A Indian Summer 900 implementation 1m 23s ✓ B Cola 1500 implementation 1m 9s ✓ C Holidays 1300 implementation 1m 24s ✓ D Hyperdrive 1800 math 1m 5s ✓ E Anfisa the Monkey 1400 dp 2m 13s ✗ F...

Practice › Codeforces Solutions › Codeforces Beta Round 9 (Div. 2 Only) ›

CF 9B - Running Student

CF 9B - Running Student Rating: 1200 Tags: brute force, geometry, implementation Solve time: 1m 26s Verified: yes Solution Problem Understanding The student is already riding a bus that moves along the x-axis from left to right. The bus stops at fixed positions (xi, 0) in increasing order. At any stop except the first one, the student may get off and run directly to the university located at (xu, yu)...

Practice › Codeforces Solutions › School Team Contest 1 (Winter Computer School 2010/11) ›

CF 39G - Inverse Function

CF 39G - Inverse Function Rating: 2400 Tags: implementation Solve time: 2m 2s Verified: yes Solution Problem Understanding We are given the source code of a tiny recursive function f(n) written in a heavily restricted subset of C++. The function only contains sequential if (...) return ...; statements and unconditional return ...; statements. Expressions may contain arithmetic, comparisons, and recursive calls to f . The machine arithmetic is unusual. Addition,...

Practice › Codeforces Solutions › Codeforces Beta Round 15 ›

CF 15D - Map

CF 15D - Map Rating: 2500 Tags: data structures, implementation, sortings Solve time: 2m 12s Verified: yes Solution Problem Understanding We are given a rectangular map of size n × m , where each cell has a non-negative height. Peter wants to build cities of size a × b . To place a city, he must level the ground inside its rectangle by reducing all cells to the minimum height...

Practice › Codeforces Solutions › Codeforces Beta Round 31 (Div. 2, Codeforces format) ›

CF 31A - Worms Evolution

CF 31A - Worms Evolution Rating: 1200 Tags: implementation Solve time: 1m 46s Verified: yes Solution Problem Understanding We are given an array of worm lengths. Each position represents a different worm form, and we need to find three distinct indices such that the length at one index equals the sum of the lengths at the other two indices. More concretely, we want indices i , j , and k...

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Yandex.Algorithm 2011: Round 1

Yandex.Algorithm 2011: Round 1 Type: Special | Problems: 5 | Verified: 5/5 | Rating range: 1300-2600 | Time: 11m 13s Problem Name Rating Tags Solve Time Verified A Domino 1300 constructive-algorithms, implementation 2m 9s ✓ B Embassy Queue 1800 data-structures, greedy 2m 1s ✓ C Petya and Tree 2200 binary-search, dfs-and-similar, probabilities 2m 4s ✓ D Sum of Medians 2300 binary-search, brute-force, data-structures 1m 18s ✓ E Guard Towers 2600...

Practice › Codeforces Solutions › Codeforces Beta Round 39 ›

CF 40A - Find Color

CF 40A - Find Color Rating: 1300 Tags: constructive algorithms, geometry, implementation, math Solve time: 1m 24s Verified: yes Solution Problem Understanding The plane is colored using concentric rings centered at the origin. Every ring between two consecutive integer distances alternates color. The borders themselves, meaning all points whose distance from the origin is an integer, are always black. For a point (x, y) , we need to determine whether...

Practice › Codeforces Solutions › Codeforces Beta Round 19 ›

CF 19A - World Football Cup

CF 19A - World Football Cup Rating: 1400 Tags: implementation Solve time: 5m 51s Verified: yes Solution Problem Understanding We are given the full results of a football tournament where every pair of teams plays exactly one match. For each match, we know how many goals each side scored. Using the tournament rules, we must determine which teams advance to the knockout stage. Each team earns points from matches. A...

Practice › Codeforces Solutions › Unknown Language Round 4 ›

CF 130A - Hexagonal numbers

CF 130A - Hexagonal numbers Rating: 900 Tags: *special, implementation Solve time: 1m 24s Verified: yes Solution Problem Understanding We need to compute the $n$-th hexagonal number. The sequence is defined by the formula $$h_n = 2n^2 - n$$ The input contains a single integer $n$, and the output is the value produced by this formula. For example, when $n = 2$, $$h_2 = 2 \cdot 2^2 - 2 =...

Practice › Codeforces Solutions › Codeforces Beta Round 52 (Div. 2) ›

CF 56B - Spoilt Permutation

CF 56B - Spoilt Permutation Rating: 1300 Tags: implementation Solve time: 1m 42s Verified: yes Solution Problem Understanding We start from the sorted permutation 1 2 3 ... n . Someone chooses exactly one contiguous segment and reverses it. We are given the final permutation and must determine whether it could have been produced by exactly one such reversal. The task is not to sort the array. We only need...

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Yandex.Algorithm Open 2011: Qualification 1

Yandex.Algorithm Open 2011: Qualification 1 Type: Special | Problems: 5 | Verified: 3/5 | Rating range: 1400-2700 | Time: 13m 8s Problem Name Rating Tags Solve Time Verified A Plug-in 1400 implementation 1m 36s ✓ B Sequence Formatting 1700 implementation, strings 1m 43s ✓ C Average Score 1700 greedy, math, sortings 3m 31s ✓ D Polycarp's Picture Gallery 2100 constructive-algorithms, greedy 2m 48s ✗ E Pairs 2700 dfs-and-similar, dp, dsu...

Practice › Codeforces Solutions › Codeforces Beta Round 52 (Div. 2) ›

CF 56C - Corporation Mail

CF 56C - Corporation Mail Rating: 1700 Tags: data structures, expression parsing, implementation Solve time: 1m 33s Verified: yes Solution Problem Understanding The problem presents a company hierarchy encoded as a string. Each employee has a name, followed optionally by a colon and a comma-separated list of subordinates, ending with a dot. If an employee has no subordinates, the colon is omitted. Multiple employees can have the same name. The...

Practice › Codeforces Solutions › Codeforces Beta Round 67 (Div. 2) ›

CF 75B - Facetook Priority Wall

CF 75B - Facetook Priority Wall Rating: 1500 Tags: expression parsing, implementation, strings Solve time: 2m 14s Verified: no Solution Problem Understanding We are given the name of a user on a social network and a sequence of activity messages between users. Every activity contributes a certain number of points between the two people involved. The three possible activities are: posting on someone's wall, worth 15 points commenting on someone's...

Practice › Codeforces Solutions › Codeforces Beta Round 16 (Div. 2 Only) ›

CF 16D - Logging

CF 16D - Logging Rating: 1900 Tags: implementation, strings Solve time: 1m 34s Verified: yes Solution Problem Understanding We are given a sequence of log entries in the exact order they were written. Originally every entry had both a date and a time, but the dates were lost, so only the 12-hour clock timestamps remain. The task is to reconstruct the smallest possible number of distinct days that could produce...

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Codeforces Beta Round 92 (Div. 2 Only)

Codeforces Beta Round 92 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1400 | Time: 3m 1s Problem Name Rating Tags Solve Time Verified A The number of positions 1000 math 1m 27s ✓ B Permutations 1400 brute-force, combinatorics, implementation 1m 34s ✓

Practice › Codeforces Solutions › Codeforces Round 933 (Div. 3) ›

CF 1941D - Rudolf and the Ball Game

CF 1941D - Rudolf and the Ball Game Rating: 1200 Tags: dfs and similar, dp, implementation Solve time: 1m 17s Verified: no Solution Problem Understanding We have a circle of n players, numbered 1 through n clockwise. The ball starts with player x . There are m throws, and each throw has a distance r_i and a remembered direction c_i . The direction could be clockwise ( 0 ), counterclockwise...

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Codeforces Beta Round 11

Codeforces Beta Round 11 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 900-2800 | Time: 8m 46s Problem Name Rating Tags Solve Time Verified A Increasing Sequence 900 constructive-algorithms, implementation, math 1m 24s ✓ B Jumping Jack 1600 math 1m 26s ✓ C How Many Squares? 2200 implementation 2m 42s ✓ D A Simple Task 2200 bitmasks, dp, graphs 1m 29s ✓ E Forward, march! 2800 binary-search,...

Practice › Codeforces Solutions › Codeforces Beta Round 74 (Div. 1 Only) ›

CF 89C - Chip Play

CF 89C - Chip Play Rating: 2300 Tags: brute force, data structures, implementation Solve time: 2m 14s Verified: yes Solution Problem Understanding We have a grid containing chips. Every chip stores one direction, left, right, up, or down. When we start a move from some chip, the process behaves like this: The current chip looks in the direction of its arrow. Among all remaining chips in that row or column,...

Practice › Codeforces Solutions › Codeforces Beta Round 55 (Div. 2) ›

CF 59D - Team Arrangement

CF 59D - Team Arrangement Rating: 2000 Tags: constructive algorithms, greedy, implementation Solve time: 2m 39s Verified: no Solution Problem Understanding We have 3n students ranked by personal performance. Higher-ranked students become captains earlier. When a captain forms a team, they choose two currently unassigned students according to their personal preference list. The final teams are already known, and the teams are listed in the exact order they were created....

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School Regional Team Contest, Saratov, 2011

School Regional Team Contest, Saratov, 2011 Type: Special | Problems: 10 | Verified: 8/10 | Rating range: 1000-2200 | Time: 16m 31s Problem Name Rating Tags Solve Time Verified A Elevator 1000 brute-force, implementation, math 1m 26s ✓ B Quiz League 1100 implementation 1m 21s ✓ C Winnie-the-Pooh and honey 1100 implementation, math 1m 39s ✓ D Three Sons 1400 brute-force 1m 35s ✓ E Put Knight! 1400 games, math...

Practice › Codeforces Solutions › Codeforces Beta Round 12 (Div 2 Only) ›

CF 12B - Correct Solution?

CF 12B - Correct Solution? Rating: 1100 Tags: implementation, sortings Solve time: 1m 19s Verified: yes Solution Problem Understanding Alice gives Bob a decimal number and asks him to rearrange its digits so that the resulting number is as small as possible, while still being a valid decimal number without leading zeroes. Bob returns another number, and we must decide whether his answer is actually the smallest possible arrangement. The...

Practice › Codeforces Solutions › Codeforces Beta Round 97 (Div. 1) ›

CF 135D - Cycle

CF 135D - Cycle Rating: 2500 Tags: brute force, dfs and similar, implementation Solve time: 1m 50s Verified: yes Solution Problem Understanding We are given a binary grid. Cells containing '1' form usable tiles, while '0' cells are blocked. We want the longest cycle made entirely from '1' cells. The cycle must behave like a simple closed curve on the grid. Every cell on the cycle must touch exactly two...

Practice › Codeforces Solutions › School Regional Team Contest, Saratov, 2011 ›

CF 120B - Quiz League

CF 120B - Quiz League Rating: 1100 Tags: implementation Solve time: 1m 21s Verified: yes Solution Problem Understanding We are given a circular table divided into n sectors, each containing a quiz question. Some questions have already been asked, marked with a 0 , and others are still available, marked with a 1 . An arrow points at sector k , and the goal is to determine the number of...

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Codeforces Beta Round 90

Codeforces Beta Round 90 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 800-2500 | Time: 9m 34s Problem Name Rating Tags Solve Time Verified A Epic Game 800 implementation 1m 29s ✓ B Before Exam 1900 constructive-algorithms, implementation, sortings 2m 2s ✓ C Education Reform 2000 dp 2m 59s ✗ D String Transformation 2500 hashing, strings 1m 34s ✓ E Alternative Reality 2400 geometry 1m 30s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 34 (Div. 2) ›

CF 34A - Reconnaissance 2

CF 34A - Reconnaissance 2 Rating: 800 Tags: implementation Solve time: 1m 18s Verified: yes Solution Problem Understanding We are given the heights of soldiers standing in a circle. Two soldiers can form a reconnaissance unit if they stand next to each other and their height difference is as small as possible among all neighboring pairs. The circular arrangement changes one important detail. The first and last soldiers are also...

Practice › Codeforces Solutions › Yandex.Algorithm Open 2011: Qualification 1 ›

CF 81A - Plug-in

CF 81A - Plug-in Rating: 1400 Tags: implementation Solve time: 1m 36s Verified: yes Solution Problem Understanding We are given a lowercase string that may contain accidental repeated keystrokes. Whenever two equal characters become adjacent, both characters must be deleted. After removing one pair, new adjacent equal pairs may appear, and those must also be removed. The process continues until no adjacent equal characters remain. The final remaining string must...

Practice › Codeforces Solutions › Codeforces Testing Round 1 ›

CF 52A - 123-sequence

CF 52A - 123-sequence Rating: 900 Tags: implementation Solve time: 1m 38s Verified: yes Solution Problem Understanding We are given a list of integers where every number is either 1, 2, or 3. The goal is to transform the sequence so that all numbers are the same, and we want to do this using the smallest number of replacements possible. Each replacement consists of changing a number to any of...

Practice › Codeforces Solutions › Codeforces Beta Round 69 (Div. 1 Only) ›

CF 77A - Heroes

CF 77A - Heroes Rating: 1400 Tags: brute force, implementation Solve time: 1m 49s Verified: yes Solution Problem Understanding We have exactly seven heroes and three bosses. Each boss gives some amount of experience, and every hero assigned to that boss receives an equal share rounded down. If a boss gives x experience and its team has k heroes, then every hero in that team receives x // k ....

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Codeforces Beta Round 49 (Div. 2)

Codeforces Beta Round 49 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1100-2500 | Time: 13m 28s Problem Name Rating Tags Solve Time Verified A Autocomplete 1100 implementation 3m 28s ✓ B Blog Photo 1700 binary-search, implementation 2m 21s ✓ C Little Frog 1200 constructive-algorithms 1m 35s ✓ D Physical Education 1500 sortings 2m 6s ✓ E Dead Ends 2500 bitmasks, dp 3m 58s...

Practice › Codeforces Solutions › Codeforces Beta Round 32 (Div. 2, Codeforces format) ›

CF 32E - Hide-and-Seek

CF 32E - Hide-and-Seek Rating: 2400 Tags: geometry, implementation Solve time: 2m 25s Verified: yes Solution Problem Understanding We have two people represented as points on the plane, Victor and Peter. The room contains exactly two objects, a solid wall segment and a double-sided mirror segment. Victor wants to know whether he can see Peter either directly or through a single reflection in the mirror. A direct line of sight...

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Codeforces Beta Round 78 (Div. 1 Only)

Codeforces Beta Round 78 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1700-2700 | Time: 10m 13s Problem Name Rating Tags Solve Time Verified A Help Victoria the Wise 1700 brute-force, implementation 2m 12s ✓ B Help King 2200 implementation, probabilities, trees 1m 17s ✓ C Help Greg the Dwarf 2500 geometry, ternary-search 2m 29s ✓ D Help Monks 2500 constructive-algorithms 1m 50s...

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Codeforces Beta Round 98 (Div. 2)

Codeforces Beta Round 98 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 900-2000 | Time: 7m 45s Problem Name Rating Tags Solve Time Verified A Postcards and photos 900 implementation 1m 28s ✓ B Permutation 1000 greedy 1m 13s ✓ C History 1500 sortings 1m 36s ✓ D Palindromes 1900 dp, strings 2m 9s ✓ E Last Chance 2000 data-structures, implementation, strings 1m 19s...

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Codeforces Beta Round 24

Codeforces Beta Round 24 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1400-2400 | Time: 11m 12s Problem Name Rating Tags Solve Time Verified A Ring road 1400 graphs 3m 36s ✓ B F1 Champions 1500 implementation 2m 19s ✓ C Sequence of points 1800 geometry, implementation, math 2m 35s ✓ D Broken robot 2400 dp, math, probabilities 1m 34s ✓ E Berland collider 2300 binary-search 1m...

Practice › Codeforces Solutions › Codeforces Beta Round 30 (Codeforces format) ›

CF 30B - Codeforces World Finals

CF 30B - Codeforces World Finals Rating: 1700 Tags: implementation Solve time: 1m 1s Verified: yes Solution Problem Understanding We are given two dates in the format DD.MM.YY : one representing the day of the Codeforces World Finals and the other representing Bob's date of birth. Bob can rearrange the components of his birth date-the day, month, and year-but only as complete numbers, not individual digits. The goal is to...

Practice › Codeforces Solutions ›

Codeforces Beta Round 86 (Div. 1 Only)

Codeforces Beta Round 86 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1600-2700 | Time: 15m 15s Problem Name Rating Tags Solve Time Verified A Grammar Lessons 1600 implementation, strings 4m 41s ✓ B Petr# 2000 brute-force, data-structures, hashing 3m 20s ✓ C Double Happiness 2200 brute-force, math, number-theory 3m 20s ✓ D Museum 2700 math, matrices, probabilities 1m 55s ✓ E Sleeping...

Practice › Codeforces Solutions › Codeforces Beta Round 35 (Div. 2) ›

CF 35B - Warehouse

CF 35B - Warehouse Rating: 1700 Tags: implementation Solve time: 1m 21s Verified: yes Solution Problem Understanding We are asked to simulate a warehouse with a grid-like shelving system. Each shelf has m sections, and there are n shelves stacked from top to bottom. Every section can hold at most one box. We receive a sequence of operations: some add boxes to a given shelf and section, and others remove...

Practice › Codeforces Solutions › Codeforces Beta Round 76 (Div. 1 Only) ›

CF 93C - Azembler

CF 93C - Azembler Rating: 2500 Tags: brute force, implementation Solve time: 2m 1s Verified: yes Solution Problem Understanding We start with one register, eax , containing some unknown value x . Every other register contains 0 . The goal is to produce n * x in any register using the minimum possible number of lea instructions. The instruction set is surprisingly limited, but also surprisingly powerful. A single lea...

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Codeforces Beta Round 5

Codeforces Beta Round 5 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1000-2400 | Time: 5m 59s Problem Name Rating Tags Solve Time Verified A Chat Servers Outgoing Traffic 1000 implementation 1m 9s ✓ B Center Alignment 1200 implementation, strings 1m 24s ✓ C Longest Regular Bracket Sequence 1900 constructive-algorithms, data-structures, dp 1m 21s ✓ D Follow Traffic Rules 2100 implementation, math 54s ✓ E Bindian Signalizing...

Practice › Codeforces Solutions › Codeforces Beta Round 56 ›

CF 60A - Where Are My Flakes?

CF 60A - Where Are My Flakes? Rating: 1300 Tags: implementation, two pointers Solve time: 1m 40s Verified: yes Solution Problem Understanding There are n boxes arranged in a straight line. Exactly one of them may contain the cereal flakes. The roommate leaves statements of two possible forms. If the hint says "To the left of i" , then the flakes must be somewhere strictly before box i . Box...

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Codeforces Beta Round 75 (Div. 2 Only)

Codeforces Beta Round 75 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1300 | Time: 4m 34s Problem Name Rating Tags Solve Time Verified A Chips 800 implementation, math 3m 15s ✓ B Binary Number 1300 greedy 1m 19s ✓

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Codeforces Beta Round 84 (Div. 1 Only)

Codeforces Beta Round 84 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1000-2700 | Time: 11m 6s Problem Name Rating Tags Solve Time Verified A Lucky Sum of Digits 1000 brute-force, implementation 2m 22s ✓ B Lucky Probability 1900 brute-force, probabilities 2m 23s ✓ C Lucky Tree 1900 dp, dsu, trees 2m 23s ✓ D Lucky Sorting 2000 constructive-algorithms, sortings 1m 47s ✓...

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Codeforces Beta Round 12 (Div 2 Only)

Codeforces Beta Round 12 (Div 2 Only) Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 800-2400 | Time: 6m 41s Problem Name Rating Tags Solve Time Verified A Super Agent 800 implementation 1m 15s ✓ B Correct Solution? 1100 implementation, sortings 1m 19s ✓ C Fruits 1100 greedy, implementation, sortings 1m 2s ✓ D Ball 2400 data-structures, sortings 1m 52s ✓ E Start of the session 2100...

Practice › Codeforces Solutions › Codeforces Beta Round 33 (Codeforces format) ›

CF 33A - What is for dinner?

CF 33A - What is for dinner? Rating: 1200 Tags: greedy, implementation Solve time: 3m 53s Verified: yes Solution Problem Understanding Each tooth belongs to exactly one row. When Valerie eats one crucian using a row, every tooth in that row loses one unit of viability. A row becomes unusable as soon as at least one tooth inside it would drop below zero. For a single row, the limiting factor...

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Codeforces Beta Round 71

Codeforces Beta Round 71 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1200-2900 | Time: 7m 45s Problem Name Rating Tags Solve Time Verified A Bus Game 1200 greedy 1m 20s ✓ B Colorful Field 1400 implementation, sortings 1m 19s ✓ C Beaver 1800 data-structures, dp, greedy 1m 27s ✓ D Password 2800 bitmasks, dp, shortest-paths 2m 11s ✓ E Security System 2900 math 1m 28s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 84 (Div. 1 Only) ›

CF 109A - Lucky Sum of Digits

CF 109A - Lucky Sum of Digits Rating: 1000 Tags: brute force, implementation Solve time: 2m 22s Verified: yes Solution Problem Understanding We need to construct the smallest possible lucky number whose digits add up to a given value n . A lucky number may contain only digits 4 and 7 . For example, 447 is valid because every digit is either 4 or 7 , while 45 is invalid...

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Codeforces Beta Round 88

Codeforces Beta Round 88 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1300-2900 | Time: 13m 35s Problem Name Rating Tags Solve Time Verified A Elevator 1300 implementation, math 2m 31s ✓ B Very Interesting Game 1800 brute-force, number-theory 2m 31s ✓ C Cycle 2000 dfs-and-similar, graphs 3m ✓ D Not Quick Transformation 2500 divide-and-conquer, math 2m 20s ✓ E Tree or not Tree 2900 data-structures, divide-and-conquer,...

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Codeforces Beta Round 1

Codeforces Beta Round 1 Type: Beta | Problems: 3 | Verified: 3/3 | Rating range: 1000-2100 | Time: 10m 36s Problem Name Rating Tags Solve Time Verified A Theatre Square 1000 math 4m 1s ✓ B Spreadsheet 1600 implementation, math 4m 55s ✓ C Ancient Berland Circus 2100 geometry, math 1m 40s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 12 (Div 2 Only) ›

CF 12C - Fruits

CF 12C - Fruits Rating: 1100 Tags: greedy, implementation, sortings Solve time: 1m 2s Verified: yes Solution Problem Understanding Valera has a shopping list containing a number of fruits, possibly with duplicates if he wants more than one of the same type. At the market, the stall has n types of fruits and n price tags, but the tags are not yet attached to the fruits. Each tag represents the...

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Codeforces Beta Round 69 (Div. 1 Only)

Codeforces Beta Round 69 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 2/5 | Rating range: 1400-2800 | Time: 11m 16s Problem Name Rating Tags Solve Time Verified A Heroes 1400 brute-force, implementation 1m 49s ✓ B Falling Anvils 1800 math, probabilities 2m 36s ✓ C Beavermuncher-0xFF 2100 dfs-and-similar, dp, dsu 2m 30s ✗ D Domino Carpet 2300 dp, implementation 1m 59s ✗ E Martian Food 2800...

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Codeforces Beta Round 94 (Div. 1 Only)

Codeforces Beta Round 94 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1500-2900 | Time: 8m 36s Problem Name Rating Tags Solve Time Verified A Statues 1500 dfs-and-similar 2m 10s ✓ B String 2100 brute-force, constructive-algorithms, hashing 1m 21s ✓ C Games with Rectangle 2000 combinatorics, dp 1m 52s ✓ D Numbers 2000 constructive-algorithms, implementation 1m 38s ✓ E Birthday 2900 geometry, math...

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Codeforces Beta Round 95 (Div. 2)

Codeforces Beta Round 95 (Div. 2) Type: Div. 2 | Problems: 6 | Verified: 5/6 | Rating range: 1000-2000 | Time: 10m 6s Problem Name Rating Tags Solve Time Verified A cAPS lOCK 1000 implementation, strings 1m 16s ✓ B Opposites Attract 1200 implementation, math 1m 34s ✓ C The World is a Theatre 1400 combinatorics, math 1m 35s ✓ D Subway 1600 dfs-and-similar, graphs 1m 14s ✓ E Yet...

Practice › Codeforces Solutions › Codeforces Beta Round 73 (Div. 1 Only) ›

CF 87A - Trains

CF 87A - Trains Rating: 1500 Tags: implementation, math Solve time: 1m 15s Verified: yes Solution Problem Understanding Vasya is at the central station of a subway branch with two endpoints. Each endpoint corresponds to one of his girlfriends: Dasha or Masha. Trains to Dasha’s station arrive every a minutes and trains to Masha’s station arrive every b minutes. Vasya arrives at the station at a random moment and always...

Practice › Codeforces Solutions › Codeforces Beta Round 59 (Div. 2) ›

CF 63A - Sinking Ship

CF 63A - Sinking Ship Rating: 900 Tags: implementation, sortings, strings Solve time: 1m 31s Verified: yes Solution Problem Understanding We are given a list of people standing in a fixed left-to-right order on a sinking ship. Every person has a name and a role. The evacuation order depends entirely on the role priority. Rats leave first. Women and children share the next priority level. Men leave after them. The...

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Codeforces Beta Round 80 (Div. 1 Only)

Codeforces Beta Round 80 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1100-2900 | Time: 10m 20s Problem Name Rating Tags Solve Time Verified A Testing Pants for Sadness 1100 greedy, implementation, math 1m 39s ✓ B Cthulhu 1500 dfs-and-similar, dsu, graphs 1m 43s ✓ C Russian Roulette 1900 constructive-algorithms, greedy 2m ✓ D Time to Raid Cowavans 2100 brute-force, data-structures, sortings 1m...

Practice › Codeforces Solutions › Codeforces Beta Round 14 (Div. 2) ›

CF 14B - Young Photographer

CF 14B - Young Photographer Rating: 1000 Tags: implementation Solve time: 1m 20s Verified: yes Solution Problem Understanding The problem asks us to determine how far Bob, a photographer, must move along a straight racetrack to take pictures of every sportsman. Each sportsman runs back and forth along a fixed segment of the racetrack, defined by two positions ai and bi . Bob starts at position x0 , and he...

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Codeforces Beta Round 9 (Div. 2 Only)

Codeforces Beta Round 9 (Div. 2 Only) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2300 | Time: 8m 20s Problem Name Rating Tags Solve Time Verified A Die Roll 800 math, probabilities 2m 43s ✓ B Running Student 1200 brute-force, geometry, implementation 1m 26s ✓ C Hexadecimal's Numbers 1200 brute-force, implementation, math 1m 10s ✓ D How many trees? 1900 combinatorics, divide-and-conquer, dp 1m 13s...

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Codeforces Beta Round 6 (Div. 2 Only)

Codeforces Beta Round 6 (Div. 2 Only) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 900-2600 | Time: 7m 21s Problem Name Rating Tags Solve Time Verified A Triangle 900 brute-force, geometry 1m 18s ✓ B President's Office 1100 implementation 1m 18s ✓ C Alice, Bob and Chocolate 1200 greedy, two-pointers 1m 29s ✓ D Lizards and Basements 2 2600 brute-force, dp 2m 18s ✓ E...

Practice › Codeforces Solutions › Codeforces Beta Round 64 ›

CF 70E - Information Reform

CF 70E - Information Reform Rating: 2700 Tags: dp, implementation, trees Solve time: 3m 29s Verified: no Solution Problem Understanding We are given a country with cities connected by roads such that the road network forms a tree: there is exactly one simple path between any two cities. Each road has equal length in terms of counting the number of edges. The government wants to establish regional centers in some...

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Codeforces Beta Round 42 (Div. 2)

Codeforces Beta Round 42 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1000-2300 | Time: 9m 18s Problem Name Rating Tags Solve Time Verified A Football 1000 strings 1m 29s ✓ B Letter 1100 implementation, strings 1m 31s ✓ C Lucky Tickets 1300 greedy 1m 12s ✓ D Journey 2000 brute-force, constructive-algorithms, implementation 1m 39s ✓ E Race 2300 brute-force, implementation, two-pointers 3m 27s...

Practice › Codeforces Solutions › All-Ukrainian School Olympiad in Informatics ›

CF 76E - Points

CF 76E - Points Rating: 1700 Tags: implementation, math Solve time: 1m 53s Verified: yes Solution Problem Understanding We are given up to one hundred thousand points on a 2D plane. For every unordered pair of points, we must compute the squared Euclidean distance between them and add all those values together. For two points (x1, y1) and (x2, y2) , the squared distance is $(x_1-x_2)^2 + (y_1-y_2)^2$ The task...

Practice › Codeforces Solutions › Codeforces Beta Round 11 ›

CF 11C - How Many Squares?

CF 11C - How Many Squares? Rating: 2200 Tags: implementation Solve time: 2m 42s Verified: yes Solution Problem Understanding We are given a binary grid. A valid object is not a filled square, it is only the border of a square drawn with 1 s. Every cell not belonging to the border must be 0 . The problem asks us to count two kinds of squares. The first kind is...

Practice › Codeforces Solutions › Codeforces Beta Round 57 (Div. 2) ›

CF 61A - Ultra-Fast Mathematician

CF 61A - Ultra-Fast Mathematician Rating: 800 Tags: implementation Solve time: 2m 4s Verified: yes Solution Problem Understanding We are given two binary strings of equal length. Each character is either '0' or '1' . For every position, we compare the characters from the two strings. If the two characters are different, the resulting string gets '1' at that position. If they are the same, the resulting string gets '0'...

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Codeforces Beta Round 74 (Div. 1 Only)

Codeforces Beta Round 74 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1800-2900 | Time: 12m 50s Problem Name Rating Tags Solve Time Verified A Robbery 1800 greedy 1m 54s ✓ B Widget Library 2300 dp, expression-parsing, graphs 2m 3s ✓ C Chip Play 2300 brute-force, data-structures, implementation 2m 14s ✓ D Space mines 2500 geometry 4m 9s ✓ E Fire and Ice...

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Codeforces Beta Round 30 (Codeforces format)

Codeforces Beta Round 30 (Codeforces format) Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1400-2800 | Time: 7m 26s Problem Name Rating Tags Solve Time Verified A Accounting 1400 brute-force, math 1m 23s ✓ B Codeforces World Finals 1700 implementation 1m 1s ✓ C Shooting Gallery 1800 dp, probabilities 1m ✓ D King's Problem? 2600 geometry, greedy 2m 12s ✗ E Tricky and Clever Password 2800 binary-search,...

Practice › Codeforces Solutions › Yandex.Algorithm 2011: Qualification 2 ›

CF 82B - Sets

CF 82B - Sets Rating: 1700 Tags: constructive algorithms, hashing, implementation Solve time: 2m 17s Verified: no Solution Problem Understanding We are given all pairwise unions of some hidden disjoint sets. The original sets themselves are not shown. Suppose the hidden sets are $S_1, S_2, \dots, S_n$. For every pair $i \neq j$, we are given the set $S_i \cup S_j$. These unions are shuffled, so we do not know...

Practice › Codeforces Solutions › Codeforces Beta Round 94 (Div. 2 Only) ›

CF 129B - Students and Shoelaces

CF 129B - Students and Shoelaces Rating: 1200 Tags: brute force, dfs and similar, graphs, implementation Solve time: 2m 15s Verified: yes Solution Problem Understanding We can model the students and shoelaces as an undirected graph. Each student is a vertex, and every shoelace between two students is an edge. In one round, every student whose degree is exactly 1 gets removed at the same time. When those students leave,...

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CF 3C - Tic-tac-toe

CF 3C - Tic-tac-toe Rating: 1800 Tags: brute force, games, implementation Solve time: 4m 37s Verified: yes Problem Understanding We are given a snapshot of a tic-tac-toe board, represented as a 3×3 grid. Each cell is either empty ( . ), contains a cross ( X ), or contains a nought ( 0 ). The first player always places crosses, and the second player places noughts. The board might be...

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Codeforces Beta Round 51

Codeforces Beta Round 51 Type: Beta | Problems: 5 | Verified: 3/5 | Rating range: 1200-2500 | Time: 10m 12s Problem Name Rating Tags Solve Time Verified A Flea travel 1200 implementation, math 1m 24s ✓ B Smallest number 1600 brute-force 1m 47s ✓ C Pie or die 1900 games 1m 43s ✓ D Beautiful numbers 2500 dp, number-theory 3m 29s ✗ E Very simple problem 2500 geometry, two-pointers 1m...

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Codeforces Beta Round 59 (Div. 2)

Codeforces Beta Round 59 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 900-2000 | Time: 8m 47s Problem Name Rating Tags Solve Time Verified A Sinking Ship 900 implementation, sortings, strings 1m 31s ✓ B Settlers' Training 1200 implementation 1m 35s ✓ C Bulls and Cows 1700 brute-force, implementation 1m 48s ✓ D Dividing Island 1900 constructive-algorithms 1m 40s ✗ E Sweets Game 2000...

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Codeforces Alpha Round 21 (Codeforces format)

Codeforces Alpha Round 21 (Codeforces format) Type: Special | Problems: 4 | Verified: 3/4 | Rating range: 1900-2400 | Time: 5m 6s Problem Name Rating Tags Solve Time Verified A Jabber ID 1900 implementation, strings 1m 37s ✗ B Intersection 2000 implementation, math 1m 21s ✓ C Stripe 2 2000 binary-search, dp, sortings 1m 26s ✓ D Traveling Graph 2400 bitmasks, graph-matchings, graphs 42s ✓

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Codeforces Beta Round 60

Codeforces Beta Round 60 Type: Beta | Problems: 5 | Verified: 3/5 | Rating range: 1700-2900 | Time: 11m 31s Problem Name Rating Tags Solve Time Verified A Harry Potter and Three Spells 1800 implementation, math 2m 2s ✓ B Harry Potter and the History of Magic 1700 brute-force, greedy, implementation 2m 33s ✗ C Harry Potter and the Golden Snitch 2100 binary-search, geometry 2m 11s ✓ D Harry Potter...

Practice › Codeforces Solutions › Codeforces Beta Round 89 (Div. 2) ›

CF 118B - Present from Lena

CF 118B - Present from Lena Rating: 1000 Tags: constructive algorithms, implementation Solve time: 1m 42s Verified: yes Solution Problem Understanding We need to print a symmetric diamond made from numbers. The middle row contains numbers increasing from 0 up to n , then decreasing back to 0 . Every row above and below follows the same pattern with a smaller maximum value. For example, when n = 3 ,...

Practice › Codeforces Solutions › School Personal Contest #1 (Winter Computer School 2010/11) - Codeforces Beta Round 38 (ACM-ICPC Rules) ›

CF 38D - Vasya the Architect

CF 38D - Vasya the Architect Rating: 1900 Tags: implementation Solve time: 1m 38s Verified: yes Solution Problem Understanding We stack cubes one by one. Every cube is axis-aligned, and its projection on the ground is a square. Since the cubes are actual cubes, the side length is determined by the square base. Cube i is placed directly on top of cube i-1 . Their projections overlap with positive area,...

Practice › Codeforces Solutions › Codeforces Beta Round 90 ›

CF 119A - Epic Game

CF 119A - Epic Game Rating: 800 Tags: implementation Solve time: 1m 29s Verified: yes Solution Problem Understanding We are asked to simulate a turn-based game between two players, Simon and Antisimon, who each have a fixed integer, a and b respectively. There is a heap of n stones. Players alternate turns starting with Simon, and on a turn, a player must take a number of stones equal to the...

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Codeforces Beta Round 15

Codeforces Beta Round 15 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1200-2600 | Time: 11m 13s Problem Name Rating Tags Solve Time Verified A Cottage Village 1200 implementation, sortings 2m 21s ✓ B Laser 1800 math 2m 54s ✓ C Industrial Nim 2000 games 2m 25s ✓ D Map 2500 data-structures, implementation, sortings 2m 12s ✓ E Triangles 2600 combinatorics, dp 1m 21s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 50 ›

CF 54B - Cutting Jigsaw Puzzle

CF 54B - Cutting Jigsaw Puzzle Rating: 1800 Tags: hashing, implementation Solve time: 1m 29s Verified: yes Solution Problem Understanding We are given a rectangular picture represented as an A × B grid of letters. The task is to determine how many ways we can cut this picture into smaller rectangular pieces such that each piece is unique up to rotations, and to identify the smallest possible piece size among...

Practice › Codeforces Solutions › Codeforces Beta Round 59 (Div. 2) ›

CF 63C - Bulls and Cows

CF 63C - Bulls and Cows Rating: 1700 Tags: brute force, implementation Solve time: 1m 48s Verified: yes Solution Problem Understanding We are playing the classic Bulls and Cows game with four-digit numbers whose digits are all distinct. Leading zeroes are allowed, so 0123 is valid, but repeated digits such as 0012 or 1223 are not. Each previous guess comes with two values. A bull means a digit matches both...

Practice › Codeforces Solutions › Codeforces Beta Round 92 (Div. 1 Only) ›

CF 123A - Prime Permutation

CF 123A - Prime Permutation Rating: 1300 Tags: implementation, number theory, strings Solve time: 2m 19s Verified: no Solution Problem Understanding We are given a string s composed of lowercase letters, with length n . The task is to determine if we can rearrange the letters so that for every prime p less than or equal to n , all positions in the string that are multiples of p can...

Practice › Codeforces Solutions › Codeforces Beta Round 78 (Div. 2 Only) ›

CF 99B - Help Chef Gerasim

CF 99B - Help Chef Gerasim Rating: 1300 Tags: implementation, sortings Solve time: 1m 20s Verified: yes Solution Problem Understanding We are given a set of cups, each containing some amount of juice, and we want to determine whether the volumes could result from the pages pouring juice from one cup to another exactly once, or not at all. Each pouring involves a fixed integer number of milliliters transferred from...

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Codeforces Beta Round 89 (Div. 2)

Codeforces Beta Round 89 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1000-2000 | Time: 10m 4s Problem Name Rating Tags Solve Time Verified A String Task 1000 implementation, strings 1m 38s ✓ B Present from Lena 1000 constructive-algorithms, implementation 1m 42s ✓ C Fancy Number 1900 brute-force, greedy, sortings 2m 51s ✓ D Caesar's Legions 1700 dp 1m 37s ✓ E Bertown roads...

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Codeforces Beta Round 82 (Div. 2)

Codeforces Beta Round 82 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1000-2100 | Time: 13m 18s Problem Name Rating Tags Solve Time Verified A Card Game 1000 implementation 1m 37s ✓ B Choosing Laptop 1000 brute-force, implementation 2m 3s ✓ C Buns 1700 dp 1m 50s ✓ D Treasure Island 1700 brute-force, implementation 2m 25s ✓ E Space Rescuers 2100 geometry, ternary-search 5m...

Practice › Codeforces Solutions › Codeforces Beta Round 40 (Div. 2) ›

CF 41C - Email address

CF 41C - Email address Rating: 1300 Tags: expression parsing, implementation Solve time: 1m 41s Verified: no Solution Problem Understanding We are given a string representing an email address, but all the . symbols have been spelled out as dot and all the @ symbols as at . Our goal is to reconstruct the original, valid email address in its shortest form. If there are multiple candidates with the same...

Practice › Codeforces Solutions › Codeforces Beta Round 15 ›

CF 15A - Cottage Village

CF 15A - Cottage Village Rating: 1200 Tags: implementation, sortings Solve time: 2m 21s Verified: yes Solution Problem Understanding We are given a one-dimensional map of a village where all the houses lie along the x -axis. Each house is square, specified by its center coordinate and its side length. No two houses overlap, though they may touch edges. The task is to count the number of distinct positions where...

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Codeforces Beta Round 34 (Div. 2)

Codeforces Beta Round 34 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2000 | Time: 7m 19s Problem Name Rating Tags Solve Time Verified A Reconnaissance 2 800 implementation 1m 18s ✓ B Sale 900 greedy, sortings 1m 19s ✓ C Page Numbers 1300 expression-parsing, implementation, sortings 1m 7s ✓ D Road Map 1600 dfs-and-similar, graphs 1m 29s ✓ E Collisions 2000 brute-force, implementation,...

Practice › Codeforces Solutions › Codeforces Beta Round 42 (Div. 2) ›

CF 43E - Race

CF 43E - Race Rating: 2300 Tags: brute force, implementation, two pointers Solve time: 3m 27s Verified: yes Solution Problem Understanding We are asked to analyze a straight-line race of length s kilometers involving n cars. Each car has a list of driving segments, and each segment specifies a constant speed and a duration. The car moves at that speed for the given time before switching to the next segment....

Practice › Codeforces Solutions › Codeforces Beta Round 94 (Div. 2 Only) ›

CF 129A - Cookies

CF 129A - Cookies Rating: 900 Tags: implementation Solve time: 1m 44s Verified: yes Solution Problem Understanding We are given several bags of cookies, where each bag contains some number of cookies. Olga wants to steal exactly one bag. After removing that bag, the total number of cookies left behind must be even so the two sisters can split them equally. The task is to count how many bags Olga...

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CF 65A - Harry Potter and Three Spells

CF 65A - Harry Potter and Three Spells Rating: 1800 Tags: implementation, math Solve time: 2m 2s Verified: yes Solution Problem Understanding We have three transformation spells that convert one material into another. The first spell turns a grams of sand into b grams of lead. The second spell turns c grams of lead into d grams of gold. The third spell turns e grams of gold into f grams...

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Codeforces Beta Round 76 (Div. 1 Only)

Codeforces Beta Round 76 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1700-2600 | Time: 10m 8s Problem Name Rating Tags Solve Time Verified A Frames 1700 implementation 1m 51s ✓ B End of Exams 1900 greedy 1m 43s ✗ C Azembler 2500 brute-force, implementation 2m 1s ✓ D Flags 2500 dp, math, matrices 3m 28s ✗ E Lostborn 2600 dp, math, number-theory...

Practice › Codeforces Solutions › Codeforces Beta Round 53 ›

CF 57A - Square Earth?

CF 57A - Square Earth? Rating: 1300 Tags: dfs and similar, greedy, implementation Solve time: 1m 22s Verified: yes Solution Problem Understanding We are asked to find the shortest distance between two points lying on the perimeter of a square of side length n . The square is aligned with the axes, so its corners are at (0,0), (n,0), (0,n), and (n,n). The two points are guaranteed to lie on...

Practice › Codeforces Solutions › Codeforces Beta Round 9 (Div. 2 Only) ›

CF 9C - Hexadecimal's Numbers

CF 9C - Hexadecimal's Numbers Rating: 1200 Tags: brute force, implementation, math Solve time: 1m 10s Verified: yes Solution Problem Understanding We are asked to count how many numbers from 1 to n consist only of the digits 0 and 1 in their decimal representation. In other words, Hexadecimal's memory only stores numbers that, when written in base 10, contain no digits other than 0 or 1. For example, 1,...

Practice › Codeforces Solutions › Codeforces Beta Round 63 (Div. 2) ›

CF 69B - Bets

CF 69B - Bets Rating: 1200 Tags: greedy, implementation Solve time: 2m 1s Verified: yes Solution Problem Understanding Each athlete runs through a contiguous interval of sections. While an athlete is inside a section, they spend exactly t[i] time on that section, so the winner of a section is simply the active athlete with the smallest t . If several athletes have the same time, the smaller index wins. We...

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Codeforces Testing Round 1

Codeforces Testing Round 1 Type: Special | Problems: 3 | Verified: 3/3 | Rating range: 900-2200 | Time: 5m 34s Problem Name Rating Tags Solve Time Verified A 123-sequence 900 implementation 1m 38s ✓ B Right Triangles 1600 combinatorics 1m 38s ✓ C Circular RMQ 2200 data-structures 2m 18s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 73 (Div. 1 Only) ›

CF 87B - Vasya and Types

CF 87B - Vasya and Types Rating: 1800 Tags: implementation, strings Solve time: 1m 56s Verified: yes Solution Problem Understanding The language in this problem has only two real base types, void and errtype . Every other type is defined through typedef , and every query asks us to evaluate a type expression with typeof . A type expression is built from a base name plus some number of *...

Practice › Codeforces Solutions › Codeforces Beta Round 77 (Div. 2 Only) ›

CF 96A - Football

CF 96A - Football Rating: 900 Tags: implementation, strings Solve time: 1m 24s Verified: yes Solution Problem Understanding We are given a string made only of '0' and '1' . Each character represents the team of a football player standing in a line. A dangerous situation happens if at least seven consecutive players belong to the same team. The task is simply to check whether the string contains either seven...

Practice › Codeforces Solutions › Codeforces Beta Round 82 (Div. 2) ›

CF 106A - Card Game

CF 106A - Card Game Rating: 1000 Tags: implementation Solve time: 1m 37s Verified: yes Solution Problem Understanding We are given the trump suit for a game of Durak and two cards. The task is to decide whether the first card can beat the second card under the game rules. Each card has a rank and a suit. The ranks are ordered as: 6 < 7 < 8 < 9...

Practice › Codeforces Solutions › Codeforces Beta Round 25 (Div. 2 Only) ›

CF 25B - Phone numbers

CF 25B - Phone numbers Rating: 1100 Tags: implementation Solve time: 1m 24s Verified: yes Solution Problem Understanding We are given a string of digits representing a phone number. The task is to split this string into pieces where every piece has length either 2 or 3. The groups must appear in the original order, and they are joined with - characters in the output. The problem does not ask...

Practice › Codeforces Solutions › Codeforces Beta Round 62 ›

CF 68A - Irrational problem

CF 68A - Irrational problem Rating: 1100 Tags: implementation, number theory Solve time: 7m 4s Verified: yes Solution Problem Understanding We are asked to count integers $x$ in a given range $[a, b]$ that satisfy a certain remainder-based property. Petya has four distinct integers $p_1, p_2, p_3, p_4$. For any $x$, he can repeatedly take remainders of $x$ modulo these four numbers, but the order of operations is unknown. That...

Practice › Codeforces Solutions › Codeforces Beta Round 75 (Div. 2 Only) ›

CF 92A - Chips

CF 92A - Chips Rating: 800 Tags: implementation, math Solve time: 3m 15s Verified: yes Solution Problem Understanding We have n walruses arranged in a circle. The presenter starts with m chips and distributes them in order. Walrus 1 receives 1 chip, walrus 2 receives 2 chips, and so on up to walrus n , after which the cycle repeats again from walrus 1 . The process continues as long...

Practice › Codeforces Solutions › Codeforces Beta Round 49 (Div. 2) ›

CF 53A - Autocomplete

CF 53A - Autocomplete Rating: 1100 Tags: implementation Solve time: 3m 28s Verified: yes Solution Problem Understanding We are asked to implement a simplified autocomplete function. The input consists of a string s , which represents the text the user has typed so far, followed by a list of previously visited pages. The goal is to extend s into a complete page URL from the visited list, selecting the lexicographically...

Practice › Codeforces Solutions › Codeforces Beta Round 65 (Div. 2) ›

CF 71B - Progress Bar

CF 71B - Progress Bar Rating: 1300 Tags: implementation, math Solve time: 1m 7s Verified: yes Solution Problem Understanding We are asked to construct a graphical progress bar as an array of squares, where each square has a saturation value. The bar has a total of n squares, and the maximum saturation is k . The completion of the process is measured as t percent, and we need to reflect...

Practice › Codeforces Solutions ›

Codeforces Beta Round 50

Codeforces Beta Round 50 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1300-2700 | Time: 8m 47s Problem Name Rating Tags Solve Time Verified A Presents 1300 implementation 1m 19s ✓ B Cutting Jigsaw Puzzle 1800 hashing, implementation 1m 29s ✓ C First Digit Law 2000 dp, math, probabilities 1m 10s ✓ D Writing a Song 2100 brute-force, dp, strings 1m 3s ✓ E Vacuum \u0421leaner 2700...

Practice › Codeforces Solutions › Codeforces Beta Round 16 (Div. 2 Only) ›

CF 16A - Flag

CF 16A - Flag Rating: 800 Tags: implementation Solve time: 1m 8s Verified: yes Solution Problem Understanding We are given a rectangular grid representing a country’s flag. Each cell in the grid has a color, encoded as a digit from 0 to 9. The dimensions of the flag are $n$ rows by $m$ columns. The goal is to determine whether the flag is “striped” according to the new ISO standard....

Practice › Codeforces Solutions › Codeforces Beta Round 91 (Div. 2 Only) ›

CF 122B - Lucky Substring

CF 122B - Lucky Substring Rating: 1000 Tags: brute force, implementation Solve time: 1m 18s Verified: yes Solution Problem Understanding The problem asks us to find the "luckiest" substring of a given string of digits. By luckiest, we mean a substring that consists only of the digits 4 and 7, occurs in the string as many times as possible, and is the lexicographically smallest if there are ties. The input...

Practice › Codeforces Solutions › Codeforces Alpha Round 21 (Codeforces format) ›

CF 21A - Jabber ID

CF 21A - Jabber ID Rating: 1900 Tags: implementation, strings Solve time: 1m 37s Verified: no Solution Problem Understanding We need to validate whether a string follows the exact syntax of a Jabber ID. A valid ID has three possible pieces: username@hostname or username@hostname/resource The username and resource follow the same rules. They may contain only English letters, digits, and underscores. Their lengths must be between 1 and 16. The...

Practice › Codeforces Solutions › Codeforces Beta Round 39 ›

CF 40C - Berland Square

CF 40C - Berland Square Rating: 2300 Tags: implementation, math Solve time: 1m 38s Verified: yes Solution Problem Understanding We have two families of circles on the infinite plane. The first family contains circles centered at (x, 0) with radii 1, 2, ..., N . The second family contains circles centered at (y, 0) with radii 1, 2, ..., M . All circles are drawn simultaneously, and we need to...

Practice › Codeforces Solutions › Codeforces Beta Round 98 (Div. 2) ›

CF 137E - Last Chance

CF 137E - Last Chance Rating: 2000 Tags: data structures, implementation, strings Solve time: 1m 19s Verified: yes Solution Problem Understanding We are given a string s consisting of uppercase and lowercase Latin letters, and we are asked to analyze its substrings according to a specific property: a substring is "good" if the number of vowels it contains is at most twice the number of consonants. We want to find...

Practice › Codeforces Solutions › Codeforces Beta Round 72 (Div. 2 Only) ›

CF 84C - Biathlon

CF 84C - Biathlon Rating: 1700 Tags: binary search, implementation Solve time: 2m 57s Verified: no Solution Problem Understanding We are given a set of circular targets, all lying on the Ox axis, each defined by its center coordinate and radius. Valera shoots multiple times, and each shot has an (x, y) coordinate. The goal is to identify, for each target, the first shot that hits it, or -1 if...

Practice › Codeforces Solutions › Codeforces Beta Round 59 (Div. 2) ›

CF 63E - Sweets Game

CF 63E - Sweets Game Rating: 2000 Tags: bitmasks, dfs and similar, dp, games, implementation Solve time: 2m 13s Verified: yes Solution Problem Understanding The board is a fixed hexagon with 19 cells. Some cells contain chocolates, some are empty. Two players alternate moves, and a move consists of choosing a contiguous segment of chocolates that lies on a straight line parallel to one of the three hexagon directions. Every...

Practice › Codeforces Solutions › Codeforces Beta Round 42 (Div. 2) ›

CF 43B - Letter

CF 43B - Letter Rating: 1100 Tags: implementation, strings Solve time: 1m 31s Verified: yes Solution Problem Understanding We are given two strings. The first string is the newspaper headline, and the second string is the anonymous letter Vasya wants to build from it. Every non-space character from the headline can be used at most once. Spaces are special, they do not consume anything. If the letter text contains spaces,...

Practice › Codeforces Solutions ›

Unknown Language Round 4

Unknown Language Round 4 Type: Special | Problems: 10 | Verified: 10/10 | Rating range: 900-2300 | Time: 16m 22s Problem Name Rating Tags Solve Time Verified A Hexagonal numbers 900 *special, implementation 1m 24s ✓ B Gnikool Ssalg 1400 *special, implementation, strings 1m 24s ✓ C Decimal sum 1500 *special 1m 48s ✓ D Exponentiation 1500 *special 1m 51s ✓ E Tribonacci numbers 1600 *special 2m 6s ✓ F...

Practice › Codeforces Solutions ›

Codeforces Beta Round 62

Codeforces Beta Round 62 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1100-2900 | Time: 26m 18s Problem Name Rating Tags Solve Time Verified A Irrational problem 1100 implementation, number-theory 7m 4s ✓ B Energy exchange 1600 binary-search 7m 4s ✓ C Synchrophasotron 2200 brute-force 7m 3s ✓ D Half-decay tree 2500 data-structures, divide-and-conquer, dp 2m 50s ✓ E Contact 2900 geometry 2m 17s ✓

Practice › Codeforces Solutions › Yandex.Algorithm 2011: Finals ›

CF 97D - Robot in Basement

CF 97D - Robot in Basement Rating: 2700 Tags: bitmasks, brute force, implementation Solve time: 2m 39s Verified: yes Solution Problem Understanding We have a grid representing a basement. Some cells are walls, some are walkable, and exactly one walkable cell is the exit. A robot starts in an unknown walkable cell. We are given a fixed sequence of movement commands such as L , R , U , D...

Practice › Codeforces Solutions › Codeforces Beta Round 80 (Div. 2 Only) ›

CF 104A - Blackjack

CF 104A - Blackjack Rating: 800 Tags: implementation Solve time: 1m 14s Verified: yes Solution Problem Understanding We are given a simplified blackjack scenario where the first card is fixed: the queen of spades, which contributes 10 points. The player wants the sum of this card and a second card to equal a given number n , which ranges from 1 to 25. The task is to determine how many...

Practice › Codeforces Solutions ›

Codeforces Beta Round 80 (Div. 2 Only)

Codeforces Beta Round 80 (Div. 2 Only) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 800-800 | Time: 1m 14s Problem Name Rating Tags Solve Time Verified A Blackjack 800 implementation 1m 14s ✓

Practice › Codeforces Solutions ›

Codeforces Beta Round 35 (Div. 2)

Codeforces Beta Round 35 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1000-2100 | Time: 7m 52s Problem Name Rating Tags Solve Time Verified A Shell Game 1000 implementation 1m 26s ✓ B Warehouse 1700 implementation 1m 21s ✓ C Fire Again 1500 brute-force, dfs-and-similar, shortest-paths 2m 10s ✓ D Animals 1700 dp, greedy 1m 14s ✓ E Parade 2100 data-structures, sortings 1m 41s...

Practice › Codeforces Solutions › Codeforces Beta Round 5 ›

CF 5A - Chat Servers Outgoing Traffic

CF 5A - Chat Servers Outgoing Traffic Rating: 1000 Tags: implementation Solve time: 1m 9s Verified: yes Solution Problem Understanding We are given a sequence of chat server events. A user can join the chat, leave the chat, or send a message. Every time someone sends a message, the server delivers that message to every user currently inside the chat, including the sender. The cost of one message delivery is...

Practice › Codeforces Solutions › Codeforces Beta Round 63 (Div. 2) ›

CF 69E - Subsegments

CF 69E - Subsegments Rating: 1800 Tags: data structures, implementation Solve time: 1m 22s Verified: yes Solution Problem Understanding We are given an array of integers and a fixed window size k . For each contiguous subarray (segment) of length k , we need to find the largest element that appears exactly once within that segment. If no element appears exactly once, we output "Nothing". The input starts with the...

Practice › Codeforces Solutions ›

Codeforces Beta Round 79 (Div. 2 Only)

Codeforces Beta Round 79 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1200 | Time: 3m 36s Problem Name Rating Tags Solve Time Verified A Clothes 1200 brute-force 1m 42s ✓ B Sum of Digits 1000 implementation 1m 54s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 90 ›

CF 119B - Before Exam

CF 119B - Before Exam Rating: 1900 Tags: constructive algorithms, implementation, sortings Solve time: 2m 2s Verified: yes Solution Problem Understanding We have n theorems, and each theorem has a proficiency value assigned to it. The exam contains exactly k different cards. Every card contains exactly floor(n / k) distinct theorems, and no theorem appears in more than one card. Some theorems may remain unused if n is not divisible...

Practice › Codeforces Solutions › Codeforces Beta Round 65 (Div. 2) ›

CF 71D - Solitaire

CF 71D - Solitaire Rating: 2200 Tags: brute force, implementation Solve time: 2m 18s Verified: yes Solution Problem Understanding We are given a rectangular board filled with playing cards. The board size is at most $17 \times 17$, but the total number of placed cards never exceeds 52 because the deck has only 52 regular cards plus two jokers. A valid 3×3 square must satisfy one of two properties: All...

Practice › Codeforces Solutions › Yandex.Algorithm 2011: Round 1 ›

CF 85A - Domino

CF 85A - Domino Rating: 1300 Tags: constructive algorithms, implementation Solve time: 2m 9s Verified: yes Solution Problem Understanding We need to tile a 4 × n board using ordinary dominoes. Each domino covers exactly two neighboring cells, either horizontally or vertically. The tiling must satisfy an extra condition. Every vertical cut between column i and column i + 1 must slice through at least one horizontal domino. If a...

Practice › Codeforces Solutions › Codeforces Beta Round 1 ›

CF 1B - Spreadsheet

Problem Understanding The task gives spreadsheet cell coordinates written in one of two formats, and for every coordinate we must convert it into the other format. The first format is the usual Excel-style notation. A column is written using letters, then the row number follows immediately after it. For example, BC23 means column BC and row 23 . The tricky part is that the column behaves like a base-26 numbering...

Practice › Codeforces Solutions › School Team Contest 1 (Winter Computer School 2010/11) ›

CF 39F - Pacifist frogs

CF 39F - Pacifist frogs Rating: 1300 Tags: implementation Solve time: 1m 38s Verified: yes Solution Problem Understanding Thumbelina wants to cross a swamp by riding a single frog. The swamp contains hills numbered from 1 to n , where hill i is exactly i meters away from the island. A frog with jump length d lands on hills d, 2d, 3d, ... until its next jump would go beyond...

Practice › Codeforces Solutions › Codeforces Beta Round 60 ›

CF 65B - Harry Potter and the History of Magic

CF 65B - Harry Potter and the History of Magic Rating: 1700 Tags: brute force, greedy, implementation Solve time: 2m 33s Verified: no Solution Problem Understanding We are given a sequence of four-digit years. Each year may contain mistakes, but we are allowed to repair it by changing at most one digit. After all repairs, the sequence must become non-decreasing, and every resulting year must stay between 1000 and 2011...

Practice › Codeforces Solutions ›

Codeforces Beta Round 77 (Div. 2 Only)

Codeforces Beta Round 77 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 900-1300 | Time: 6m 15s Problem Name Rating Tags Solve Time Verified A Football 900 implementation, strings 1m 24s ✓ B Lucky Numbers (easy) 1300 binary-search, bitmasks, brute-force 4m 51s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 12 (Div 2 Only) ›

CF 12A - Super Agent

CF 12A - Super Agent Rating: 800 Tags: implementation Solve time: 1m 15s Verified: yes Solution Problem Understanding We are asked to check whether a password entered on a 3×3 keypad is symmetric with respect to its central button. The keypad is represented as a 3×3 grid of characters, where "X" indicates a pressed button and "." indicates an unpressed one. Central symmetry means that if you rotate the grid...

Practice › Codeforces Solutions ›

Codeforces Beta Round 70 (Div. 2)

Codeforces Beta Round 70 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 800-2300 | Time: 12m 16s Problem Name Rating Tags Solve Time Verified A Haiku 800 implementation, strings 3m 30s ✓ B Easter Eggs 1200 constructive-algorithms, implementation 1m 59s ✗ C Beaver Game 2000 dp, games, number-theory 2m 6s ✓ D Archer's Shot 2300 binary-search, geometry, math 2m 7s ✓ E Evacuation 2300...

Practice › Codeforces Solutions › Codeforces Beta Round 14 (Div. 2) ›

CF 14A - Letter

CF 14A - Letter Rating: 800 Tags: implementation Solve time: 1m 8s Verified: yes Solution Problem Understanding We are given a rectangular grid representing a sheet of graph paper with n rows and m columns. Some of the squares are shaded, marked by * , and the rest are unshaded, marked by . . Bob wants to cut out the smallest rectangle that contains all shaded squares so that he...

Practice › Codeforces Solutions › Unknown Language Round 4 ›

CF 130B - Gnikool Ssalg

CF 130B - Gnikool Ssalg Rating: 1400 Tags: *special, implementation, strings Solve time: 1m 24s Verified: yes Solution Problem Understanding The problem asks us to reverse a string. Given a sequence of characters, the output should be the same sequence but in the opposite order, so that the first character becomes the last, the second becomes the second-to-last, and so on. The input string is guaranteed to have between 1...

Practice › Codeforces Solutions › Codeforces Beta Round 7 ›

CF 7E - Defining Macros

CF 7E - Defining Macros Rating: 2600 Tags: dp, expression parsing, implementation Solve time: 1m 7s Verified: yes Solution Problem Understanding We are given a set of C-style #define macros and an expression, and we are asked to determine whether the expression becomes "suspicious" after macro substitution. In plain terms, a macro is a named expression, and whenever the name appears, it is replaced by its corresponding value. A suspicious...

Practice › Codeforces Solutions › Codeforces Beta Round 34 (Div. 2) ›

CF 34E - Collisions

CF 34E - Collisions Rating: 2000 Tags: brute force, implementation, math Solve time: 2m 6s Verified: yes Solution Problem Understanding We have several point-like balls moving on a one-dimensional line. Every ball starts at some coordinate with its own velocity and mass. Whenever two balls occupy the same position at the same time, they collide elastically, and their velocities change according to the standard physics formulas for one-dimensional elastic collisions....

Practice › Codeforces Solutions › Codeforces Beta Round 76 (Div. 2 Only) ›

CF 94B - Friends

CF 94B - Friends Rating: 1300 Tags: graphs, implementation, math Solve time: 1m 37s Verified: yes Solution Problem Understanding We have exactly five people. Some pairs of people know each other, and the input lists all such acquaintance relations. The task is to determine whether there exists either: Three people where every pair knows each other. Three people where no pair knows each other. This is naturally a graph problem....

Practice › Codeforces Solutions › Codeforces Beta Round 76 (Div. 2 Only) ›

CF 94A - Restoring Password

CF 94A - Restoring Password Rating: 900 Tags: implementation, strings Solve time: 1m 58s Verified: yes Solution Problem Understanding We are given an encrypted password represented as a binary string of length 80. The original password had exactly 8 decimal digits, and each digit was encoded into a block of 10 binary characters. The mapping between digits and binary blocks is also provided: after the encrypted string, we receive 10...

Practice › Codeforces Solutions › Manthan 2011 ›

CF 67A - Partial Teacher

CF 67A - Partial Teacher Rating: 1800 Tags: dp, graphs, greedy, implementation Solve time: 2m 6s Verified: yes Solution Problem Understanding We have a line of students, and for every adjacent pair we know only the relative order of their marks. If the relation character between positions i and i + 1 is: L , then student i must receive strictly more toffees than student i + 1 R ,...

Practice › Codeforces Solutions ›

Codeforces Beta Round 84 (Div. 2 Only)

Codeforces Beta Round 84 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1100 | Time: 5m 34s Problem Name Rating Tags Solve Time Verified A Nearly Lucky Number 800 implementation 2m 36s ✓ B Lucky String 1100 constructive-algorithms, strings 2m 58s ✓

Practice › Codeforces Solutions ›

Codeforces Beta Round 85 (Div. 2 Only)

Codeforces Beta Round 85 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1200 | Time: 3m 19s Problem Name Rating Tags Solve Time Verified A Petya and Strings 800 implementation, strings 1m 37s ✓ B Petya and Square 1200 implementation, math 1m 42s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 16 (Div. 2 Only) ›

CF 16B - Burglar and Matches

CF 16B - Burglar and Matches Rating: 900 Tags: greedy, implementation, sortings Solve time: 1m 13s Verified: yes Solution Problem Understanding We have a burglar who can carry exactly n matchboxes. In the warehouse, there are m containers. Each container i has a_i matchboxes, and every matchbox in that container contains b_i matches. The goal is to pick up to n matchboxes such that the total number of matches is...

Practice › Codeforces Solutions ›

Codeforces Beta Round 72 (Div. 2 Only)

Codeforces Beta Round 72 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 900-1700 | Time: 4m 27s Problem Name Rating Tags Solve Time Verified A Toy Army 900 math, number-theory 1m 30s ✓ C Biathlon 1700 binary-search, implementation 2m 57s ✗

Practice › Codeforces Solutions › Codeforces Beta Round 63 (Div. 2) ›

CF 69A - Young Physicist

CF 69A - Young Physicist Rating: 1000 Tags: implementation, math Solve time: 1m 43s Verified: yes Solution Problem Understanding We are given several force vectors acting on a body in three-dimensional space. Each vector has three components: its effect along the x-axis, y-axis, and z-axis. A body is in equilibrium only if the total force acting on it is zero in every direction. That means: the sum of all x-components...

Practice › Codeforces Solutions › Codeforces Beta Round 81 ›

CF 105C - Item World

CF 105C - Item World Rating: 2200 Tags: brute force, implementation, sortings Solve time: 3m 26s Verified: no Solution Problem Understanding We have a collection of items, and every item belongs to exactly one of three equipment classes: weapon, armor, or orb. Each item has three base stats, attack, defense, and resistance, plus a capacity telling us how many residents it can hold. Residents also come in three types. Gladiators...

Practice › Codeforces Solutions › Codeforces Alpha Round 21 (Codeforces format) ›

CF 21B - Intersection

CF 21B - Intersection Rating: 2000 Tags: implementation, math Solve time: 1m 21s Verified: yes Solution Problem Understanding Each input line describes a geometric object in the plane. The equation $$Ax + By + C = 0$$ represents a line. The task is to determine how many points belong to both lines at the same time. Two different non-parallel lines intersect at exactly one point. Two parallel but distinct lines...

Practice › Codeforces Solutions › School Team Contest 3 (Winter Computer School 2010/11) ›

CF 45A - Codecraft III

CF 45A - Codecraft III Rating: 900 Tags: implementation Solve time: 1m 14s Verified: yes Solution Problem Understanding We are given the current month as a string and an integer k representing how many months later a new game release will happen. The task is to determine the month after advancing exactly k months forward in the calendar. The calendar is cyclic. After December comes January again. Because of this,...

Practice › Codeforces Solutions ›

Codeforces Beta Round 53

Codeforces Beta Round 53 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1300-3000 | Time: 8m 25s Problem Name Rating Tags Solve Time Verified A Square Earth? 1300 dfs-and-similar, greedy, implementation 1m 22s ✓ B Martian Architecture 1600 implementation 1m 37s ✓ C Array 1900 combinatorics, math 1m 21s ✓ D Journey 2500 dp, math 2m 2s ✓ E Chess 3000 math, shortest-paths 2m 3s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 78 (Div. 1 Only) ›

CF 98A - Help Victoria the Wise

CF 98A - Help Victoria the Wise Rating: 1700 Tags: brute force, implementation Solve time: 2m 12s Verified: yes Solution Problem Understanding We have six gems, each with one of six possible colors. The six gems must be placed onto the six faces of a cube. Two placements are considered identical if one can be rotated into the other. The input is simply a string of length six. Each character...

Practice › Codeforces Solutions › Codeforces Beta Round 80 (Div. 1 Only) ›

CF 103A - Testing Pants for Sadness

CF 103A - Testing Pants for Sadness Rating: 1100 Tags: greedy, implementation, math Solve time: 1m 39s Verified: yes Solution Problem Understanding The test contains several questions that must be answered in order. Each question has multiple answer choices, and exactly one of them is correct. Vaganych does not know any correct answers in advance, but after making a mistake he remembers which options were wrong. Whenever he clicks a...

Practice › Codeforces Solutions ›

Codeforces Beta Round 87 (Div. 2 Only)

Codeforces Beta Round 87 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1100 | Time: 4m 3s Problem Name Rating Tags Solve Time Verified A Tram 800 implementation 1m 33s ✓ B Little Pigs and Wolves 1100 greedy, implementation 2m 30s ✓

Practice › Codeforces Solutions ›

Codeforces Beta Round 26 (Codeforces format)

Codeforces Beta Round 26 (Codeforces format) Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 900-2400 | Time: 7m 38s Problem Name Rating Tags Solve Time Verified A Almost Prime 900 number-theory 1m 18s ✓ B Regular Bracket Sequence 1400 greedy 1m 20s ✓ C Parquet 2000 combinatorics, constructive-algorithms, greedy 2m 9s ✗ D Tickets 2400 combinatorics, math, probabilities 1m 14s ✓ E Multithreading 2400 constructive-algorithms 1m 37s...

Practice › Codeforces Solutions ›

Codeforces Beta Round 2

Codeforces Beta Round 2 Type: Beta | Problems: 3 | Verified: 2/3 | Rating range: 1500-2600 | Time: 5m 52s Problem Name Rating Tags Solve Time Verified A Winner 1500 hashing, implementation 1m 9s ✓ B The least round way 2000 dp, math 3m 7s ✗ C Commentator problem 2600 geometry 1m 36s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 78 (Div. 1 Only) ›

CF 98B - Help King

CF 98B - Help King Rating: 2200 Tags: implementation, probabilities, trees Solve time: 1m 17s Verified: yes Solution Problem Understanding We are asked to simulate a fair random selection of one knight out of n using a coin that can only produce two outcomes. Each coin flip has an equal probability of landing heads or tails. The goal is to find the expected number of flips required to select a...

Practice › Codeforces Solutions › Unknown Language Round 1 ›

CF 64A - Factorial

CF 64A - Factorial Rating: 1300 Tags: *special, implementation Solve time: 1m 13s Verified: yes Solution Problem Understanding We are asked to compute the factorial of a given integer $n$. Factorial is the product of all positive integers up to $n$, so for $n = 3$, the factorial is $1 \times 2 \times 3 = 6$. The input is a single integer, and the output is the single integer result...

Practice › Codeforces Solutions ›

Codeforces Beta Round 44 (Div. 2)

Codeforces Beta Round 44 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 800-2200 | Time: 8m 58s Problem Name Rating Tags Solve Time Verified A Triangular numbers 800 brute-force, math 1m 10s ✓ B Coins 1200 implementation 1m 42s ✓ C Crossword 2000 implementation 2m 32s ✗ D Safe 2200 brute-force 1m 40s ✓ E Cannon 2200 data-structures, geometry, sortings 1m 54s ✗

Practice › Codeforces Solutions › Codeforces Beta Round 68 ›

CF 74A - Room Leader

CF 74A - Room Leader Rating: 1000 Tags: implementation Solve time: 1m 35s Verified: yes Solution Problem Understanding We are given the scoreboard data for every participant in a Codeforces room. Each contestant has a handle, a number of successful hacks, a number of unsuccessful hacks, and the points earned from problems A through E. The total score for one participant is computed as: the sum of the five problem...

Practice › Codeforces Solutions › Codeforces Beta Round 67 (Div. 2) ›

CF 75A - Life Without Zeros

CF 75A - Life Without Zeros Rating: 1000 Tags: implementation Solve time: 1m 34s Verified: yes Solution Problem Understanding We are given two positive integers, a and b . First we compute their normal sum c = a + b . Then we apply the same transformation to all three numbers: remove every digit 0 from their decimal representation. The question is whether the transformed equation still holds. In other...

Practice › Codeforces Solutions ›

Codeforces Beta Round 83 (Div. 2 Only)

Codeforces Beta Round 83 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1400 | Time: 9m 3s Problem Name Rating Tags Solve Time Verified A Palindromic Times 1000 implementation, strings 4m 56s ✓ B Datatypes 1400 math, sortings 4m 7s ✓

Practice › Codeforces Solutions ›

Codeforces Beta Round 78 (Div. 2 Only)

Codeforces Beta Round 78 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1300 | Time: 2m 45s Problem Name Rating Tags Solve Time Verified A Help Far Away Kingdom 800 strings 1m 25s ✓ B Help Chef Gerasim 1300 implementation, sortings 1m 20s ✓

Practice › Codeforces Solutions ›

Codeforces Beta Round 91 (Div. 2 Only)

Codeforces Beta Round 91 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1000 | Time: 2m 30s Problem Name Rating Tags Solve Time Verified A Lucky Division 1000 brute-force, number-theory 1m 12s ✓ B Lucky Substring 1000 brute-force, implementation 1m 18s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 5 ›

CF 5D - Follow Traffic Rules

CF 5D - Follow Traffic Rules Rating: 2100 Tags: implementation, math Solve time: 54s Verified: yes Solution Problem Understanding We are asked to compute the minimum travel time for a car moving along a straight road from Berland to Bercouver. The road has length l , and at a distance d from the start there is a speed sign that limits the car's instantaneous speed to w . The car...

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Codeforces Beta Round 77 (Div. 1 Only)

Codeforces Beta Round 77 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1600-2500 | Time: 7m 52s Problem Name Rating Tags Solve Time Verified A Hockey 1600 implementation, strings 1m 15s ✓ B Lucky Numbers 1800 dp, greedy 1m 52s ✓ C Volleyball 1900 shortest-paths 1m 21s ✓ D Horse Races 2500 dp, math 2m ✓ E Lucky Country 2500 dp, dsu, graphs...

Practice › Codeforces Solutions › Codeforces Beta Round 51 ›

CF 55A - Flea travel

CF 55A - Flea travel Rating: 1200 Tags: implementation, math Solve time: 1m 24s Verified: yes Solution Problem Understanding We have n positions arranged in a circle. The flea starts on one position. After the first minute it moves forward by 1 step, after the second minute by 2 steps, after the third minute by 3 steps, and so on. The question is whether this movement pattern eventually visits every...

Practice › Codeforces Solutions › Codeforces Beta Round 44 (Div. 2) ›

CF 47B - Coins

CF 47B - Coins Rating: 1200 Tags: implementation Solve time: 1m 42s Verified: yes Solution Problem Understanding We have three coins labeled A , B , and C . Every pair of coins has already been compared once using a balance scale, and each comparison tells us which coin is heavier. A line like A>B means coin A is heavier than coin B . Since heavier coins are assumed to...

Practice › Codeforces Solutions › Unknown Language Round 3 ›

CF 100B - Friendly Numbers

CF 100B - Friendly Numbers Rating: 1500 Tags: *special, implementation Solve time: 2m 19s Verified: yes Solution Problem Understanding We are asked to determine whether a set of non-zero integers forms a "friendly group," meaning every pair of numbers satisfies a divisibility relationship: one number divides the other. The input provides the number of integers, $n$, followed by a comma-separated list of the integers sorted in non-decreasing order. The output...

Practice › Codeforces Solutions › School Personal Contest #2 (Winter Computer School 2010/11) - Codeforces Beta Round 43 (ACM-ICPC Rules) ›

CF 46A - Ball Game

CF 46A - Ball Game Rating: 800 Tags: brute force, implementation Solve time: 1m 23s Verified: yes Solution Problem Understanding The children stand in a circle numbered from 1 to n . Child 1 starts with the ball. The first throw moves the ball forward by 1 position, the second throw moves it forward by 2 positions, the third throw by 3 positions, and so on. After exactly n -...

Practice › Codeforces Solutions ›

Codeforces Beta Round 7

Codeforces Beta Round 7 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1100-2600 | Time: 5m 10s Problem Name Rating Tags Solve Time Verified A Kalevitch and Chess 1100 brute-force, constructive-algorithms 1m 5s ✓ B Memory Manager 1600 implementation 1m 1s ✓ C Line 1800 math, number-theory 52s ✓ D Palindrome Degree 2200 hashing, strings 1m 5s ✓ E Defining Macros 2600 dp, expression-parsing, implementation 1m 7s...

Practice › Codeforces Solutions › Codeforces Beta Round 94 (Div. 1 Only) ›

CF 128D - Numbers

CF 128D - Numbers Rating: 2000 Tags: constructive algorithms, implementation Solve time: 1m 38s Verified: yes Solution Problem Understanding We are given a multiset of numbers and asked whether it is possible to arrange them in a circle so that every pair of adjacent numbers differs by exactly one. Conceptually, this means each number is a vertex on a cycle, and the absolute difference between neighbors must be 1. The...

Practice › Codeforces Solutions › Codeforces Alpha Round 20 (Codeforces format) ›

CF 20A - BerOS file system

CF 20A - BerOS file system Rating: 1700 Tags: implementation Solve time: 1m 20s Verified: yes Solution Problem Understanding We are given a filesystem path as a string. In this operating system, multiple consecutive '/' characters are treated exactly the same as a single '/' . That means paths like ///home//user///docs and /home/user/docs refer to the same location. The task is to convert the path into its normalized form. A...

Practice › Codeforces Solutions › School Personal Contest #2 (Winter Computer School 2010/11) - Codeforces Beta Round 43 (ACM-ICPC Rules) ›

CF 46D - Parking Lot

CF 46D - Parking Lot Rating: 1800 Tags: data structures, implementation Solve time: 1m 54s Verified: yes Solution Problem Understanding We have a parking segment represented by the interval [0, L] . Cars arrive one at a time, always driving from left to right, and each driver wants to park at the earliest possible position. If a car of length x parks with its back at coordinate p , then...

Practice › Codeforces Solutions ›

Codeforces Beta Round 28 (Codeforces format)

Codeforces Beta Round 28 (Codeforces format) Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1600-2800 | Time: 8m 33s Problem Name Rating Tags Solve Time Verified A Bender Problem 1600 implementation 1m 17s ✓ B pSort 1600 dfs-and-similar, dsu, graphs 1m 33s ✓ C Bath Queue 2200 combinatorics, dp, probabilities 1m 44s ✓ D Don't fear, DravDe is kind 2400 binary-search, data-structures, dp 1m 40s ✓ E...

Practice › Codeforces Solutions › Codeforces Beta Round 88 ›

CF 117E - Tree or not Tree

CF 117E - Tree or not Tree Rating: 2900 Tags: data structures, divide and conquer, graphs, implementation, trees Solve time: 3m 13s Verified: yes Solution Problem Understanding The graph has exactly n vertices and n edges. A connected graph with n vertices and n edges contains exactly one simple cycle. Every other edge belongs to a tree attached to that cycle. Initially every edge is turned off. A query picks...

Practice › Codeforces Solutions › School Regional Team Contest, Saratov, 2011 ›

CF 120A - Elevator

CF 120A - Elevator Rating: 1000 Tags: brute force, implementation, math Solve time: 1m 26s Verified: yes Solution Problem Understanding We are given two pieces of information about a person riding an elevator. The first input tells us which door the person used to enter, either the front door or the back door. The second input tells us which rail the person was holding, rail 1 or rail 2. The...

Practice › Codeforces Solutions › Codeforces Beta Round 73 (Div. 2 Only) ›

CF 88A - Chord

CF 88A - Chord Rating: 1200 Tags: brute force, implementation Solve time: 1m 17s Verified: yes Solution Problem Understanding We are given three musical notes, and the task is to classify the chord they form as either major, minor, or "strange". Notes are represented in the twelve-tone chromatic scale: C, C#, D, D#, E, F, F#, G, G#, A, B, H, and the scale is cyclic, so after H comes...

Practice › Codeforces Solutions ›

Codeforces Beta Round 40 (Div. 2)

Codeforces Beta Round 40 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 800-1900 | Time: 7m 28s Problem Name Rating Tags Solve Time Verified A Translation 800 implementation, strings 1m 14s ✓ B Martian Dollar 1400 brute-force 1m 8s ✓ C Email address 1300 expression-parsing, implementation 1m 41s ✗ D Pawn 1900 dp 1m 37s ✓ E 3-cycles 1900 constructive-algorithms, graphs, greedy 1m 48s...

Practice › Codeforces Solutions › Yandex.Algorithm 2011: Qualification 2 ›

CF 82A - Double Cola

CF 82A - Double Cola Rating: 1100 Tags: implementation, math Solve time: 1m 30s Verified: yes Solution Problem Understanding Five people stand in a queue in a fixed order: Sheldon, Leonard, Penny, Rajesh, Howard. Whenever the person at the front buys a cola, that person immediately creates a copy of themselves, and both copies go to the back of the queue. The queue keeps growing forever. We are given the...

Practice › Codeforces Solutions › Codeforces Beta Round 96 (Div. 1) ›

CF 132A - Turing Tape

CF 132A - Turing Tape Rating: 1300 Tags: implementation Solve time: 1m 39s Verified: yes Solution Problem Understanding We are given the final text printed by INTERCAL's strange "Turing Tape" output procedure. Each printed character was produced from one integer of an unknown array. The encoding process depends on the previous printed character, so every step is linked to the one before it. For a single character, the process works...

Practice › Codeforces Solutions › Codeforces Beta Round 58 ›

CF 62C - Inquisition

CF 62C - Inquisition Rating: 2300 Tags: geometry, implementation, sortings Solve time: 1m 32s Verified: yes Solution Problem Understanding We are given up to 100 triangles on the plane. Each triangle represents a black spot on a white square. Triangles may overlap, intersect, or even completely cover one another. The task is to compute the perimeter of the union of all black regions. The perimeter here is not the sum...

Practice › Codeforces Solutions › Codeforces Beta Round 37 ›

CF 37B - Computer Game

CF 37B - Computer Game Rating: 1800 Tags: greedy, implementation Solve time: 1m 56s Verified: yes Solution Problem Understanding The boss starts with max health and regenerates reg health every second. We own several scrolls. Each scroll can only be activated when the boss health is at most some percentage of the original health. Once activated, that scroll permanently adds its damage per second to our total damage output. The...

Practice › Codeforces Solutions › Codeforces Beta Round 95 (Div. 2) ›

CF 131A - cAPS lOCK

CF 131A - cAPS lOCK Rating: 1000 Tags: implementation, strings Solve time: 1m 16s Verified: yes Solution Problem Understanding The problem gives us a single word consisting of uppercase and lowercase Latin letters. This word may have been typed with the Caps Lock key unintentionally engaged. We are asked to correct such accidental capitalization. Specifically, we need to change the case of all letters in the word if either the...

Practice › Codeforces Solutions › Codeforces Beta Round 86 (Div. 1 Only) ›

CF 113A - Grammar Lessons

CF 113A - Grammar Lessons Rating: 1600 Tags: implementation, strings Solve time: 4m 41s Verified: yes Solution Problem Understanding We are given a single line containing several lowercase words separated by spaces. Every valid word in Petya's language belongs to exactly one grammatical category and exactly one gender, determined entirely by its suffix. There are only six legal suffixes: lios for masculine adjectives liala for feminine adjectives etr for masculine...

Practice › Codeforces Solutions › Codeforces Beta Round 85 (Div. 2 Only) ›

CF 112B - Petya and Square

CF 112B - Petya and Square Rating: 1200 Tags: implementation, math Solve time: 1m 42s Verified: yes Solution Problem Understanding We have a square board of size 2n × 2n , divided into unit cells. One cell is marked. We want to know whether it is possible to draw a cutting path along grid lines so that the board is split into two congruent parts after rotation, while the cutting...

Practice › Codeforces Solutions › Codeforces Beta Round 59 (Div. 2) ›

CF 63B - Settlers' Training

CF 63B - Settlers' Training Rating: 1200 Tags: implementation Solve time: 1m 35s Verified: yes Solution Problem Understanding We have a group of soldiers, each with a rank between 1 and k . During one training session, soldiers are grouped by equal rank. From every group whose rank is still below k , exactly one soldier is promoted by one level. The key detail is that promotions happen per distinct...

Practice › Codeforces Solutions › Unknown Language Round 3 ›

CF 100H - Battleship

CF 100H - Battleship Rating: 2100 Tags: *special, dfs and similar, implementation Solve time: 3m 4s Verified: yes Solution Problem Understanding We are given several 10 × 10 Battleship boards. Each cell is either empty or occupied by part of a ship. The task is to verify whether every occupied cell belongs to a valid fleet configuration. A valid Battleship fleet contains exactly one ship of length 4, two ships...

Practice › Codeforces Solutions ›

School Personal Contest #3 (Winter Computer School 2010/11) - Codeforces Beta Round 45 (ACM-ICPC Rules)

School Personal Contest #3 (Winter Computer School 2010/11) - Codeforces Beta Round 45 (ACM-ICPC Rules) Type: Beta | Problems: 8 | Verified: 6/8 | Rating range: 900-2800 | Time: 15m 12s Problem Name Rating Tags Solve Time Verified A Rock-paper-scissors 900 implementation, schedules 1m 31s ✓ B Land Lot 1200 brute-force, implementation 1m 47s ✓ C The Race 1800 math 1m 54s ✓ D Permutations 1500 greedy 2m 3s ✗...

Practice › Codeforces Solutions › Codeforces Beta Round 87 (Div. 2 Only) ›

CF 116A - Tram

CF 116A - Tram Rating: 800 Tags: implementation Solve time: 1m 33s Verified: yes Solution Problem Understanding We have a single tram traveling along a line with n stops, starting empty at the first stop and ending empty at the last stop. At each stop, a certain number of passengers exit before any new passengers enter. The input consists of pairs of integers for each stop: the number leaving and...

Practice › Codeforces Solutions › Codeforces Beta Round 77 (Div. 1 Only) ›

CF 95A - Hockey

CF 95A - Hockey Rating: 1600 Tags: implementation, strings Solve time: 1m 15s Verified: yes Solution Problem Understanding We are given a string representing a hockey team name and a list of forbidden substrings. Our task is to modify the original string so that any letter that is part of a forbidden substring can be replaced with another letter of our choosing. The replacements must maximize the occurrence of a...

Practice › Codeforces Solutions › Codeforces Beta Round 50 ›

CF 54A - Presents

CF 54A - Presents Rating: 1300 Tags: implementation Solve time: 1m 19s Verified: yes Solution Problem Understanding We are asked to estimate the minimum number of presents the Hedgehog will receive over the next N days. He has two rules governing present reception: every holiday he receives a gift, and he cannot go more than K days without receiving one. Today’s present is already accounted for, so we only consider...

Practice › Codeforces Solutions › Unknown Language Round 3 ›

CF 100C - A+B

CF 100C - A+B Rating: 1400 Tags: *special, implementation Solve time: 1m 27s Verified: yes Solution Problem Understanding The task looks trivial at first glance: read two integers and print their sum. The catch is hidden inside the constraints. Each number can contain up to 500 decimal digits, far larger than the range of standard 32-bit or 64-bit integers in many languages. We are given two positive integers, each written...

Practice › Codeforces Solutions › Codeforces Beta Round 61 (Div. 2) ›

CF 66C - Petya and File System

CF 66C - Petya and File System Rating: 1800 Tags: data structures, implementation Solve time: 2m 13s Verified: yes Solution Problem Understanding Each input line describes the full path of one file inside a file system. A path looks like: C:\folder1\folder2\file.txt The disk name is the root and is not considered a folder. Every component between the disk and the file is a folder. The last component is always a...

Practice › Codeforces Solutions › School Personal Contest #3 (Winter Computer School 2010/11) - Codeforces Beta Round 45 (ACM-ICPC Rules) ›

CF 48B - Land Lot

CF 48B - Land Lot Rating: 1200 Tags: brute force, implementation Solve time: 1m 47s Verified: yes Solution Problem Understanding The garden is represented as an n × m grid. Each cell contains either 0 or 1 . A 1 means there is a tree in that square, while 0 means the square is empty. We want to place a rectangular house plot somewhere inside the grid. The rectangle must...

Practice › Codeforces Solutions ›

Codeforces Beta Round 97 (Div. 2)

Codeforces Beta Round 97 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1100 | Time: 2m 54s Problem Name Rating Tags Solve Time Verified A Presents 800 implementation 1m 13s ✓ B Ternary Logic 1100 implementation, math 1m 41s ✓

Practice › Codeforces Solutions ›

School Personal Contest #2 (Winter Computer School 2010/11) - Codeforces Beta Round 43 (ACM-ICPC Rules)

School Personal Contest #2 (Winter Computer School 2010/11) - Codeforces Beta Round 43 (ACM-ICPC Rules) Type: Beta | Problems: 7 | Verified: 6/7 | Rating range: 800-2500 | Time: 10m 14s Problem Name Rating Tags Solve Time Verified A Ball Game 800 brute-force, implementation 1m 23s ✓ B T-shirts from Sponsor 1100 implementation 1m 13s ✓ C Hamsters and Tigers 1600 two-pointers 1m 18s ✓ D Parking Lot 1800 data-structures,...

Practice › Codeforces Solutions › Codeforces Beta Round 97 (Div. 2) ›

CF 136A - Presents

CF 136A - Presents Rating: 800 Tags: implementation Solve time: 1m 13s Verified: yes Solution Problem Understanding We are given a party scenario where Petya invited n friends, each of whom gave exactly one gift to another friend. The input lists, for each friend in order, the friend they gave a gift to. Our task is to invert this mapping: for each friend, we want to know who gave a...

Practice › Codeforces Solutions › Unknown Language Round 3 ›

CF 100F - Polynom

CF 100F - Polynom Rating: 1800 Tags: *special, implementation Solve time: 2m 26s Verified: yes Solution Problem Understanding We are given a polynomial already factorized into linear terms: $$p(x) = (x + a_1)(x + a_2)\dots(x + a_n)$$ The task is to expand this product and print the polynomial in the usual descending-power form: $$x^n + b_1x^{n-1} + \dots + b_n$$ The tricky part is not the expansion itself. The tricky...

Practice › Codeforces Solutions › Codeforces Beta Round 82 (Div. 2) ›

CF 106B - Choosing Laptop

CF 106B - Choosing Laptop Rating: 1000 Tags: brute force, implementation Solve time: 2m 3s Verified: yes Solution Problem Understanding Each laptop has four values: processor speed, RAM size, HDD size, and price. A laptop is considered outdated if there exists another laptop that is strictly better in all three technical characteristics at the same time. Price does not matter for deciding whether a laptop is outdated. After removing all...

Practice › Codeforces Solutions › Codeforces Beta Round 60 ›

CF 65E - Harry Potter and Moving Staircases

CF 65E - Harry Potter and Moving Staircases Rating: 2900 Tags: dfs and similar, implementation Solve time: 2m 47s Verified: no Solution Problem Understanding We are given an undirected multigraph. Floors are vertices, staircases are edges. Harry starts at floor 1 and wants to visit every floor at least once. The graph is dynamic. Between Harry's walks, Ron and Hermione may modify staircases. A modification picks one endpoint of an...

Practice › Codeforces Solutions › Codeforces Beta Round 31 (Div. 2, Codeforces format) ›

CF 31B - Sysadmin Bob

CF 31B - Sysadmin Bob Rating: 1500 Tags: greedy, implementation, strings Solve time: 1m 11s Verified: yes Solution Problem Understanding We are given a single string that represents multiple email addresses concatenated together with no separators. Each email address has the form A@B , where A and B are non-empty strings consisting of lowercase Latin letters. Our task is to split the string into a sequence of valid email addresses....

Practice › Codeforces Solutions ›

Codeforces Beta Round 76 (Div. 2 Only)

Codeforces Beta Round 76 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 900-1300 | Time: 3m 35s Problem Name Rating Tags Solve Time Verified A Restoring Password 900 implementation, strings 1m 58s ✓ B Friends 1300 graphs, implementation, math 1m 37s ✓

Practice › Codeforces Solutions ›

Codeforces Beta Round 67 (Div. 2)

Codeforces Beta Round 67 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1000-2400 | Time: 9m 31s Problem Name Rating Tags Solve Time Verified A Life Without Zeros 1000 implementation 1m 34s ✓ B Facetook Priority Wall 1500 expression-parsing, implementation, strings 2m 14s ✗ C Modified GCD 1600 binary-search, number-theory 1m 40s ✓ D Big Maximum Sum 2000 data-structures, dp, greedy 1m 34s ✓...

Practice › Codeforces Solutions ›

Codeforces Beta Round 58

Codeforces Beta Round 58 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1300-2700 | Time: 8m 15s Problem Name Rating Tags Solve Time Verified A A Student's Dream 1300 greedy, math 1m 13s ✓ B Tyndex.Brome 1800 binary-search, implementation 1m 18s ✓ C Inquisition 2300 geometry, implementation, sortings 1m 32s ✓ D Wormhouse 2300 dfs-and-similar, graphs 2m 15s ✗ E World Evil 2700 dp, flows 1m 57s...

Practice › Codeforces Solutions › Codeforces Beta Round 31 (Div. 2, Codeforces format) ›

CF 31C - Schedule

CF 31C - Schedule Rating: 1700 Tags: implementation Solve time: 58s Verified: yes Solution Problem Understanding We are given a list of n lessons, each with a start and end time, scheduled in a single room. Two lessons overlap if one starts before another ends. The goal is to find which single lesson can be removed so that the remaining lessons have no overlaps. If removing any single lesson produces...

Practice › Codeforces Solutions ›

Codeforces Beta Round 41

Codeforces Beta Round 41 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1400-2700 | Time: 10m 20s Problem Name Rating Tags Solve Time Verified A Guilty --- to the kitchen! 1400 greedy, implementation 1m 32s ✓ B Game of chess unfinished 1700 implementation 2m 3s ✓ C Safe cracking 2200 brute-force, constructive-algorithms 1m 2s ✓ D Strange town 2300 constructive-algorithms, math 1m 50s ✗ E Baldman and...

Practice › Codeforces Solutions › School Team Contest 2 (Winter Computer School 2010/11) ›

CF 44B - Cola

CF 44B - Cola Rating: 1500 Tags: implementation Solve time: 1m 9s Verified: yes Solution Problem Understanding We are asked to determine how many ways the organizers of a winter school can buy exactly n liters of cola using a limited supply of bottles in three sizes: 0.5-liter, 1-liter, and 2-liter. The inputs a , b , and c represent the number of bottles available in each size, respectively. The...

Practice › Codeforces Solutions › Codeforces Beta Round 52 (Div. 2) ›

CF 56A - Bar

CF 56A - Bar Rating: 1000 Tags: implementation Solve time: 1m 28s Verified: yes Solution Problem Understanding Vasya walks into a bar and sees several customers. For each customer, he only knows one piece of information: either the person’s age or the drink they ordered. He wants to determine how many people must still be checked to guarantee that nobody under 18 is drinking alcohol. A customer definitely needs checking...

#implementation

Codeforces Round 1091 (Div. 2) and CodeCraft 26

CF 2217D - Flip the Bit (Hard Version)

CF 2217B - Flip the Bit (Easy Version)

April Fools Day Contest

CF 171H - A polyline

CF 171F - ucyhf

Codeforces Round 1090 (Div. 4)

CF 2218F - The 67th Tree Problem

CF 2218A - The 67th Integer Problem

CF 168A - Wizards and Demonstration

Codeforces Round 114 (Div. 2)

Codeforces Beta Round 81

CF 2226G - Stop Spot

CF 2227D - Palindromex

CF 2227A - Koshary

CF 105D - Entertaining Geodetics

Codeforces Round 1096 (Div. 3)

CF 105A - Transmigration

Codeforces Round 282 (Div. 2)

Codeforces Round 279 (Div. 2)

CF 1973F - Maximum GCD Sum Queries

Codeforces Round 275 (Div. 2)

CF 1974B - Symmetric Encoding

CF 487A - Fight the Monster

Codeforces Round 942 (Div. 1)

CF 493A - Vasya and Football

CF 1976D - Invertible Bracket Sequences

Codeforces Round 941 (Div. 2)

CF 1954B - Make It Ugly

CF 1951E - No Palindromes

CF 1973C - Cat, Fox and Double Maximum

CF 1954E - Chain Reaction

CF 1976C - Job Interview

CF 1956E1 - Nene vs. Monsters (Easy Version)

CF 1945G - Cook and Porridge

Testing Round 11

CF 490E - Restoring Increasing Sequence

CF 1974D - Ingenuity-2

CF 1950E - Nearly Shortest Repeating Substring

CF 1950D - Product of Binary Decimals

CF 1957B - A BIT of a Construction

CF 495A - Digital Counter

CF 493B - Vasya and Wrestling

CF 1955C - Inhabitant of the Deep Sea

CF 483A - Counterexample

CF 1942D - Learning to Paint

Educational Codeforces Round 166 (Rated for Div. 2)

CF 485A - Factory

CF 1955B - Progressive Square

CF 1955G - GCD on a grid

Codeforces Round 940 (Div. 2) and CodeCraft-23

CF 493C - Vasya and Basketball

Codeforces Round 938 (Div. 3)

CF 1949J - Amanda the Amoeba

CF 1946C - Tree Cutting

CF 1956E2 - Nene vs. Monsters (Hard Version)

Codeforces Round 936 (Div. 2)

CF 1956D - Nene and the Mex Operator

CF 491A - Up the hill

CF 489C - Given Length and Sum of Digits...

CF 1976A - Verify Password

CF 490B - Queue

CF 1950C - Clock Conversion

Educational Codeforces Round 164 (Rated for Div. 2)

CF 1967F - Next and Prev

Codeforces Round 946 (Div. 3)

CF 1974F - Cutting Game

Codeforces Round 947 (Div. 1 + Div. 2)

CF 1950A - Stair, Peak, or Neither?

CF 1967A - Permutation Counting

CF 1950F - 0, 1, 2, Tree!

CF 1955E - Long Inversions

CF 1976B - Increase/Decrease/Copy

CF 1950B - Upscaling

Codeforces Round 276 (Div. 2)

CF 1975E - Chain Queries

CF 1967D - Long Way to be Non-decreasing

CF 1946D - Birthday Gift

CF 1975A - Bazoka and Mocha's Array