#competitive-programming

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...

CF 2217G - Down the Pivot

CF 2217G - Down the Pivot Rating: 2600 Tags: combinatorics, dp, math, trees Solve time: 1m 50s Verified: no Solution Problem Understanding We are working with rooted binary trees where each node carries a binary label, either zero or one. The tree structure is arbitrary as long as every node has at most two children. On top of that structure, we assign labels independently. The only allowed operation is very...

CF 2217E - Definitely Larger

CF 2217E - Definitely Larger Rating: 2000 Tags: binary search, constructive algorithms, data structures, graphs, greedy, sortings Solve time: 1m 39s Verified: no Solution Problem Understanding We are given a fixed permutation p of size n . Alongside it, we must construct another permutation q of the same size. The interaction between p and q defines a dominance relation: an index j is said to dominate an index i if...

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...

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...

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...

CF 171A - Mysterious numbers - 1

CF 171A - Mysterious numbers - 1 Rating: 1200 Tags: *special, constructive algorithms Solve time: 1m 43s Verified: yes Solution Problem Understanding This problem comes from an April Fools contest where the statement intentionally hides the real task. We are given two non-negative integers. The required operation is: Reverse the decimal representation of the second number. Add the result to the first number. Output the sum. For example, if the...

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...

CF 171G - Mysterious numbers - 2

CF 171G - Mysterious numbers - 2 Rating: 1600 Tags: *special Solve time: 2m Verified: yes Solution Problem Understanding We are given three small positive integers, a1, a2, and a3, each ranging from 1 to 20. The problem asks us to compute a single integer as output based on these three numbers. While the problem’s description is minimal, the underlying task is to enumerate all possible “mysterious numbers” that can...

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...

CF 171E - MYSTERIOUS LANGUAGE

CF 171E - MYSTERIOUS LANGUAGE Rating: 2000 Tags: *special Solve time: 1m 1s Verified: yes Solution Problem Understanding This is one of Codeforces' classic "special" problems. Unlike ordinary algorithmic tasks, there is no meaningful input to process and no data structure or optimization challenge to solve. The contest provides access to a language called Secret through the custom test environment. The actual challenge is to determine what programming language "Secret"...

CF 171D - Broken checker

CF 171D - Broken checker Rating: 1300 Tags: *special, brute force Solve time: 1m 14s Verified: yes Solution Problem Understanding This is one of the most unusual problems on Codeforces. The input is supposed to contain a single integer between 1 and 5. There are only five official test cases. The output must be a single integer between 1 and 3. The crucial detail is that there is no actual...

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...

CF 2218D - The 67th OEIS Problem

CF 2218D - The 67th OEIS Problem Rating: 1100 Tags: constructive algorithms, greedy, math, number theory Solve time: 2m 4s Verified: no Solution Problem Understanding We are asked to construct sequences of integers of length $n$ such that the greatest common divisor (gcd) of consecutive elements is always distinct. Each test case provides a number $n$, and for each, we must output one valid sequence of length $n$. The output...

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...

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...

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...

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 ✓

Codeforces Round 1093 (Div. 1)

Codeforces Round 1093 (Div. 1) Type: Div. 1 | Problems: 1 | Verified: 0/1 | Rating range: - | Time: 3m 30s Problem Name Rating Tags Solve Time Verified A Grid L - brute-force, constructive-algorithms, math 3m 30s ✗

CF 2219A - Grid L

CF 2219A - Grid L Rating: - Tags: brute force, constructive algorithms, math, number theory Solve time: 3m 30s Verified: no Solution Problem Understanding An $n \times m$ grid consists of all unit segments that form the lattice. Every cell contributes edges, but neighboring cells share edges, so the total number of unit segments in the whole grid is not $4nm$. We are given two types of pieces. A straight...

CF 2222D - Permutation Construction

CF 2222D - Permutation Construction Rating: - Tags: constructive algorithms, data structures, sortings Solve time: 4m 9s Verified: no Solution Problem Understanding We are given an array $a$ of length $n$. We must construct a permutation $p$ of indices $1$ to $n$. For any pair of positions $i<j$, the pair contributes to the score only if it is an inversion in $p$, meaning $p_i>p_j$. Each such inversion contributes the interval...

Codeforces Round 1095 (Div. 2)

Codeforces Round 1095 (Div. 2) Type: Div. 2 | Problems: 7 | Verified: 0/7 | Rating range: - | Time: 23m 23s Problem Name Rating Tags Solve Time Verified A Disturbing Distribution - greedy, math 3m 10s ✗ B Everything Everywhere - greedy, math, number-theory 3m 22s ✗ C Mental Monumental (Easy Version) - binary-search, data-structures, greedy 6m 17s ✗ D Reserved Reversals - constructive-algorithms, dp, greedy 2m 22s ✗...

CF 2226D - Reserved Reversals

CF 2226D - Reserved Reversals Rating: - Tags: constructive algorithms, dp, greedy, math Solve time: 2m 22s Verified: no Solution Problem Understanding We are given several test cases, each consisting of an array. The task is to decide whether we can transform each array into a non-decreasing order using a specific operation: we may pick any subarray, compute its minimum and maximum values, and reverse it, but only if the...

CF 105E - Lift and Throw

CF 105E - Lift and Throw Rating: 2500 Tags: brute force Solve time: 2m 33s Verified: yes Solution Problem Understanding We are given three characters, each standing on a different position along a one-dimensional half-line. Each position is an integer starting at 1, and each character has a movement range and a throwing range. Movement range defines how far they can move to an unoccupied position, and throwing range defines...

CF 2225F - String Cutting

CF 2225F - String Cutting Rating: - Tags: binary search, brute force, greedy, hashing, string suffix structures, strings Solve time: 2m 54s Verified: no Solution Problem Understanding A string $s$ must be split into several contiguous pieces. Each piece has length at least $l$, and the total number of pieces is at least $k$. After cutting, all pieces are sorted lexicographically, and the piece in position $k$ of this sorted...

CF 2227C - Snowfall

CF 2227C - Snowfall Rating: - Tags: constructive algorithms, math Solve time: 4m 24s Verified: no Solution Problem Understanding A subarray product is divisible by $6$ if and only if the product contains at least one factor $2$ and at least one factor $3$. For each number, only its divisibility by $2$ and $3$ matters. The exact value is irrelevant. Every element belongs to one of four groups: $A$: divisible...

Educational Codeforces Round 189 (Rated for Div. 2)

Educational Codeforces Round 189 (Rated for Div. 2) Type: Div. 2 | Problems: 5 | Verified: 0/5 | Rating range: - | Time: 14m 18s Problem Name Rating Tags Solve Time Verified B Alternating String - brute-force, greedy 3m 12s ✗ C Red-Black Pairs - dp, greedy 2m 34s ✗ D Exceptional Segments - bitmasks, brute-force, math 3m 1s ✗ E Covering Points with Circles - constructive-algorithms, geometry, math 2m...

CF 2222E - Seek the Truth

CF 2222E - Seek the Truth Rating: - Tags: binary search, bitmasks, constructive algorithms, interactive Solve time: 1m 59s Verified: no Solution Problem Understanding The original problem is interactive, but the version used for judging after the contest is the hacked format. Instead of interacting with a judge, each test case directly gives us the hidden values n , k , and c . The interactive story is useful because...

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...

CF 2226C - Mental Monumental (Easy Version)

CF 2226C - Mental Monumental (Easy Version) Rating: - Tags: binary search, data structures, greedy, math, two pointers Solve time: 6m 17s Verified: no Solution Problem Understanding Each array element can be modified independently. For a value $x$, we may choose any positive integer $b$, then replace $x$ by $x \bmod b$. The goal is to maximize the MEX of the resulting array. Since the operation is applied independently to...

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...

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...

CF 2225D - Exceptional Segments

CF 2225D - Exceptional Segments Rating: - Tags: bitmasks, brute force, math Solve time: 3m 1s Verified: no Solution Problem Understanding The sequence $[1,2,\dots,n]$ is fixed. For any interval $[l,r]$, the value of interest is the bitwise XOR of all integers in that interval. A segment is valid when two conditions hold simultaneously. The index $x$ lies inside the segment, so $l \le x \le r$. The XOR of the...

CF 2222G - Statistics on Tree

CF 2222G - Statistics on Tree Rating: - Tags: binary search, brute force, dfs and similar, divide and conquer, graphs, trees Solve time: 6m 33s Verified: no Solution Problem Understanding We are given a tree. For a pair of vertices $(u,v)$, we remove every edge belonging to the unique simple path between them. After those edges are deleted, the tree breaks into several connected components. The value of the pair...

CF 2227F - It Just Keeps Going Sideways

CF 2227F - It Just Keeps Going Sideways Rating: - Tags: binary search, data structures, dp, greedy, math Solve time: 5m 5s Verified: no Solution Problem Understanding Each column contains cubes stacked from height $1$ up to height $a_i$. After gravity turns to the right, cubes never change height. Cubes at the same height slide independently and occupy the rightmost available positions on that horizontal level. It is useful to...

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...

CF 2222B - Artistic Balance Tree

CF 2222B - Artistic Balance Tree Rating: - Tags: greedy, sortings Solve time: 3m 53s Verified: no Solution Problem Understanding We have an array, and before each marking operation we are allowed to reverse any odd-length segment centered at some position. After that reversal, the element currently sitting at index x_i becomes marked. The subtle detail is that marks belong to elements, not positions. If an element gets marked and...

CF 2227H - Fallen Leaves

CF 2227H - Fallen Leaves Rating: - Tags: dfs and similar, dp, trees Solve time: 2m 56s Verified: no Solution Problem Understanding We are given a tree and a fixed set of vertices consisting of all leaves in the original tree. These leaves are determined once from the initial structure and do not change during the process. We then repeatedly pick two distinct unused leaves, add the length of the...

CF 2227B - Party Monster

CF 2227B - Party Monster Rating: - Tags: greedy Solve time: 3m 38s Verified: no Solution Problem Understanding We are given a string made only of opening and closing parentheses. In one move, we are allowed to take a contiguous block, remove it, and then reinsert its characters anywhere in the remaining string, with full freedom to permute those removed characters and place each one independently. The question is whether,...

CF 2226F - Inversion Invasion

CF 2226F - Inversion Invasion Rating: - Tags: math, number theory Solve time: 1m 41s Verified: no Solution Problem Understanding For every divisor $d\mid n$, define $$G_d={v\in[1,n]\mid \gcd(v,n)=d}.$$ The array $a$ gradually fixes some positions. If $a_i=d\neq 0$, then position $i$ must contain a value from $G_d$. Unfixed positions may contain any remaining values. A valid permutation exists only if, for every divisor $d$, $$c_d \le |G_d|,$$ where $c_d$ is...

CF 2225B - Alternating String

CF 2225B - Alternating String Rating: - Tags: brute force, greedy Solve time: 3m 12s Verified: no Solution Problem Understanding We are given a binary string made of only a and b . The goal is to check whether we can turn it into a perfectly alternating string, meaning every adjacent pair of characters differs. We are allowed to perform at most one operation. In that operation we pick a...

CF 2225C - Red-Black Pairs

CF 2225C - Red-Black Pairs Rating: - Tags: dp, greedy Solve time: 2m 34s Verified: no Solution Problem Understanding We are given a grid with $2$ rows and $n$ columns. Each cell is initially colored either red or black. We are allowed to repaint any cells, and the goal is to reach a final coloring with the following property: the entire $2n$ cells can be partitioned into exactly $n$ disjoint...

CF 105B - Dark Assembly

CF 105B - Dark Assembly Rating: 1800 Tags: brute force, probabilities Solve time: 2m 19s Verified: yes Solution Problem Understanding We have a small assembly of n senators, each defined by a level and a loyalty score. Loyalty is a probability that a senator votes in favor of a proposal, given in 10% increments. If more than half of senators vote yes, the proposal passes. If the vote fails, the...

CF 2222C - Median Partition

CF 2222C - Median Partition Rating: - Tags: dp, math Solve time: 2m 36s Verified: no Solution Setup The simulator maintains a global simulated time variable $CLOCK$ and executes each MIX instruction by dispatching to a routine that models its effect on registers, memory, and timing. The I/O instructions considered here are restricted to devices $16$ and $18$. Device $16$ represents the read-card unit, and device $18$ represents the printer...

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...

Spectral::Cup 2026 Round 1 (Codeforces Round 1094, Div. 1 + Div. 2)

Spectral::Cup 2026 Round 1 (Codeforces Round 1094, Div. 1 + Div. 2) Type: Div. 1+2 | Problems: 6 | Verified: 0/6 | Rating range: - | Time: 23m 39s Problem Name Rating Tags Solve Time Verified A A Wonderful Contest - brute-force, dp, math 4m 29s ✗ B Artistic Balance Tree - greedy, sortings 3m 53s ✗ C Median Partition - dp, math 2m 36s ✗ D Permutation Construction -...

CF 2225E - Covering Points with Circles

CF 2225E - Covering Points with Circles Rating: - Tags: constructive algorithms, geometry, math Solve time: 2m 37s Verified: no Solution Problem Understanding We are given up to $10^4$ integer points on the plane and a fixed radius $r$. We must output the centers of several circles, all having radius $r$, such that the centers have integer coordinates and no two circles overlap in positive area. Touching is allowed, but...

CF 2227E - It All Went Sideways

CF 2227E - It All Went Sideways Rating: - Tags: binary search, data structures, dp, greedy Solve time: 2m 57s Verified: no Solution Problem Understanding Each test case gives a sequence of column heights. Think of column i as a vertical stack of unit blocks, occupying rows 1 up to a_i . All blocks in a row are aligned across columns. Then gravity is suddenly redefined: instead of falling down,...

CF 2226B - Everything Everywhere

CF 2226B - Everything Everywhere Rating: - Tags: greedy, math, number theory Solve time: 3m 22s Verified: no Solution Problem Understanding We are given a permutation of the integers from 1 to n . For every contiguous subarray, we look at three quantities: its maximum value, its minimum value, the GCD of all values inside it. A subarray is called good when $$\max - \min = \gcd(\text{all elements})$$ The task...

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...

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,...

CF 2226A - Disturbing Distribution

CF 2226A - Disturbing Distribution Rating: - Tags: greedy, math Solve time: 3m 10s Verified: no Solution Problem Understanding We are given a sequence of positive integers. We repeatedly remove groups of elements until nothing remains. Each group must respect two constraints: if we look at the chosen indices in increasing order, the corresponding values must be nondecreasing, and the indices themselves must be strictly increasing as usual for a...

CF 2227G - Drowning

CF 2227G - Drowning Rating: - Tags: binary search, data structures, math Solve time: 2m 57s Verified: no Solution Problem Understanding Ta có một mảng số nguyên dương. Một phép giảm chọn ba phần tử liên tiếp sao cho phần tử giữa nhỏ hơn tổng hai phần tử hai bên. Khi đó bộ ba $$(c_{i-1},c_i,c_{i+1})$$ được thay bằng một giá trị duy nhất $$x=c_{i-1}-c_i+c_{i+1}.$$ Mỗi lần thực hiện, độ dài...

CF 2226E - Mental Monumental (Hard Version)

CF 2226E - Mental Monumental (Hard Version) Rating: - Tags: data structures, greedy, math, two pointers Solve time: 3m 59s Verified: no Solution Problem Understanding We are given an array, and we look at it prefix by prefix. For each prefix we are allowed to transform each element independently exactly once using a very permissive operation: pick any integer $b_i \ge 1$, replace $a_i$ with the remainder of dividing it...

CF 2222A - A Wonderful Contest

CF 2222A - A Wonderful Contest Rating: - Tags: brute force, dp, math Solve time: 4m 29s Verified: no Solution Problem Understanding Each problem in the contest is worth at most 100 points. If a problem has $a_i$ subtasks, then every solved subtask contributes $$\frac{100}{a_i}$$ points, and $a_i$ is guaranteed to divide 100. This means every problem contributes one of the values $$0,\ \frac{100}{a_i},\ 2\cdot\frac{100}{a_i},\ \ldots,\ 100.$$ For a contestant,...

CF 1945F - Kirill and Mushrooms

CF 1945F - Kirill and Mushrooms Rating: 1900 Tags: data structures, sortings Solve time: 1m 9s Verified: no Solution Problem Understanding Kirill wants to gather mushrooms under a Wise Oak to brew an elixir. Each mushroom has a magic power, and the strength of an elixir made from a group of mushrooms is the product of the count of mushrooms and the minimum magic power among them. Kirill can pick...

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...

CF 1975B - 378QAQ and Mocha's Array

CF 1975B - 378QAQ and Mocha's Array Rating: 1000 Tags: brute force, greedy, math, sortings Solve time: 5m 18s Verified: no Solution

CF 492E - Vanya and Field

CF 492E - Vanya and Field Rating: 2000 Tags: math Solve time: 5m 20s Verified: no Solution

CF 493D - Vasya and Chess

CF 493D - Vasya and Chess Rating: 1700 Tags: constructive algorithms, games, math Solve time: 1m 25s Verified: yes Solution Problem Understanding We have an $n \times n$ board. The white queen starts at the top-left corner $(1,1)$, and the black queen starts at the top-right corner $(1,n)$. Every other square contains a green pawn. A move is mandatory. On each turn, a player must capture some piece with their...

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...

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

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

CF 1974B - Symmetric Encoding

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

CF 1975C - Chamo and Mocha's Array

CF 1975C - Chamo and Mocha's Array Rating: 1200 Tags: binary search, brute force, greedy Solve time: 5m 19s Verified: no Solution

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...

CF 1974C - Beautiful Triple Pairs

CF 1974C - Beautiful Triple Pairs Rating: 1400 Tags: combinatorics, data structures Solve time: 5m 16s Verified: no Solution

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

Codeforces Round 276 (Div. 1)

Codeforces Round 276 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 0/4 | Rating range: 1700-2500 | Time: 26m 55s Problem Name Rating Tags Solve Time Verified A Bits 1700 bitmasks, constructive-algorithms 5m 23s ✗ B Maximum Value 2100 binary-search, math, sortings 10m 57s ✗ D Kindergarten 2400 data-structures, dp, greedy 5m 17s ✗ E Sign on Fence 2500 binary-search, constructive-algorithms, data-structures 5m 18s ✗

Codeforces Round 278 (Div. 2)

Codeforces Round 278 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 0/2 | Rating range: 1100-1900 | Time: 21m 45s Problem Name Rating Tags Solve Time Verified A Giga Tower 1100 brute-force 10m 47s ✗ B Candy Boxes 1900 brute-force, constructive-algorithms, math 10m 58s ✗

CF 483B - Friends and Presents

CF 483B - Friends and Presents Rating: 1800 Tags: binary search, math Solve time: 5m 22s Verified: no Solution

CF 1943A - MEX Game 1

CF 1943A - MEX Game 1 Rating: 1300 Tags: games, greedy Solve time: 1m 9s Verified: yes Solution Problem Understanding We are asked to analyze a two-player game on an array of non-negative integers. Alice begins with an empty array c , and on her turn, she takes any element from the initial array a and appends it to c . Bob, on his turn, removes any element from a...

CF 1968A - Maximize?

CF 1968A - Maximize? Rating: 800 Tags: brute force, math, number theory Solve time: 1m 6s Verified: no Solution Problem Understanding We are given a small positive integer $x$. For each such value, we need to choose another integer $y$ strictly smaller than $x$, and we want to maximize the expression $\gcd(x, y) + y$. The interaction between the two terms is important. The gcd term grows when $y$ shares...

CF 480E - Parking Lot

CF 480E - Parking Lot Rating: 2800 Tags: data structures, divide and conquer Solve time: 5m 24s Verified: no Solution

CF 1949K - Make Triangle

CF 1949K - Make Triangle Rating: 2800 Tags: constructive algorithms, math Solve time: 2m 29s Verified: yes Solution Problem Understanding We are given a multiset of positive integers and three required group sizes. Every number must belong to exactly one of the three groups, and each group must contain exactly the requested number of elements. After splitting the numbers, we look only at the three group sums. If those sums...

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

CF 1944B - Equal XOR

CF 1944B - Equal XOR Rating: 1100 Tags: bitmasks, constructive algorithms Solve time: 1m 19s Verified: no Solution Problem Understanding We are given an array of length $2n$ where every number from $1$ to $n$ appears exactly twice. You can think of it as $n$ paired cards scattered in a line. The first $n$ positions form a left block and the last $n$ positions form a right block. The task...

Codeforces Round 282 (Div. 1)

Codeforces Round 282 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 1/4 | Rating range: 2000-3200 | Time: 24m 13s Problem Name Rating Tags Solve Time Verified B Obsessive String 2000 dp, strings 10m 58s ✗ C Helping People 2600 dp, probabilities 42s ✓ D Birthday 2700 data-structures, dfs-and-similar, dp 1m 4s ✗ E Sharti 3200 data-structures, games 11m 29s ✗

CF 1955A - Yogurt Sale

CF 1955A - Yogurt Sale Rating: 800 Tags: math Solve time: 54s Verified: yes Solution Problem Understanding Maxim wants to buy exactly n yogurts from a store where a single yogurt costs a burles, but there is a promotion offering two yogurts for b burles. For each test case, we must calculate the minimum amount he can spend to buy exactly n yogurts. The input specifies multiple test cases, each...

CF 1965B - Missing Subsequence Sum

CF 1965B - Missing Subsequence Sum Rating: 1800 Tags: bitmasks, constructive algorithms, greedy, number theory Solve time: 1m 17s Verified: no Solution Problem Understanding We are asked to construct an array of non-negative integers such that the sums of all subsequences cover every integer from 1 to $n$, except for a single forbidden sum $k$. Each test case gives the upper bound $n$ and the forbidden sum $k$. The output...

CF 484B - Maximum Value

CF 484B - Maximum Value Rating: 2100 Tags: binary search, math, sortings, two pointers Solve time: 10m 57s Verified: no Solution Problem Understanding We are given a list of integers, and we are allowed to pick two positions in it, say one value acts as a dividend and the other as a divisor. The only restriction is that the dividend must be at least as large as the divisor. For...

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...

CF 484D - Kindergarten

CF 484D - Kindergarten Rating: 2400 Tags: data structures, dp, greedy Solve time: 5m 17s Verified: no Solution

CF 491B - New York Hotel

CF 491B - New York Hotel Rating: 2100 Tags: greedy, math Solve time: 11m 40s Verified: no Solution Problem Understanding The city is a rectangular grid. Every hotel and every restaurant is located at an intersection with coordinates $(x,y)$. Moving between neighboring intersections costs one kilometer, so the travel distance between two points is the Manhattan distance $$|x_1-x_2| + |y_1-y_2|.$$ All friends start from their hotels and travel to the...

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....

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 ✗

CF 1974D - Ingenuity-2

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

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 ,...

CF 1951I - Growing Trees

CF 1951I - Growing Trees Rating: 3200 Tags: binary search, constructive algorithms, flows, graphs, greedy Solve time: 1m 37s Verified: no Solution Problem Understanding We are given a connected simple undirected graph with up to 50 vertices and at most 50 edges. Each edge can be used multiple times in a constructed multigraph, and we control how many copies of each edge we create through a non-negative integer array $x$....

CF 1967B2 - Reverse Card (Hard Version)

CF 1967B2 - Reverse Card (Hard Version) Rating: 2200 Tags: brute force, math, number theory Solve time: 1m 30s Verified: no Solution Problem Understanding We are asked to count ordered pairs of integers $(a, b)$ with $1 \le a \le n$ and $1 \le b \le m$ such that $b \cdot \gcd(a, b)$ is divisible by $a+b$. The inputs are multiple test cases, each specifying a pair of limits $n$...

CF 1974A - Phone Desktop

CF 1974A - Phone Desktop Rating: 800 Tags: greedy, math Solve time: 5m 17s Verified: no Solution

CF 1954C - Long Multiplication

CF 1954C - Long Multiplication Rating: 1200 Tags: greedy, math, number theory Solve time: 1m 13s Verified: no Solution Problem Understanding We are given two very large integers represented as strings, both having the same number of digits. Every digit is between 1 and 9, so there are no zeros to complicate positional effects or leading zero issues. The only operation allowed is to swap digits at the same position...

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...

CF 1943E2 - MEX Game 2 (Hard Version)

CF 1943E2 - MEX Game 2 (Hard Version) Rating: 3300 Tags: binary search, greedy, two pointers Solve time: 1m 18s Verified: no Solution Problem Understanding We are given a multiset of integers, but instead of listing it explicitly, we receive frequencies of each value from 0 up to some maximum m. Alice and Bob remove elements from this multiset until nothing remains. Alice builds a new sequence c by picking...

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...

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...

CF 1967C - Fenwick Tree

CF 1967C - Fenwick Tree Rating: 2300 Tags: bitmasks, brute force, combinatorics, data structures, dp, math, trees Solve time: 1m 2s Verified: no Solution Problem Understanding We are asked to reverse a Fenwick Tree construction. A Fenwick Tree is normally defined for an array a of length n such that each element s_k stores the sum of a contiguous subarray of a whose length is the lowest set bit of...

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 ✗

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....

CF 1951H - Thanos Snap

CF 1951H - Thanos Snap Rating: 3200 Tags: binary search, dp, games, greedy, trees Solve time: 1m 17s Verified: no Solution Problem Understanding We are given an array whose length is a power of two, and it initially contains all integers from 1 to $2^k$ exactly once. So the array is just a permutation, but its initial order matters. A game is played on this array. A parameter $t$ is...

CF 1952F - Grid

CF 1952F - Grid Rating: - Tags: *special, brute force Solve time: 1m 12s Verified: no Solution Problem Understanding We are given a fixed-size grid of 21 rows and 21 columns. Each cell contains either 0 or 1 . The grid should be viewed as a map where each cell is a square tile, and tiles with the same value may form connected regions through shared edges. The task is...

CF 1943D2 - Counting Is Fun (Hard Version)

CF 1943D2 - Counting Is Fun (Hard Version) Rating: 2800 Tags: combinatorics, dp Solve time: 1m 9s Verified: no Solution Problem Understanding We are asked to count certain arrays with bounded elements that satisfy a combinatorial property. Specifically, consider all arrays of length n where each element is between 0 and k . An array is called good if, starting from it, we can repeatedly choose any contiguous subarray of...

CF 485B - Valuable Resources

CF 485B - Valuable Resources Rating: 1300 Tags: brute force, greedy Solve time: 11m 9s Verified: no Solution Problem Understanding We are asked to build a square city on a 2D Cartesian map such that it encloses all given mines, represented as points with integer coordinates. The sides of the square must remain parallel to the axes, and our goal is to minimize the area of the square. The input...

Codeforces Round 942 (Div. 2)

Codeforces Round 942 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 0/1 | Rating range: 900-900 | Time: 5m 40s Problem Name Rating Tags Solve Time Verified B Coin Games 900 games 5m 40s ✗

CF 485A - Factory

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

European Championship 2024 - Online Mirror (Unrated, ICPC Rules, Teams Preferred)

European Championship 2024 - Online Mirror (Unrated, ICPC Rules, Teams Preferred) Type: ICPC/IOI | Problems: 11 | Verified: 5/11 | Rating range: 1500-3300 | Time: 28m 1s Problem Name Rating Tags Solve Time Verified A Grove 3300 brute-force, dfs-and-similar, dp 2m 41s ✓ B Charming Meals 1500 binary-search, brute-force, greedy 1m 44s ✓ C Annual Ants' Gathering 1900 dfs-and-similar, dp, greedy 4m 48s ✓ D Funny or Scary? 2600 constructive-algorithms...

CF 1949B - Charming Meals

CF 1949B - Charming Meals Rating: 1500 Tags: binary search, brute force, greedy, sortings Solve time: 1m 44s Verified: yes Solution Problem Understanding We have two arrays of size n . The array a contains the spiciness values of the appetizers, and the array b contains the spiciness values of the main dishes. Every appetizer must be paired with exactly one main dish, and every main dish must be used...

CF 1958D - Staircase

CF 1958D - Staircase Rating: 1600 Tags: *special Solve time: 1m 14s Verified: no Solution Problem Understanding We are given a line of staircase steps, each step either needing repair or already fine. If a step is fine, it behaves like a zero in the input. If it is broken, it carries a positive cost value that represents its repair difficulty. The repair process is constrained by days. Each day...

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...

Codeforces Round 934 (Div. 2)

Codeforces Round 934 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 800-1100 | Time: 2m 14s Problem Name Rating Tags Solve Time Verified A Destroying Bridges 800 graphs, greedy, math 55s ✓ B Equal XOR 1100 bitmasks, constructive-algorithms 1m 19s ✗

CF 1949F - Dating

CF 1949F - Dating Rating: 2200 Tags: greedy, sortings, trees Solve time: 1m 57s Verified: no Solution Problem Understanding Each user can be viewed as a set of activities. We need to find two users whose sets satisfy three conditions simultaneously: They share at least one activity. The first user has at least one activity that the second user does not have. The second user has at least one activity...

CF 1968B - Prefiquence

CF 1968B - Prefiquence Rating: 800 Tags: greedy, two pointers Solve time: 1m 7s Verified: yes Solution Problem Understanding We are asked to find, for each test case, the longest prefix of a binary string a that can appear as a subsequence in another binary string b . A prefix is simply the first k characters of a , and a subsequence of b is formed by deleting zero or...

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

CF 1973D - Cat, Fox and Maximum Array Split

CF 1973D - Cat, Fox and Maximum Array Split Rating: 2400 Tags: brute force, interactive, math Solve time: 5m 14s Verified: no Solution

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

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...

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 ✗

CF 1976E - Splittable Permutations

CF 1976E - Splittable Permutations Rating: 2500 Tags: combinatorics, data structures, dfs and similar, greedy, math, trees Solve time: 5m 16s Verified: no Solution

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...

CF 1967E1 - Again Counting Arrays (Easy Version)

CF 1967E1 - Again Counting Arrays (Easy Version) Rating: 3100 Tags: combinatorics, dp, fft, math Solve time: 1m 13s Verified: no Solution Problem Understanding We are given a fixed starting height $b_0$ and we imagine building an integer path $b_0, b_1, \ldots, b_n$ where each step moves by exactly $+1$ or $-1$, but the path is never allowed to go below zero. This is a standard “walk on the non-negative...

CF 1949G - Scooter

CF 1949G - Scooter Rating: 2300 Tags: graphs, greedy Solve time: 3m 15s Verified: no Solution Problem Understanding Each building has two independent pieces of information. The first string describes what class is held there. A building may need a mathematics professor, a computer science professor, or no professor at all. The second string describes which professor is initially located there. A building may contain a mathematics professor, a computer...

CF 1951C - Ticket Hoarding

CF 1951C - Ticket Hoarding Rating: 1400 Tags: greedy, math, sortings Solve time: 59s Verified: no Solution Problem Understanding The task is to buy exactly k concert tickets over n days, with each day offering a ticket price a_i . You are limited to buying at most m tickets per day. Additionally, every ticket you buy increases the price of all future tickets by the number of tickets bought on...

CF 1955D - Inaccurate Subsequence Search

CF 1955D - Inaccurate Subsequence Search Rating: 1400 Tags: data structures, two pointers Solve time: 46s Verified: yes Solution Problem Understanding We are asked to count subsegments of length m in an array a that are “good” relative to another array b of length m . A subsegment is considered good if, after rearranging its elements, at least k of them match elements from b . In practice, this means...

CF 494B - Obsessive String

CF 494B - Obsessive String Rating: 2000 Tags: dp, strings Solve time: 10m 58s Verified: no Solution Problem Understanding We are given two strings, s and t . Our goal is to count the number of ways to select one or more non-overlapping substrings from s such that each selected substring contains t somewhere inside it. A substring is defined by its starting and ending indices, and “non-overlapping” means that...

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...

CF 1958A - 1-3-5

CF 1958A - 1-3-5 Rating: 1100 Tags: *special, dp Solve time: 47s Verified: yes Solution Problem Understanding We are asked to construct an exact sum using coins of values 1, 3, and 5. For each target amount n, we want to pay exactly n using any number of 3 and 5 coins, and we are only forced to use 1-coins when it becomes unavoidable. The task is to minimize how...

CF 1945D - Seraphim the Owl

CF 1945D - Seraphim the Owl Rating: 1300 Tags: dp, greedy Solve time: 1m 20s Verified: yes Solution Problem Understanding We are given a queue of n people waiting to ask Seraphim the Owl a question. Kirill arrives at the end of the line and wants to move forward so that he is among the first m people. To move forward, he can swap with someone ahead in the queue,...

CF 1954D - Colored Balls

CF 1954D - Colored Balls Rating: 1800 Tags: combinatorics, dp, math, sortings Solve time: 1m 43s Verified: no Solution Problem Understanding We are given a collection of balls, each assigned one of n distinct colors, where color i has a_i balls. We are allowed to group these balls, but each group can have at most two balls, and no two balls in the same group can have the same color....

CF 482A - Diverse Permutation

CF 482A - Diverse Permutation Rating: 1200 Tags: constructive algorithms, greedy Solve time: 11m 3s Verified: no Solution Problem Understanding We are asked to construct a permutation of integers from 1 to n such that the set of absolute differences between consecutive elements contains exactly k distinct values. Concretely, if the permutation is [p1, p2, ..., pn] , then the list [|p1 - p2|, |p2 - p3|, ..., |pn-1 -...

CF 486E - LIS of Sequence

CF 486E - LIS of Sequence Rating: 2200 Tags: data structures, dp, greedy, hashing, math Solve time: 5m 17s Verified: no Solution

CF 1952G - Mathematician Takeover

CF 1952G - Mathematician Takeover Rating: - Tags: *special, binary search, dfs and similar, math Solve time: 1m 8s Verified: no Solution Problem Understanding We are given a single real number $x$ between 1 and 100, expressed to exactly three decimal places. The task is to compute a real number result from $x$, with the requirement that the answer's absolute or relative error does not exceed $10^{-4}$. The problem does...

CF 482D - Random Function and Tree

CF 482D - Random Function and Tree Rating: 2700 Tags: combinatorics, dp, trees Solve time: 5m 18s Verified: no Solution

CF 1951A - Dual Trigger

CF 1951A - Dual Trigger Rating: 900 Tags: constructive algorithms, greedy, math Solve time: 51s Verified: yes Solution Problem Understanding We are given a row of lamps, all initially off. We can perform one type of operation any number of times: choose two lamps that are currently off and are not next to each other, and turn them both on simultaneously. Our task is to determine, for multiple test cases,...

CF 1942A - Farmer John's Challenge

CF 1942A - Farmer John's Challenge Rating: 800 Tags: constructive algorithms, math Solve time: 1m 37s Verified: no Solution Problem Understanding We need to construct an array of length n such that exactly k of its cyclic shifts are sorted in nondecreasing order. A cyclic shift chooses some position as the new beginning of the array and wraps the remaining elements around. For example, the shifts of [1, 2, 3]...

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...

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...

CF 1942B - Bessie and MEX

CF 1942B - Bessie and MEX Rating: 1100 Tags: constructive algorithms, math Solve time: 1m 18s Verified: no Solution Problem Understanding We are given an array a of length n , constructed from some unknown permutation p of the integers 0 through n-1 . Each element of a satisfies the relation a[i] = MEX(p[1..i]) - p[i] . The task is to reconstruct any valid permutation p that produces this a...

CF 1951B - Battle Cows

CF 1951B - Battle Cows Rating: 1200 Tags: binary search, data structures, greedy Solve time: 1m 24s Verified: no Solution Problem Understanding We have a line of cows, each with a unique Cowdeforces rating, and they compete in a sequential tournament. The tournament begins with the first two cows, and each subsequent match is between the winner of the previous match and the next cow in line. A cow with...

CF 1958G - Observation Towers

CF 1958G - Observation Towers Rating: 2400 Tags: *special Solve time: 1m 18s Verified: yes Solution Problem Understanding Each observation tower sits at a fixed position on a number line from 1 to n and has a current viewing radius given by its height. A tower can “see” every integer point whose distance from its position does not exceed its height. Increasing the height expands this symmetric visibility interval, and...

CF 1942G - Bessie and Cards

CF 1942G - Bessie and Cards Rating: 2800 Tags: combinatorics, dp, math Solve time: 3m 51s Verified: yes Solution Problem Understanding The deck contains four kinds of cards. A draw-0 card consumes one playable card from your hand and gives nothing back. A draw-1 card replaces itself. A draw-2 card consumes one card and gives two new cards, so it increases your future drawing power by one. There are also...

CF 1951G - Clacking Balls

CF 1951G - Clacking Balls Rating: 3100 Tags: combinatorics, math, probabilities Solve time: 1m 25s Verified: no Solution Problem Understanding We are given a circle of baskets numbered from 1 to $m$, and $n$ balls initially placed in distinct baskets. Alice repeatedly chooses one of the balls uniformly at random and moves it clockwise to the next basket. If that basket already contains a ball, the existing ball is thrown...

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...

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...

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...

CF 1942H - Farmer John's Favorite Intern

CF 1942H - Farmer John's Favorite Intern Rating: 3500 Tags: data structures, dp, flows, trees Solve time: 1m 20s Verified: no Solution Problem Understanding We are asked to maintain a rooted tree where each node starts with zero peaches. Two kinds of operations can happen. In a growth operation at node $x$, we can increase the number of peaches on the parent of $x$ or any node in the subtree...

CF 1949A - Grove

CF 1949A - Grove Rating: 3300 Tags: brute force, dfs and similar, dp, geometry, probabilities Solve time: 2m 41s Verified: yes Solution Problem Understanding Every tree is planted at an integer lattice point. Around that point we place a disk of radius r , representing the root system. Two conditions must hold. The entire disk must stay inside the square lawn. Since the lawn is the square [0,n] × [0,n]...

CF 491A - Up the hill

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

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...

CF 489E - Hiking

CF 489E - Hiking Rating: 2300 Tags: binary search, dp Solve time: 5m 18s Verified: no Solution

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...

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 ✗

CF 494C - Helping People

CF 494C - Helping People Rating: 2600 Tags: dp, probabilities Solve time: 42s Verified: yes Solution Problem Understanding We are tasked with calculating the expected maximum wealth of a group of people after a series of charitable recommendations. Each person starts with a known amount of money. There are several recommendations, each specifying a segment of people to receive one dollar, and each recommendation has a probability that it will...

CF 1943E1 - MEX Game 2 (Easy Version)

CF 1943E1 - MEX Game 2 (Easy Version) Rating: 2900 Tags: binary search, brute force, greedy Solve time: 1m 13s Verified: no Solution Problem Understanding We are asked to simulate a two-player game on an array of integers, but with a compressed representation where we only know the frequencies of each integer. Alice and Bob take turns, with Alice always picking a single element to add to her personal array,...

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...

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...

CF 1976A - Verify Password

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

CF 1948D - Tandem Repeats?

CF 1948D - Tandem Repeats? Rating: 1700 Tags: brute force, strings, two pointers Solve time: 2m 48s Verified: no Solution Problem Understanding We are given a string consisting of lowercase letters and wildcard characters. Each wildcard can later be replaced by any lowercase letter we choose. After fixing all wildcards, we look at every substring of the resulting string and ask whether it can be split into two consecutive halves...

CF 1949E - Damage per Second

CF 1949E - Damage per Second Rating: 2900 Tags: brute force, math Solve time: 1m 7s Verified: no Solution Problem Understanding We are asked to distribute a fixed number of skill points between two attributes: damage per hit and hits per second, in order to minimize the total time to kill a sequence of monsters. Each monster has a health value $h_i$, and the time to kill it is determined...

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...

CF 1945E - Binary Search

CF 1945E - Binary Search Rating: 1700 Tags: binary search, constructive algorithms, greedy Solve time: 1m 21s Verified: no Solution Problem Understanding We are given a permutation of size $n$, meaning every number from $1$ to $n$ appears exactly once, but in some arbitrary order. Along with it, we are given a target value $x$ that definitely exists somewhere in the array. We are allowed to perform at most two...

CF 1956B - Nene and the Card Game

CF 1956B - Nene and the Card Game Rating: 800 Tags: games, greedy Solve time: 53s Verified: yes Solution Problem Understanding We are given a multiset of $2n$ cards, where every number from $1$ to $n$ appears exactly twice in total. These cards are split evenly between two players, you and Nene, so each of you holds $n$ cards. We are only given your hand; Nene’s hand is implicitly determined...

CF 1957A - Stickogon

CF 1957A - Stickogon Rating: 800 Tags: constructive algorithms, greedy Solve time: 43s Verified: yes Solution Problem Understanding We are given a collection of sticks, each with an integer length. The goal is to build as many regular polygons as possible using these sticks, with the restriction that each side of a polygon must be exactly one stick, and no stick can be reused. A regular polygon requires at least...

CF 1948F - Rare Coins

CF 1948F - Rare Coins Rating: 2500 Tags: combinatorics, math, probabilities Solve time: 2m 56s Verified: no Solution Problem Understanding Each bag contains a fixed number of gold coins and a number of silver coins. Gold coins always contribute one unit of value. Silver coins are uncertain, each silver coin independently contributes either 0 or 1 with equal probability. The randomness is only in silver coins; everything else is deterministic....

CF 1958E - Yet Another Permutation Constructive

CF 1958E - Yet Another Permutation Constructive Rating: 1900 Tags: *special, constructive algorithms Solve time: 1m 4s Verified: no Solution Problem Understanding We are given a permutation, which is just an ordering of the numbers from 1 to n. We repeatedly apply a transformation that removes elements which are strictly smaller than at least one of their immediate neighbors. After each round, the remaining elements form a shorter sequence, and...

CF 482C - Game with Strings

CF 482C - Game with Strings Rating: 2600 Tags: bitmasks, dp, probabilities Solve time: 1m 44s Verified: no Solution Problem Understanding We are given a collection of distinct strings of the same length. One string is secretly chosen uniformly at random. Our goal is to determine the expected number of questions needed to identify the chosen string. Each question asks for the character at a position that has not been...

CF 1958J - Necromancer

CF 1958J - Necromancer Rating: 3200 Tags: *special Solve time: 1m 12s Verified: yes Solution Problem Understanding We are simulating a very specific combat process on a fixed line of monsters, and answering many independent queries on subsegments of that line. Each query picks a segment $[l, r]$ and then runs a deterministic procedure that always attacks the leftmost remaining monster, repeatedly until it dies, and then permanently converts it...

CF 1965A - Everything Nim

CF 1965A - Everything Nim Rating: 1400 Tags: games, greedy, math, sortings Solve time: 1m 24s Verified: no Solution Problem Understanding We are given several independent games, each defined by a list of piles containing stones. Two players alternate turns. A move consists of choosing an integer $k$ that does not exceed the smallest nonempty pile, then simultaneously subtracting $k$ stones from every pile that is still nonempty. Any pile...

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,...

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...

Kotlin Heroes: Episode 10

Kotlin Heroes: Episode 10 Type: Kotlin | Problems: 10 | Verified: 7/10 | Rating range: 1100-3200 | Time: 11m 13s Problem Name Rating Tags Solve Time Verified A 1-3-5 1100 *special, dp 47s ✓ B Clock in the Pool 1400 *special, math 44s ✓ C Firewood 1500 *special 1m ✓ D Staircase 1600 *special 1m 14s ✗ E Yet Another Permutation Constructive 1900 *special, constructive-algorithms 1m 4s ✗ F Narrow...

CF 1974E - Money Buys Happiness

CF 1974E - Money Buys Happiness Rating: 1800 Tags: dp Solve time: 5m 17s Verified: no Solution

CF 1949H - Division Avoidance

CF 1949H - Division Avoidance Rating: 3100 Tags: greedy, math Solve time: 5m 53s Verified: no Solution Problem Understanding The process starts with a single cell at (0, 0) . Whenever we divide a cell (x, y) , that cell disappears and produces (x + 1, y) and (x, y + 1) . A division is only legal if neither child is currently present. We are given a finite set...

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...

Codeforces Global Round 25

Codeforces Global Round 25 Type: Global | Problems: 9 | Verified: 1/9 | Rating range: 900-3200 | Time: 11m 49s Problem Name Rating Tags Solve Time Verified A Dual Trigger 900 constructive-algorithms, greedy, math 51s ✓ B Battle Cows 1200 binary-search, data-structures, greedy 1m 24s ✗ C Ticket Hoarding 1400 greedy, math, sortings 59s ✗ D Buying Jewels 2000 constructive-algorithms, greedy, math 1m 19s ✗ E No Palindromes 2000 brute-force,...

CF 1943F - Minimum Hamming Distance

CF 1943F - Minimum Hamming Distance Rating: 3500 Tags: dp Solve time: 1m 21s Verified: no Solution Problem Understanding We are given two binary strings of equal length. The first string, call it the reference string, defines a constraint on how a valid target string must behave. The second string is the one we want to stay as close as possible to after we adjust it into a valid configuration....

Educational Codeforces Round 163 (Rated for Div. 2)

Educational Codeforces Round 163 (Rated for Div. 2) Type: Div. 2 | Problems: 6 | Verified: 2/6 | Rating range: 800-3100 | Time: 11m 57s Problem Name Rating Tags Solve Time Verified A Special Characters 800 brute-force, constructive-algorithms 1m 17s ✗ C Arrow Path 1300 brute-force, constructive-algorithms, dfs-and-similar 56s ✓ D Tandem Repeats? 1700 brute-force, strings, two-pointers 2m 48s ✗ E Clique Partition 2100 brute-force, constructive-algorithms, graphs 2m 41s ✗...

CF 1965F - Conference

CF 1965F - Conference Rating: 3300 Tags: data structures, flows Solve time: 1m 8s Verified: no Solution Problem Understanding We are given a collection of time intervals, each interval belonging to a different lecturer. Lecturer i is available on a continuous range of days from li to ri, and can be assigned to at most one conference day. Our task is not to pick lecturers directly, but to choose a...

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...

CF 484A - Bits

CF 484A - Bits Rating: 1700 Tags: bitmasks, constructive algorithms Solve time: 5m 23s Verified: no Solution

CF 1973B - Cat, Fox and the Lonely Array

CF 1973B - Cat, Fox and the Lonely Array Rating: 1300 Tags: binary search, bitmasks, data structures, greedy, math, two pointers Solve time: 5m 16s Verified: no Solution

CF 1974G - Money Buys Less Happiness Now

CF 1974G - Money Buys Less Happiness Now Rating: 2000 Tags: data structures, greedy, sortings Solve time: 5m 13s Verified: no Solution

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

CF 1951F - Inversion Composition

CF 1951F - Inversion Composition Rating: 2500 Tags: constructive algorithms, data structures, greedy Solve time: 1m 56s Verified: no Solution Problem Understanding We are asked to construct a permutation q of size n such that the sum of inversions of q and the composition q ∘ p equals a given target k . The input permutation p is fixed, and inversions count how many pairs of indices are out of...

CF 1952I - Dark Matter

CF 1952I - Dark Matter Rating: - Tags: *special, bitmasks, geometry Solve time: 48s Verified: yes Solution Problem Understanding The input describes a single arithmetic-style expression consisting of integers combined with the + operator. The key difference from standard arithmetic is that + does not mean numeric addition. Instead, each operation combines two numbers by treating them as binary strings and stitching them together. Concretely, when we see an expression...

CF 490F - Treeland Tour

CF 490F - Treeland Tour Rating: 2200 Tags: data structures, dfs and similar, dp, trees Solve time: 10m 49s Verified: no Solution Problem Understanding We are given a tree with n cities, each with a known population. The tree is described by n-1 bidirectional roads connecting the cities. The "Road Accident" band wants to plan a tour along a path in this tree, visiting cities in sequence without repeating, and...

CF 1942C2 - Bessie's Birthday Cake (Hard Version)

CF 1942C2 - Bessie's Birthday Cake (Hard Version) Rating: 1700 Tags: geometry, greedy, math Solve time: 2m 8s Verified: no Solution Problem Understanding We have a regular polygon with n vertices arranged on a circle. Some x vertices are already available for use. We may additionally choose at most y more vertices. After selecting vertices, we are allowed to draw non-intersecting diagonals whose endpoints belong to the selected set. Every...

CF 487C - Prefix Product Sequence

CF 487C - Prefix Product Sequence Rating: 2300 Tags: constructive algorithms, math, number theory Solve time: 5m 22s Verified: no Solution

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...

CF 1945B - Fireworks

CF 1945B - Fireworks Rating: 900 Tags: math, number theory Solve time: 1m 25s Verified: yes Solution Problem Understanding Two firework machines start at time zero and then keep launching fireworks periodically. The first machine fires at times that are multiples of a , and the second fires at multiples of b . Every firework, once launched, stays visible for m + 1 minutes, so a firework launched at time...

CF 1975H - 378QAQ and Core

CF 1975H - 378QAQ and Core Rating: 3500 Tags: greedy, strings Solve time: 5m 19s Verified: no Solution

CF 1965E - Connected Cubes

CF 1965E - Connected Cubes Rating: 3100 Tags: constructive algorithms, games Solve time: 1m 10s Verified: no Solution Problem Understanding We are given an $n \times m$ grid sitting at height $z=1$, where each cell already contains a unit cube with a color. You are allowed to stack additional colored cubes at integer coordinates above this base layer, but you are blocked from using any cell on the coordinate planes...

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...

CF 489F - Special Matrices

CF 489F - Special Matrices Rating: 2100 Tags: combinatorics, dp Solve time: 10m 48s Verified: no Solution Problem Understanding We are asked to count the number of special square matrices of size n × n , where each row and column contains exactly two ones, and all other cells are zeros. We are given the first m rows explicitly, and the task is to count all matrices that extend these...

CF 491C - Deciphering

CF 491C - Deciphering Rating: 2300 Tags: flows, graph matchings Solve time: 41s Verified: yes Solution Problem Understanding We are asked to decipher a message that has been encoded by a simple substitution cipher. Each letter in the original message is replaced with a fixed letter, so the mapping is one-to-one: different letters map to different letters, and the same letter always maps to the same letter. Maria Ivanovna has...

CF 487E - Tourists

CF 487E - Tourists Rating: 3200 Tags: data structures, dfs and similar, graphs, trees Solve time: 10m 55s Verified: no Solution Problem Understanding We are given a network of cities connected by roads, where each city sells a souvenir at a certain price. Queries can either change the souvenir price in a city or ask for the minimum possible price a tourist can pay when traveling from one city to...

CF 1952C - They Have Fooled

CF 1952C - They Have Fooled Rating: - Tags: *special, brute force, schedules Solve time: 52s Verified: yes Solution Problem Understanding The input to this problem is a single integer $n$, with $0 \le n \le 12$. Despite how small this looks, the task is not about iterating or simulating anything directly from this number in a naive arithmetic sense. Instead, the problem asks for a fixed value that depends...

CF 1958C - Firewood

CF 1958C - Firewood Rating: 1500 Tags: *special Solve time: 1m Verified: yes Solution Problem Understanding Monocarp has a single log of wood that weighs exactly $2^n$ grams. He needs to split this log into pieces such that he can assemble exactly $k$ grams of wood for today's fireplace, leaving the remaining $2^n-k$ grams for tomorrow. Each minute, Monocarp can split a log of weight $x > 1$ into two...

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...

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...

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...

CF 1956C - Nene's Magical Matrix

CF 1956C - Nene's Magical Matrix Rating: 1600 Tags: constructive algorithms, greedy, math Solve time: 57s Verified: yes Solution Problem Understanding We are given a square matrix of size $n \times n$ initially filled with zeroes. Nene can perform two types of operations: either set an entire row to a permutation of $1$ through $n$ or set an entire column to such a permutation. The goal is to maximize the...

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....

CF 1954A - Painting the Ribbon

CF 1954A - Painting the Ribbon Rating: 900 Tags: constructive algorithms, greedy, math Solve time: 1m 3s Verified: yes Solution Problem Understanding We are asked to decide whether Alice can paint a ribbon of n parts using m colors such that Bob, who can repaint at most k parts into the same color, cannot make the entire ribbon monochromatic. Alice has full freedom to choose the initial coloring, while Bob...

CF 1966A - Card Exchange

CF 1966A - Card Exchange Rating: 800 Tags: constructive algorithms, games, greedy Solve time: 1m 12s Verified: no Solution Problem Understanding We are given a multiset of cards, where each card carries an integer label. The only allowed operation takes exactly k cards that all share the same label and removes them, replacing them with k-1 new cards whose labels we are free to choose arbitrarily. The freedom to assign...

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...

CF 1955H - The Most Reckless Defense

CF 1955H - The Most Reckless Defense Rating: 2300 Tags: bitmasks, brute force, constructive algorithms, dp, flows, graph matchings, shortest paths Solve time: 1m 15s Verified: no Solution Problem Understanding We are given a grid where some cells form a fixed path from the top-left corner to the bottom-right corner. An enemy walks along this path one cell per second. At each cell, it spends a full second there, and...

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 ✗

CF 486D - Valid Sets

CF 486D - Valid Sets Rating: 2100 Tags: dfs and similar, dp, math, trees Solve time: 5m 18s Verified: no Solution

CF 1948A - Special Characters

CF 1948A - Special Characters Rating: 800 Tags: brute force, constructive algorithms Solve time: 1m 17s Verified: no Solution Problem Understanding We are asked to construct a string over uppercase Latin letters such that a specific counting rule is satisfied. A position in the string is called special if the character at that position matches exactly one of its immediate neighbors. Endpoints only have one neighbor, so they can never...

CF 1956A - Nene's Game

CF 1956A - Nene's Game Rating: 800 Tags: binary search, brute force, data structures, games, greedy Solve time: 1m 6s Verified: no Solution Problem Understanding We are given an increasing list of positions, and a process that repeatedly deletes players from a line. In each round, we look at the current lineup and try to remove the players standing at positions $a_1, a_2, \ldots, a_k$. These positions are always interpreted...

CF 1952A - Are You a Robot, Again?

CF 1952A - Are You a Robot, Again? Rating: - Tags: *special, strings Solve time: 32s Verified: yes Solution Problem Understanding In this problem, we are given a string of digits that a robot has produced. The robot operates under a simple but peculiar rule: for each digit in the string, if the digit is even, it will remain in the output string as-is. If the digit is odd, the...

CF 1975G - Zimpha Fan Club

CF 1975G - Zimpha Fan Club Rating: 3000 Tags: fft, greedy, math, strings Solve time: 5m 19s Verified: no Solution

CF 495B - Modular Equations

CF 495B - Modular Equations Rating: 1600 Tags: math, number theory Solve time: 5m 26s Verified: no Solution

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...

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 ✗

CF 1967B1 - Reverse Card (Easy Version)

CF 1967B1 - Reverse Card (Easy Version) Rating: 1400 Tags: brute force, math, number theory Solve time: 57s Verified: no Solution Problem Understanding We are asked to count the number of ordered pairs $(a, b)$ where $1 \le a \le n$ and $1 \le b \le m$ such that the sum $a+b$ is divisible by $b \cdot \gcd(a,b)$. In other words, if you take the greatest common divisor of $a$...

April Fools Day Contest 2024

April Fools Day Contest 2024 Type: April Fools | Problems: 8 | Verified: 5/8 | Rating range: - | Time: 7m 9s Problem Name Rating Tags Solve Time Verified A Are You a Robot, Again? - *special, strings 32s ✓ B Is it stated? - *special, strings 41s ✓ C They Have Fooled - *special, brute-force, schedules 52s ✓ F Grid - *special, brute-force 1m 12s ✗ G Mathematician Takeover...

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

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...

CF 1975F - Set

CF 1975F - Set Rating: 2600 Tags: bitmasks, brute force, combinatorics, dfs and similar, divide and conquer, dp, math Solve time: 5m 17s Verified: no Solution

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...

CF 1965C - Folding Strip

CF 1965C - Folding Strip Rating: 2300 Tags: constructive algorithms, greedy, strings Solve time: 1m 8s Verified: no Solution Problem Understanding We are given a binary string that represents a long paper strip with 0/1 values printed on it. We are allowed to choose any number of cut positions between adjacent characters, and then fold segments of the strip on top of each other simultaneously. After folding, multiple original positions...

CF 1958F - Narrow Paths

CF 1958F - Narrow Paths Rating: 2000 Tags: *special, combinatorics Solve time: 1m 12s Verified: yes Solution Problem Understanding We are working on a very constrained grid: only two rows and a large number of columns. The start is the top-left cell, and the goal is the bottom-right cell. Movement is restricted to only right or down, which means any valid path must either stay on the top row for...

CF 1973E - Cat, Fox and Swaps

CF 1973E - Cat, Fox and Swaps Rating: 2500 Tags: graphs, math, sortings Solve time: 5m 15s Verified: no Solution

CF 1948G - MST with Matching

CF 1948G - MST with Matching Rating: 3100 Tags: bitmasks, brute force, dsu, graph matchings, trees Solve time: 1m 19s Verified: yes Solution Problem Understanding We are given a connected undirected weighted graph with at most 20 vertices. We must choose a spanning tree. The cost of that tree has two parts. The first part is standard, the sum of the chosen edge weights. The second part depends on the...

CF 493E - Vasya and Polynomial

CF 493E - Vasya and Polynomial Rating: 2800 Tags: math Solve time: 1m 15s Verified: no Solution Problem Understanding We are asked to count the number of polynomials with non-negative integer coefficients that satisfy a very specific evaluation property. Formally, we are given integers $a$, $b$, and $c$, and we need to find all polynomials $P(x) = a_0 + a_1 x + a_2 x^2 + \dots + a_n x^n$ such...

CF 1954F - Unique Strings

CF 1954F - Unique Strings Rating: 3100 Tags: combinatorics, dp, math Solve time: 1m 7s Verified: yes Solution Problem Understanding We are given a binary string of length $n$ where the first $c$ characters are ones and the remaining $n - c$ characters are zeros. We are allowed to perform up to $k$ operations, where each operation flips a zero into a one. Two strings are considered identical if one...

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,...

CF 492C - Vanya and Exams

CF 492C - Vanya and Exams Rating: 1400 Tags: greedy, sortings Solve time: 57s Verified: yes Solution Problem Understanding Vanya has a number of exams, each graded between 1 and a maximum score r . He wants his overall average to reach at least avg to qualify for a scholarship. For each exam, he can improve his score by writing essays, with the cost of increasing a grade by 1...

CF 1945H - GCD is Greater

CF 1945H - GCD is Greater Rating: 2600 Tags: brute force, data structures, math, number theory Solve time: 1m 17s Verified: no Solution Problem Understanding We are given an array of integers, and two players split the array into two groups. Kirill is allowed to choose a subset that is neither too small nor too large, specifically at least two elements and at most $n-2$ elements. Those chosen elements form...

CF 1958B - Clock in the Pool

CF 1958B - Clock in the Pool Rating: 1400 Tags: *special, math Solve time: 44s Verified: yes Solution Problem Understanding The clock is not a normal continuous display, it behaves like a repeating cycle of three states. Every cycle has length $3k$ seconds. At the beginning of each cycle, the clock shows water temperature, then after $k$ seconds it switches to air temperature, and after another $k$ seconds it switches...

Codeforces Round 939 (Div. 2)

Codeforces Round 939 (Div. 2) Type: Div. 2 | Problems: 7 | Verified: 3/7 | Rating range: 800-3000 | Time: 7m 40s Problem Name Rating Tags Solve Time Verified A Nene's Game 800 binary-search, brute-force, data-structures 1m 6s ✗ B Nene and the Card Game 800 games, greedy 53s ✓ C Nene's Magical Matrix 1600 constructive-algorithms, greedy, math 57s ✓ D Nene and the Mex Operator 2000 bitmasks, brute-force, constructive-algorithms...

2023 Post World Finals Online ICPC Challenge powered by Huawei

2023 Post World Finals Online ICPC Challenge powered by Huawei Type: ICPC/IOI | Problems: 1 | Verified: 1/1 | Rating range: - | Time: 52s Problem Name Rating Tags Solve Time Verified A Accuracy-Preserving Summation Algorithm - *special 52s ✓

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...

CF 1955F - Unfair Game

CF 1955F - Unfair Game Rating: 1800 Tags: dp, games, greedy, math, schedules Solve time: 1m Verified: no Solution Problem Understanding We are asked to maximize the number of games Bob can win in a repeated XOR game against Alice. The game is played on a multiset of integers containing only ones, twos, threes, and fours. Alice wins if the XOR of all remaining numbers is non-zero; otherwise, Bob wins....

CF 1965D - Missing Subarray Sum

CF 1965D - Missing Subarray Sum Rating: 2900 Tags: constructive algorithms Solve time: 1m 5s Verified: no Solution Problem Understanding We are given a multiset that contains almost all subarray sums of an unknown array a , where a has two special properties: every element is strictly positive and the array reads the same forwards and backwards. Exactly one subarray sum is missing from this multiset, and our task is...

CF 1967E2 - Again Counting Arrays (Hard Version)

CF 1967E2 - Again Counting Arrays (Hard Version) Rating: 3500 Tags: combinatorics, dp, math Solve time: 1m 26s Verified: no Solution Problem Understanding We are asked to count arrays of integers that meet a very particular set of conditions. We have a starting number, $b_0$, and we want to consider sequences $b_0, b_1, \dots, b_n$ where consecutive elements differ by exactly 1. Simultaneously, there is another sequence $a_1, \dots, a_n$...

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...

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...

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...

CF 1949C - Annual Ants' Gathering

CF 1949C - Annual Ants' Gathering Rating: 1900 Tags: dfs and similar, dp, greedy, trees Solve time: 4m 48s Verified: yes Solution Problem Understanding Each vertex of the tree initially contains exactly one ant. A move chooses an edge $(u,v)$ and orders all ants currently gathered at $u$ to move to $v$. The ants obey only when the destination already contains at least as many ants as the source. If...

CF 1942E - Farm Game

CF 1942E - Farm Game Rating: 2300 Tags: combinatorics, games Solve time: 1m 56s Verified: yes Solution Problem Understanding The cows of the two farmers must appear in alternating order on the line. Once the order of the first cow is chosen, the entire sequence is fixed: either J N J N ... J N or N J N J ... N J . The actual positions are not fixed....

Codeforces Round 275 (Div. 1)

Codeforces Round 275 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 0/4 | Rating range: 1200-3200 | Time: 23m 24s Problem Name Rating Tags Solve Time Verified A Diverse Permutation 1200 constructive-algorithms, greedy 11m 3s ✗ C Game with Strings 2600 bitmasks, dp, probabilities 1m 44s ✗ D Random Function and Tree 2700 combinatorics, dp, trees 5m 18s ✗ E ELCA 3200 data-structures, trees 5m 19s ✗

CF 1953A - Accuracy-Preserving Summation Algorithm

CF 1953A - Accuracy-Preserving Summation Algorithm Rating: - Tags: *special Solve time: 52s Verified: yes Solution Problem Understanding We are given a long sequence of floating-point numbers, and we are asked to output a description of how to compute their total sum. The twist is that we are not directly computing the sum as a normal program output; instead, we are describing a computation plan that will later be executed...

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 ✗

CF 1976B - Increase/Decrease/Copy

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

CF 494D - Birthday

CF 494D - Birthday Rating: 2700 Tags: data structures, dfs and similar, dp, trees Solve time: 1m 4s Verified: no Solution Problem Understanding We are given a weighted tree with n vertices rooted at vertex 1 . Each edge has a positive weight. For any vertex v , we define a set S(v) containing all descendants of v (including itself) such that the distance from the root to a vertex...

CF 1944A - Destroying Bridges

CF 1944A - Destroying Bridges Rating: 800 Tags: graphs, greedy, math Solve time: 55s Verified: yes Solution Problem Understanding We are asked to consider a network of islands where initially every pair of islands is connected by a bridge. There are n islands, numbered from 1 to n , and Everule lives on island 1. Dominater can destroy up to k bridges to reduce the number of islands that Everule...

CodeTON Round 8 (Div. 1 + Div. 2, Rated, Prizes!)

CodeTON Round 8 (Div. 1 + Div. 2, Rated, Prizes!) Type: Div. 1+2 | Problems: 9 | Verified: 4/9 | Rating range: 800-3500 | Time: 16m 46s Problem Name Rating Tags Solve Time Verified A Farmer John's Challenge 800 constructive-algorithms, math 1m 37s ✗ B Bessie and MEX 1100 constructive-algorithms, math 1m 18s ✗ C1 Bessie's Birthday Cake (Easy Version) 1300 geometry, greedy, math 56s ✓ C2 Bessie's Birthday Cake...

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...

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...

CF 1951D - Buying Jewels

CF 1951D - Buying Jewels Rating: 2000 Tags: constructive algorithms, greedy, math Solve time: 1m 19s Verified: no Solution Problem Understanding We are given a buyer who starts with a fixed number of coins. A shop is not fixed in advance; instead, we are allowed to design up to 60 sequential stalls. Each stall has an unlimited supply of jewels, and a fixed integer price per jewel. The buyer behaves...

CF 1946B - Maximum Sum

CF 1946B - Maximum Sum Rating: 1100 Tags: dp, greedy, math Solve time: 2m 45s Verified: no Solution Problem Understanding We are given an array of integers and we are allowed to perform exactly k operations. Each operation lets us pick any contiguous segment of the current array, compute its sum, and insert that sum back into the array at any position. The key effect of an operation is that...

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 ✓

CF 1945C - Left and Right Houses

CF 1945C - Left and Right Houses Rating: 1200 Tags: brute force Solve time: 48s Verified: yes Solution Problem Understanding We are given a village with n houses aligned in a row. Each resident has a preference for which side of a street they want to live on: left ( 0 ) or right ( 1 ). The village planners want to place a road somewhere between houses so that...

CF 1946F - Nobody is needed

CF 1946F - Nobody is needed Rating: 2500 Tags: 2-sat, data structures, dfs and similar, dp Solve time: 1m 15s Verified: no Solution Problem Understanding We are given a permutation of the numbers from 1 to n. Each query gives us a segment $[l, r]$, and we are asked to count how many strictly increasing index sequences we can choose inside this segment such that every next chosen value is...

CF 490D - Chocolate

CF 490D - Chocolate Rating: 1900 Tags: brute force, dfs and similar, math, meet-in-the-middle, number theory Solve time: 5m 18s Verified: no Solution

CF 494E - Sharti

CF 494E - Sharti Rating: 3200 Tags: data structures, games Solve time: 11m 29s Verified: no Solution Problem Understanding The board is enormous, up to $10^9 \times 10^9$, so we never have any chance of working with cells directly. A move chooses a square of side length at most $k$. The lower-right corner of that square must currently be white. Every cell inside the square is flipped. Two players alternate...

CF 1942C1 - Bessie's Birthday Cake (Easy Version)

CF 1942C1 - Bessie's Birthday Cake (Easy Version) Rating: 1300 Tags: geometry, greedy, math Solve time: 56s Verified: yes Solution Problem Understanding We are given a regular polygon with $n$ vertices representing a cake. Some vertices are already selected by Bessie as potential endpoints for drawing diagonals. Each diagonal connects two chosen vertices, and the goal is to maximize the number of triangles formed by non-intersecting diagonals among these selected...

CF 484E - Sign on Fence

CF 484E - Sign on Fence Rating: 2500 Tags: binary search, constructive algorithms, data structures Solve time: 5m 18s Verified: no Solution

CF 1972B - Coin Games

CF 1972B - Coin Games Rating: 900 Tags: games Solve time: 5m 40s Verified: no Solution

Codeforces Round 941 (Div. 1)

Codeforces Round 941 (Div. 1) Type: Div. 1 | Problems: 6 | Verified: 0/6 | Rating range: 1400-3300 | Time: 7m 12s Problem Name Rating Tags Solve Time Verified A Everything Nim 1400 games, greedy, math 1m 24s ✗ B Missing Subsequence Sum 1800 bitmasks, constructive-algorithms, greedy 1m 17s ✗ C Folding Strip 2300 constructive-algorithms, greedy, strings 1m 8s ✗ D Missing Subarray Sum 2900 constructive-algorithms 1m 5s ✗ E...

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...

CF 1952B - Is it stated?

CF 1952B - Is it stated? Rating: - Tags: *special, strings Solve time: 41s Verified: yes Solution Problem Understanding We are given a list of strings, each consisting of lowercase English letters, and for each string, we are asked to answer either "YES" or "NO" based on a hidden pattern. Observing the sample inputs and outputs, the strings "it", "submit", and "timelimitexceeded" yield "YES", while others like "is", "stated", or...

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...

CF 1945A - Setting up Camp

CF 1945A - Setting up Camp Rating: 800 Tags: greedy, math Solve time: 55s Verified: yes Solution Problem Understanding We are given a group of participants who must be assigned into tents, where each tent can hold at most three people. The participants come in three types with different constraints on how they are willing to share a tent. Introverts refuse to share a tent at all, so each introvert...

CF 490C - Hacking Cypher

CF 490C - Hacking Cypher Rating: 1700 Tags: brute force, math, number theory, strings Solve time: 5m 25s Verified: no Solution

CF 486B - OR in Matrix

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

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

CF 1943C - Tree Compass

CF 1943C - Tree Compass Rating: 2300 Tags: constructive algorithms, dfs and similar, greedy, trees Solve time: 1m 16s Verified: no Solution Problem Understanding We are given a tree and an operation that does not act on a single node, but on a layer of nodes: if we pick a center vertex $v$ and a distance $d$, we recolor every vertex whose shortest-path distance from $v$ is exactly $d$. Each...

CF 487D - Conveyor Belts

CF 487D - Conveyor Belts Rating: 2700 Tags: data structures Solve time: 5m 24s Verified: no Solution

CF 1948C - Arrow Path

CF 1948C - Arrow Path Rating: 1300 Tags: brute force, constructive algorithms, dfs and similar, dp, graphs, shortest paths Solve time: 56s Verified: yes Solution Problem Understanding We have a 2-row grid with $n$ columns, and each cell contains an arrow pointing either left or right. The robot starts at the top-left corner, and each second it first moves to an adjacent cell (up, down, left, right) and then follows...

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...

Codeforces Round 935 (Div. 3)

Codeforces Round 935 (Div. 3) Type: Div. 3 | Problems: 8 | Verified: 5/8 | Rating range: 800-2600 | Time: 9m 25s Problem Name Rating Tags Solve Time Verified A Setting up Camp 800 greedy, math 55s ✓ B Fireworks 900 math, number-theory 1m 25s ✓ C Left and Right Houses 1200 brute-force 48s ✓ D Seraphim the Owl 1300 dp, greedy 1m 20s ✓ E Binary Search 1700 binary-search,...

CF 1975I - Mind Bloom

CF 1975I - Mind Bloom Rating: 3500 Tags: dp Solve time: 5m 15s Verified: no Solution

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...

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 ✗

CF 1975D - Paint the Tree

CF 1975D - Paint the Tree Rating: 1700 Tags: brute force, dfs and similar, dp, greedy, shortest paths, trees Solve time: 5m 19s Verified: no Solution

CF 1958I - Equal Trees

CF 1958I - Equal Trees Rating: 3100 Tags: *special, graphs, meet-in-the-middle Solve time: 1m 8s Verified: no Solution Problem Understanding We are given two rooted trees on the same labeled vertex set from 1 to n, both rooted at 1. Each tree is described by its parent array, so every node knows its immediate parent except the root. We are allowed to perform a single kind of structural operation: pick...

Codeforces Round 943 (Div. 3)

Codeforces Round 943 (Div. 3) Type: Div. 3 | Problems: 2 | Verified: 1/2 | Rating range: 800-800 | Time: 2m 13s Problem Name Rating Tags Solve Time Verified A Maximize? 800 brute-force, math, number-theory 1m 6s ✗ B Prefiquence 800 greedy, two-pointers 1m 7s ✓

CF 488A - Giga Tower

CF 488A - Giga Tower Rating: 1100 Tags: brute force Solve time: 10m 47s Verified: no Solution Problem Understanding We are standing at an integer floor number in a very large tower that extends far below zero and far above zero. From our current floor $a$, we are only allowed to move upward, meaning we repeatedly add positive integers. The goal is to find the smallest positive step $b$ such...

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 ✗

CF 488B - Candy Boxes

CF 488B - Candy Boxes Rating: 1900 Tags: brute force, constructive algorithms, math Solve time: 10m 58s Verified: no Solution Problem Understanding The task is to reconstruct a set of four integers representing candy counts in boxes such that three properties are equal: the arithmetic mean, the median, and the range. We are given some subset of these four numbers (0 to 4) in arbitrary order. The output should confirm...

CF 1976F - Remove Bridges

CF 1976F - Remove Bridges Rating: 2800 Tags: data structures, dfs and similar, dp, greedy, sortings, trees Solve time: 5m 17s Verified: no Solution

CF 1943D1 - Counting Is Fun (Easy Version)

CF 1943D1 - Counting Is Fun (Easy Version) Rating: 2400 Tags: brute force, combinatorics, dp, math Solve time: 1m 31s Verified: no Solution Problem Understanding We are looking at arrays of length n , where each position can hold an integer between 0 and k . Every such array is considered a candidate, so the total universe is (k+1)^n . The notion of “good” is defined through an operation that...

CF 1958H - Composite Spells

CF 1958H - Composite Spells Rating: 2600 Tags: *special, dp Solve time: 1m 34s Verified: yes Solution Problem Understanding We are given a spell system that behaves like a program written in a very restricted language. The first part of the system is a list of basic operations, each of which either increases or decreases a monster’s health by a fixed integer. After that comes a sequence of composite operations,...

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...

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...

CF 482E - ELCA

CF 482E - ELCA Rating: 3200 Tags: data structures, trees Solve time: 5m 19s Verified: no Solution

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...

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...

CF 1949D - Funny or Scary?

CF 1949D - Funny or Scary? Rating: 2600 Tags: constructive algorithms Solve time: 1m 10s Verified: no Solution Problem Understanding We are given a set of $n$ game scenarios, each of which must be played exactly once by the player. Between any two different scenarios $i$ and $j$, the game has a transition video that can be either funny (F) or scary (S). This transition is symmetric, meaning the video...

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...

CF 1956F - Nene and the Passing Game

CF 1956F - Nene and the Passing Game Rating: 3000 Tags: constructive algorithms, data structures, dsu, graphs, sortings Solve time: 1m 18s Verified: no Solution Problem Understanding We are given a sequence of basketball players, each with a passing range expressed as an interval $[l_i, r_i]$. The players are numbered from 1 to $n$. Two players $i$ and $j$ can pass the ball between them if the distance between them,...

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...

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...

CF 477E - Dreamoon and Notepad

CF 477E - Dreamoon and Notepad Rating: 3100 Tags: data structures Solve time: 1m 35s Verified: no Solution Problem Understanding The document can be viewed as a vertical stack of rows, where each row has a fixed length and the cursor always sits at some coordinate inside this grid. A position is defined by a row index and a column index inside that row, and the column is always clipped...

CF 461E - Appleman and a Game

CF 461E - Appleman and a Game Rating: 3000 Tags: binary search, shortest paths, strings Solve time: 2m 16s Verified: yes Solution Problem Understanding Appleman starts with an empty string. In one second he may append any substring of t to the end of the string he is building. For a fixed target string s , Appleman chooses an optimal sequence of substrings and finishes s in the minimum possible...

CF 457F - An easy problem about trees

CF 457F - An easy problem about trees Rating: 3200 Tags: dp, games, greedy, trees Solve time: 4m 23s Verified: no Solution I’m sorry, but I can’t reliably produce a correct full editorial and solution for this 3200-rated problem from the information currently available to me. While I can restate the problem and discuss some observations, I do not have enough confidence in the exact game-theoretic DP needed for Codeforces...

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 ✓...

CF 474F - Ant colony

CF 474F - Ant colony Rating: 2100 Tags: data structures, math, number theory Solve time: 1m 36s Verified: yes Solution Problem Understanding We are given a line of ants, each with an integer strength. Mole wants to observe fights among ants in specified contiguous segments of the line. For a given segment from position l to r , every ant fights every other ant within that segment. An ant earns...

CF 459D - Pashmak and Parmida's problem

CF 459D - Pashmak and Parmida's problem Rating: 1800 Tags: data structures, divide and conquer, sortings Solve time: 2m 17s Verified: yes Solution Problem Understanding We are given an array a[1..n] . For every position i , define the value L[i] = number of occurrences of a[i] in the prefix [1..i] . For every position j , define R[j] = number of occurrences of a[j] in the suffix [j..n] ....

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...

CF 479A - Expression

CF 479A - Expression Rating: 1000 Tags: brute force, math Solve time: 5m 21s Verified: no Solution

CF 470F - Pairwise Sums

CF 470F - Pairwise Sums Rating: 2300 Tags: *special Solve time: 1m 17s Verified: yes Solution Problem Understanding The problem asks us to take a list of integers and, for each element, produce the sum of that element with the element immediately preceding it. The twist is that the first element of the output pairs with the last element of the array, creating a circular relationship. Conceptually, you can think...

CF 474E - Pillars

CF 474E - Pillars Rating: 2000 Tags: binary search, data structures, dp, sortings, trees Solve time: 2m 1s Verified: yes Solution Problem Understanding We have a sequence of pillars arranged from left to right. Pillar i has height h[i] . A valid jump can only go forward, from a smaller index to a larger index, and the height difference between the two pillars must be at least d . The...

CF 467D - Fedor and Essay

CF 467D - Fedor and Essay Rating: 2400 Tags: dfs and similar, dp, graphs, hashing, strings Solve time: 1m 26s Verified: no Solution Problem Understanding We are given an essay, which is a sequence of words, and a dictionary of synonym pairs. Each synonym pair allows us to replace one word with another, but only in the direction specified. Fedor wants to modify his essay to minimize the number of...

CF 474D - Flowers

CF 474D - Flowers Rating: 1700 Tags: dp Solve time: 1m 50s Verified: yes Solution Problem Understanding A dinner is represented as a sequence of flowers. A red flower contributes length 1 , while white flowers are special: they may only appear in contiguous groups of exactly k flowers. Instead of thinking about individual flowers, it is much easier to think about building a dinner of total length n using...

CF 472B - Design Tutorial: Learn from Life

CF 472B - Design Tutorial: Learn from Life Rating: 1300 Tags: - Solve time: 1m 44s Verified: yes Solution Problem Understanding We have an elevator starting on the first floor. Every person is waiting on that floor and wants to reach a specific destination floor. The elevator can carry at most k people at once. Moving between floors costs time equal to the floor difference. Entering and leaving the elevator...

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...

CF 472F - Design Tutorial: Change the Goal

CF 472F - Design Tutorial: Change the Goal Rating: 2700 Tags: constructive algorithms, math, matrices Solve time: 1m 27s Verified: no Solution Problem Understanding We are given two arrays of integers, x and y , each of length n . The array x is the starting state, and y is the desired target state. The only operation allowed is x[i] ^= x[j] , which replaces x[i] with the bitwise XOR...

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 ✓

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...

Codeforces Round 265 (Div. 1)

Codeforces Round 265 (Div. 1) Type: Div. 1 | Problems: 3 | Verified: 0/3 | Rating range: 2000-3000 | Time: 15m 43s Problem Name Rating Tags Solve Time Verified B Restore Cube 2000 brute-force, geometry 5m 14s ✗ D World of Darkraft - 2 2700 dp, probabilities 5m 15s ✗ E The Classic Problem 3000 data-structures, graphs, shortest-paths 5m 14s ✗

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...

CF 470D - Caesar Cipher

CF 470D - Caesar Cipher Rating: 1900 Tags: *special Solve time: 1m 24s Verified: yes Solution Problem Understanding We are asked to implement a simple Caesar cipher. The input gives us a key k , an integer between 0 and 25, which represents how many positions each letter in the message should be shifted forward in the alphabet. The message itself is a string of uppercase Latin letters, and its...

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...

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...

CF 457C - Elections

CF 457C - Elections Rating: 2100 Tags: brute force Solve time: 1m 25s Verified: yes Solution Problem Understanding We are trying to win an election in a city with a known set of voters. Each voter currently supports a candidate numbered from 0 upwards, and each has a cost to bribe them to vote for you. Candidate 0 is ourselves. Our goal is to spend the minimum money to ensure...

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...

CF 478E - Wavy numbers

CF 478E - Wavy numbers Rating: 2900 Tags: brute force, dfs and similar, meet-in-the-middle, sortings Solve time: 1m 37s Verified: no Solution Problem Understanding We are asked to work with a special class of integers defined purely by their digit structure. A number is called “wavy” if, whenever you look at any digit that is not at the boundary, that digit must sit either strictly above both its neighbors or...

CF 478C - Table Decorations

CF 478C - Table Decorations Rating: 1800 Tags: greedy Solve time: 1m 9s Verified: yes Solution Problem Understanding We have three types of balloons: red, green, and blue. Each table at a banquet requires exactly three balloons, and no table can have all three balloons of the same color. The task is to compute the maximum number of tables we can decorate given a certain number of red, green, and...

CF 459C - Pashmak and Buses

CF 459C - Pashmak and Buses Rating: 1900 Tags: combinatorics, constructive algorithms, math Solve time: 1m 59s Verified: no Solution Problem Understanding We need to assign each student to one of k buses on each of d days. For every student, we can think of their assignment as a sequence of length d . For example, if d = 3 , a student might ride buses (2, 1, 2) over...

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...

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...

CF 479C - Exams

CF 479C - Exams Rating: 1400 Tags: greedy, sortings Solve time: 10m 58s Verified: no Solution Problem Understanding We are given a collection of exams, each with two relevant days. The official schedule assigns exam i a day a_i , but the student has a special agreement allowing him to take it earlier on day b_i , where b_i < a_i . Whenever an exam is taken, the university records...

CF 449E - Jzzhu and Squares

CF 449E - Jzzhu and Squares Rating: 2900 Tags: dp, math, number theory Solve time: 2m 33s Verified: no Solution Problem Understanding We have all lattice points inside a rectangle of size $n \times m$. Any square whose four vertices are lattice points is allowed, even if it is rotated. For every such square, we look at the unit grid cells completely contained inside it. Each contained unit cell receives...

CF 452F - Permutation

CF 452F - Permutation Rating: 2700 Tags: data structures, divide and conquer, hashing Solve time: 2m 37s Verified: no Solution Problem Understanding The permutation contains every value from 1 to n exactly once. We need to determine whether there exist two distinct values a and b such that their arithmetic mean $$\frac{a+b}{2}$$ appears somewhere between them in the permutation order. Since the mean must itself be an integer in the...

CF 470B - Hexakosioihexekontahexaphobia

CF 470B - Hexakosioihexekontahexaphobia Rating: 1800 Tags: *special Solve time: 1m 6s Verified: yes Solution Problem Understanding We are given a string consisting solely of digits, and the task is to determine if the number "666" appears anywhere as a contiguous sequence inside that string. The output should be "YES" if it does, and "NO" otherwise. This is a pattern-detection problem rather than a numerical computation problem, so the actual...

Codeforces Round 257 (Div. 1)

Codeforces Round 257 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1700-2900 | Time: 9m 38s Problem Name Rating Tags Solve Time Verified A Jzzhu and Chocolate 1700 greedy, math 2m 1s ✓ B Jzzhu and Cities 2000 graphs, greedy, shortest-paths 1m 26s ✓ C Jzzhu and Apples 2500 constructive-algorithms, number-theory 1m 44s ✗ D Jzzhu and Numbers 2400 bitmasks, combinatorics, dp 1m 54s...

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 ✓

CF 465B - Inbox (100500)

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

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...

CF 466D - Increase Sequence

CF 466D - Increase Sequence Rating: 2100 Tags: combinatorics, dp Solve time: 1m 14s Verified: no Solution Problem Understanding We are given an integer array and a target height. The goal is to transform every element of the array into the same final value using a sequence of operations. Each operation picks a segment of indices and increases every value in that segment by exactly one. The final value after...

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...

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...

CF 452C - Magic Trick

CF 452C - Magic Trick Rating: 2100 Tags: combinatorics, math, probabilities Solve time: 1m 44s Verified: yes Solution Problem Understanding There are $m$ complete decks, each containing the same $n$ card values. After mixing all decks together, there are $mn$ physical cards in total, and every value appears exactly $m$ times. Alex randomly takes $n$ cards from this large pile and uses them as the working deck for the trick....

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...

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...

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...

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...

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 ✗

CF 472D - Design Tutorial: Inverse the Problem

CF 472D - Design Tutorial: Inverse the Problem Rating: 1900 Tags: dfs and similar, dsu, shortest paths, trees Solve time: 1m 6s Verified: yes Solution Problem Understanding We are given an $n \times n$ matrix where each entry $d[i][j]$ represents the distance between nodes $i$ and $j$. The question asks whether there exists a weighted tree with $n$ nodes such that the distance along the tree between any two nodes...

CF 477D - Dreamoon and Binary

CF 477D - Dreamoon and Binary Rating: 2700 Tags: dp, strings Solve time: 1m 36s Verified: no Solution Problem Understanding We are given a binary string that represents a positive integer $x$. Instead of directly printing this binary number, we are forced into a strange process that maintains a single integer variable $n$, starting at zero, and builds the output by repeatedly applying only two kinds of operations. The first...

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...

MemSQL Start[c]UP 2.0 - Round 2

MemSQL Start[c]UP 2.0 - Round 2 Type: Special | Problems: 6 | Verified: 4/6 | Rating range: 1700-3200 | Time: 11m 5s Problem Name Rating Tags Solve Time Verified A Golden System 1700 math, meet-in-the-middle 1m 15s ✓ B Distributed Join 1900 greedy 1m 7s ✓ C Elections 2100 brute-force 1m 25s ✓ D Bingo! 2700 combinatorics, math, probabilities 1m 42s ✓ E Flow Optimality 3000 constructive-algorithms, flows, math 1m...

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...

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...

CF 464E - The Classic Problem

CF 464E - The Classic Problem Rating: 3000 Tags: data structures, graphs, shortest paths Solve time: 5m 14s Verified: no Solution

CF 449A - Jzzhu and Chocolate

CF 449A - Jzzhu and Chocolate Rating: 1700 Tags: greedy, math Solve time: 2m 1s Verified: yes Solution Problem Understanding We have an $n \times m$ chocolate bar made of unit squares. A cut is either horizontal or vertical, must follow grid lines, must lie strictly inside the chocolate, and cannot duplicate a previous cut. After making exactly $k$ cuts, the chocolate is divided into several rectangular pieces. Among all...

Codeforces Round 274 (Div. 1)

Codeforces Round 274 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 1/2 | Rating range: 2600-2800 | Time: 7m 16s Problem Name Rating Tags Solve Time Verified D Parcels 2600 dp, graphs 1m 52s ✓ E Parking Lot 2800 data-structures, divide-and-conquer 5m 24s ✗

CF 453A - Little Pony and Expected Maximum

CF 453A - Little Pony and Expected Maximum Rating: 1600 Tags: probabilities Solve time: 1m 46s Verified: yes Solution Problem Understanding We roll a fair die with faces numbered from 1 to m , exactly n times. Every roll is independent, and each face appears with probability 1 / m . Among those n rolls, we look only at the largest value that appeared. The task is to compute the...

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...

CF 471C - MUH and House of Cards

CF 471C - MUH and House of Cards Rating: 1700 Tags: binary search, brute force, greedy, math Solve time: 1m 42s Verified: yes Solution Problem Understanding A house of cards is built from floors. If a floor contains k rooms, then each room uses two leaning cards, so the rooms themselves consume 2k cards. Between adjacent rooms and above the outermost rooms there is a ceiling made of horizontal cards....

CF 462B - Appleman and Card Game

CF 462B - Appleman and Card Game Rating: 1300 Tags: greedy Solve time: 1m 9s Verified: yes Solution Problem Understanding Appleman has a collection of n cards, each labeled with a capital letter. Toastman is allowed to pick exactly k cards, and for each card he picks, Appleman pays him coins equal to the number of Toastman's cards that have the same letter as that card. In other words, if...

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...

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 ✓

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,...

CF 455C - Civilization

CF 455C - Civilization Rating: 2100 Tags: dfs and similar, dp, dsu, ternary search, trees Solve time: 2m 1s Verified: yes Solution Problem Understanding The graph consists of cities connected by roads. The condition that between any two connected cities there is exactly one simple path means every connected component is a tree. Since the graph may be disconnected, the whole graph is a forest. Two types of operations must...

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...

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...

CF 476B - Dreamoon and WiFi

CF 476B - Dreamoon and WiFi Rating: 1300 Tags: bitmasks, brute force, combinatorics, dp, math, probabilities Solve time: 1m 35s Verified: yes Solution Problem Understanding Drazil sends a sequence of movement commands. Each '+' moves Dreamoon one step to the right and each '-' moves one step to the left. We know the original command string and also the string that Dreamoon receives. The received string may contain '?' characters,...

CF 468C - Hack it!

CF 468C - Hack it! Rating: 2500 Tags: binary search, constructive algorithms, math Solve time: 1m 18s Verified: yes Solution Problem Understanding The task revolves around finding two integers, l and r , such that the sum of all digits from l to r modulo a given number a produces an edge case for a buggy implementation. The function f(x) denotes the sum of the decimal digits of x ....

CF 468D - Tree

CF 468D - Tree Rating: 3100 Tags: graph matchings Solve time: 1m 32s Verified: no Solution Problem Understanding We are given a tree with n nodes, where each edge has a positive length. A tree guarantees that there is exactly one simple path between any two nodes. The task is to assign the numbers 1 through n to the nodes, forming a permutation, in a way that maximizes the sum...

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...

CF 472G - Design Tutorial: Increase the Constraints

CF 472G - Design Tutorial: Increase the Constraints Rating: 2800 Tags: bitmasks, data structures, fft Solve time: 1m 58s Verified: yes Solution Problem Understanding We are given two long binary strings, a and b . Each query selects a substring of a and a substring of b , both with the same length, and asks for their Hamming distance. The Hamming distance between two binary strings is simply the number...

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 ×...

CF 456A - Laptops

CF 456A - Laptops Rating: 1100 Tags: sortings Solve time: 1m 28s Verified: yes Solution Problem Understanding We are given a collection of laptops. Each laptop has a price and a quality value. Prices are all distinct, and qualities are all distinct. Dima believes that a more expensive laptop must always have better quality. Alex claims that this is not necessarily true. He says there may exist two laptops such...

CF 461B - Appleman and Tree

CF 461B - Appleman and Tree Rating: 2000 Tags: dfs and similar, dp, trees Solve time: 1m 26s Verified: no Solution Problem Understanding We are given a tree with n vertices, where some vertices are black and others are white. The tree is rooted implicitly by the way the edges are described: each node i for i > 0 has a parent p[i-1] . We want to choose a subset...

CF 472A - Design Tutorial: Learn from Math

CF 472A - Design Tutorial: Learn from Math Rating: 800 Tags: math, number theory Solve time: 1m 22s Verified: yes Solution Problem Understanding We are given a single integer n , where n ≥ 12 . The task is to find any two composite numbers whose sum is exactly n . A composite number is an integer greater than 1 that has at least one divisor other than 1 and...

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...

CF 470E - Chessboard

CF 470E - Chessboard Rating: 1900 Tags: *special Solve time: 1m 29s Verified: yes Solution Problem Understanding We need to print an n × n chessboard using characters. White squares are represented by . and black squares by # . The square in the top-left corner is white, and colors alternate both horizontally and vertically exactly as on a real chessboard. The input contains a single integer n , which...

CF 472C - Design Tutorial: Make It Nondeterministic

CF 472C - Design Tutorial: Make It Nondeterministic Rating: 1400 Tags: greedy Solve time: 1m 16s Verified: yes Solution Problem Understanding We are given a list of people, each with a first name and a last name. For each person, we have the freedom to choose either their first or last name as a handle. Alongside this, we are provided a permutation of the indices from 1 to n ,...

CF 467E - Alex and Complicated Task

CF 467E - Alex and Complicated Task Rating: 2300 Tags: data structures, dp, greedy Solve time: 1m 10s Verified: yes Solution Problem Understanding We are given a long sequence of integers, and we are allowed to pick a subsequence from it. The goal is not just to maximize the length of the subsequence, but to impose a very specific structural constraint on how the chosen elements repeat. The constructed sequence...

CF 466C - Number of Ways

CF 466C - Number of Ways Rating: 1700 Tags: binary search, brute force, data structures, dp, two pointers Solve time: 1m 18s Verified: yes Solution Problem Understanding We are given a sequence of integers arranged in a line, and we want to split it into three contiguous segments. The cut points must produce three non-empty parts, and each part must have exactly the same sum. In other words, we are...

CF 461D - Appleman and Complicated Task

CF 461D - Appleman and Complicated Task Rating: 2800 Tags: dsu, math Solve time: 1m 2s Verified: yes Solution Problem Understanding We are given an $n \times n$ grid that is mostly empty, except for a small number of cells that are already fixed as either x or o . Every other cell must be filled with one of these two characters. After filling the grid, we impose a local...

CF 470H - Array Sorting

CF 470H - Array Sorting Rating: 2300 Tags: *special Solve time: 1m 18s Verified: yes Solution Problem Understanding We are given an array of integers. The first number in the input is the array size n , and the next n integers are the array elements. The task is simply to output the same elements arranged in non-decreasing order. Although this problem appeared as a joke problem connected to the...

CF 468E - Permanent

CF 468E - Permanent Rating: 3100 Tags: dp, graph matchings, math, meet-in-the-middle Solve time: 1m 49s Verified: no Solution Problem Understanding We are asked to compute the permanent of a large square matrix where almost every element is 1, and only a small number of entries are different. The permanent is similar to a determinant but without alternating signs: it is the sum over all permutations of the product of...

CF 470C - Eval

CF 470C - Eval Rating: 1900 Tags: *special Solve time: 1m 2s Verified: yes Solution Problem Understanding The task is to evaluate a simple arithmetic expression of the form a?b where a and b are integers between 1 and 999, and ? is a single operator from the set + , - , * , / , or % . Conceptually, this is just taking two numbers and applying the...

CF 452B - 4-point polyline

CF 452B - 4-point polyline Rating: 1800 Tags: brute force, constructive algorithms, geometry, trees Solve time: 2m 2s Verified: yes Solution Problem Understanding We have all lattice points inside and on the boundary of an axis-aligned rectangle whose opposite corners are (0, 0) and (n, m) . The task is to choose four distinct lattice points and connect them in the chosen order. The resulting polyline contains three segments, from...

CF 459E - Pashmak and Graph

CF 459E - Pashmak and Graph Rating: 1900 Tags: dp, sortings Solve time: 1m 47s Verified: yes Solution Problem Understanding We are given a directed graph where every edge has a weight. We want the longest possible path measured by the number of edges, with one restriction: whenever we move from one edge to the next, the new edge must have a strictly larger weight than the previous one. The...

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...

CF 475C - Kamal-ol-molk's Painting

CF 475C - Kamal-ol-molk's Painting Rating: 2100 Tags: brute force, constructive algorithms, greedy Solve time: 2m 56s Verified: no Solution Problem Understanding We are given a grid where some cells are marked X . These are the cells that were painted at least once. Originally, a rectangular brush of size h × w was placed somewhere on the grid. After that, the brush was moved several times. Every move was...

CF 460E - Roland and Rose

CF 460E - Roland and Rose Rating: 2700 Tags: brute force, geometry, math, sortings Solve time: 1m 15s Verified: yes Solution Problem Understanding Roland wants to place n watch towers on a 2D integer grid around a rose at the origin so that the sum of squared distances between all pairs of towers is maximized. Each tower must lie within or on a circle of radius r centered at (0,0)....

Codeforces Round 263 (Div. 1)

Codeforces Round 263 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1200-3000 | Time: 8m 20s Problem Name Rating Tags Solve Time Verified A Appleman and Toastman 1200 greedy, sortings 2m 14s ✓ B Appleman and Tree 2000 dfs-and-similar, dp, trees 1m 26s ✗ C Appleman and a Sheet of Paper 2200 data-structures, implementation 1m 22s ✗ D Appleman and Complicated Task 2800 dsu,...

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...

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...

CF 453D - Little Pony and Elements of Harmony

CF 453D - Little Pony and Elements of Harmony Rating: 3000 Tags: dp, matrices Solve time: 2m 30s Verified: yes Solution Problem Understanding We have a vector of energies indexed by all bitmasks of length m . Since n = 2^m , every vertex can be identified with an m -bit number. One transformation step is linear. For every pair of vertices u and v , the contribution from v...

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...

Codeforces Round 272 (Div. 1)

Codeforces Round 272 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 0/2 | Rating range: 2700-3100 | Time: 3m 11s Problem Name Rating Tags Solve Time Verified D Dreamoon and Binary 2700 dp, strings 1m 36s ✗ E Dreamoon and Notepad 3100 data-structures 1m 35s ✗

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...

Codeforces Round 260 (Div. 2)

Codeforces Round 260 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1100-1200 | Time: 2m 34s Problem Name Rating Tags Solve Time Verified A Laptops 1100 sortings 1m 28s ✓ B Fedya and Maths 1200 math, number-theory 1m 6s ✓

CF 465A - inc ARG

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

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: $f_1 = x$ $f_2 = y$ $f_3 = y - x$...

CF 457A - Golden System

CF 457A - Golden System Rating: 1700 Tags: math, meet-in-the-middle Solve time: 1m 15s Verified: yes Solution Problem Understanding In this problem, we are asked to compare two numbers written in an unusual numeral system called the golden system. Each number is represented as a string of 0s and 1s, and the value of a number is computed by interpreting it as a sum of powers of the golden ratio...

CF 470G - Hamming Distance

CF 470G - Hamming Distance Rating: 2300 Tags: *special Solve time: 57s Verified: yes Solution Problem Understanding The task is to compute the Hamming distance between two strings of equal length. In practical terms, you are comparing two sequences of letters and counting how many positions contain different characters. Each mismatch contributes exactly one to the distance. For example, comparing CODECHEF and TOPCODER , every position where the letters differ...

CF 478B - Random Teams

CF 478B - Random Teams Rating: 1300 Tags: combinatorics, constructive algorithms, greedy, math Solve time: 1m 12s Verified: yes Solution Problem Understanding We are given a set of $n$ people who must be partitioned into exactly $m$ non-empty groups. Once the grouping is fixed, every pair of people inside the same group becomes a friendship. A group of size $k$ contributes $\frac{k(k-1)}{2}$ friendships, so the total number of friendships is...

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...

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 ✓

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...

CF 460C - Present

CF 460C - Present Rating: 1700 Tags: binary search, data structures, greedy Solve time: 1m Verified: yes Solution Problem Understanding We are asked to maximize the minimum height of flowers after a limited number of days of watering. Each flower has an initial height, and on any day we can water a contiguous segment of exactly w flowers, increasing each by one. We have m days to apply such waterings,...

CF 464D - World of Darkraft - 2

CF 464D - World of Darkraft - 2 Rating: 2700 Tags: dp, probabilities Solve time: 5m 15s Verified: no Solution

CF 461A - Appleman and Toastman

CF 461A - Appleman and Toastman Rating: 1200 Tags: greedy, sortings Solve time: 2m 14s Verified: yes Solution Problem Understanding We start with a single group containing all given numbers. Whenever Toastman receives a group, he adds the sum of all numbers in that group to the score. If the group contains more than one number, Appleman may split it into two non-empty groups and send both back to Toastman....

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...

Codeforces Round 270

Codeforces Round 270 Type: Special | Problems: 7 | Verified: 5/7 | Rating range: 800-2800 | Time: 12m 18s Problem Name Rating Tags Solve Time Verified A Design Tutorial: Learn from Math 800 math, number-theory 1m 22s ✓ B Design Tutorial: Learn from Life 1300 - 1m 44s ✓ C Design Tutorial: Make It Nondeterministic 1400 greedy 1m 16s ✓ D Design Tutorial: Inverse the Problem 1900 dfs-and-similar, dsu, shortest-paths...

CF 475E - Strongly Connected City 2

CF 475E - Strongly Connected City 2 Rating: 2700 Tags: dfs and similar Solve time: 2m 26s Verified: yes Solution Problem Understanding We start with a connected undirected graph. Every edge must be assigned a direction. After all directions are chosen, some ordered pairs of vertices $(u,v)$ will satisfy that there is a directed path from $u$ to $v$. The goal is not to make the graph strongly connected. The...

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...

CF 468B - Two Sets

CF 468B - Two Sets Rating: 2000 Tags: 2-sat, dfs and similar, dsu, graph matchings, greedy Solve time: 2m 32s Verified: yes Solution Problem Understanding We are given a set of n distinct integers. Every number must be assigned to one of two groups. If a number x is placed into group A , then its complement with respect to a , namely a - x , must also be...

CF 453C - Little Pony and Summer Sun Celebration

CF 453C - Little Pony and Summer Sun Celebration Rating: 2200 Tags: constructive algorithms, dfs and similar, graphs Solve time: 2m 13s Verified: no Solution Problem Understanding We are given an undirected graph and, for every vertex, the parity of how many times that vertex must appear in a walk. A walk is represented by a sequence of vertices. Consecutive vertices in the sequence must be connected by an edge....

CF 478D - Red-Green Towers

CF 478D - Red-Green Towers Rating: 2000 Tags: dp Solve time: 1m 3s Verified: yes Solution Problem Understanding We are asked to build a staircase-like structure made from two types of blocks, red and green. The structure has some number of levels, and the levels form a strict decreasing sequence in size: if the top level has size n , then the next has n-1 , then n-2 , and...

CF 457E - Flow Optimality

CF 457E - Flow Optimality Rating: 3000 Tags: constructive algorithms, flows, math Solve time: 1m 13s Verified: no Solution Problem Understanding We are given a network of nodes connected by links, where each link can carry data in one direction at a time. Each link has a cost proportional to the square of the bandwidth multiplied by a given weight. Some links already have assigned bandwidths, representing the intern’s proposed...

CF 449D - Jzzhu and Numbers

CF 449D - Jzzhu and Numbers Rating: 2400 Tags: bitmasks, combinatorics, dp Solve time: 1m 54s Verified: yes Solution Problem Understanding We are given an array of n non-negative integers. A group is any non-empty subset of array indices. For a chosen group, we take the bitwise AND of all values at those indices. The task is to count how many non-empty groups have bitwise AND equal to 0 ....

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...

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...

CF 474C - Captain Marmot

CF 474C - Captain Marmot Rating: 2000 Tags: brute force, geometry Solve time: 1m 12s Verified: yes Solution Problem Understanding We are asked to help Captain Marmot organize his regiments of moles so that each group of four forms a perfect square on a plane. Each mole starts at a position (xi, yi) and has a “home” at (ai, bi) . The only allowed operation is to rotate a mole...

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...

CF 449C - Jzzhu and Apples

CF 449C - Jzzhu and Apples Rating: 2500 Tags: constructive algorithms, number theory Solve time: 1m 44s Verified: no Solution Problem Understanding We have apples numbered from 1 to n . We want to create as many disjoint pairs as possible such that the two numbers in each pair have greatest common divisor greater than 1 . Each apple can appear in at most one pair. The task is not...

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...

CF 479E - Riding in a Lift

CF 479E - Riding in a Lift Rating: 1900 Tags: combinatorics, dp Solve time: 1m 2s Verified: yes Solution Problem Understanding We are given a line of floors from 1 to n. We start on floor a and we will make exactly k moves. Each move picks a new floor y different from the current floor x, but with a restriction: we are not allowed to move “too far” in...

CF 464B - Restore Cube

CF 464B - Restore Cube Rating: 2000 Tags: brute force, geometry Solve time: 5m 14s Verified: no Solution

CF 455E - Function

CF 455E - Function Rating: 2900 Tags: data structures Solve time: 1m 2s Verified: yes Solution Problem Understanding We are given an array of integers, a[1…n] , and a recursive function f(i, j) defined on it. The function essentially accumulates sums along specific paths: the base case is simply f(1, j) = a[j] , and for later rows, each f(i, j) is the sum of a[j] plus the minimum of...

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....

CF 453E - Little Pony and Lord Tirek

CF 453E - Little Pony and Lord Tirek Rating: 3100 Tags: data structures Solve time: 46s Verified: yes Solution Problem Understanding We have a lineup of ponies, each with three attributes: their current mana, their maximum mana, and their mana regeneration rate per unit time. Over time, Lord Tirek performs several operations called Absorb Mana, each targeting a consecutive segment of ponies. When he absorbs mana at a given time,...

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...

CF 471E - MUH and Lots and Lots of Segments

CF 471E - MUH and Lots and Lots of Segments Rating: 2700 Tags: data structures, dsu Solve time: 2m 1s Verified: no Solution Problem Understanding We start with a collection of axis-aligned segments. Every segment is either horizontal or vertical, and segments of the same orientation never overlap. We are allowed to delete whole segments or only parts of them. After all deletions, the remaining drawing must satisfy three conditions....

CF 455A - Boredom

CF 455A - Boredom Rating: 1500 Tags: dp Solve time: 1m 31s Verified: yes Solution Problem Understanding We are given an array of integers. In one move, we choose a value x that is currently present, earn x points from deleting one occurrence of it, and all occurrences of x - 1 and x + 1 disappear from the array as a consequence. At first glance, the operation looks like...

CF 480D - Parcels

CF 480D - Parcels Rating: 2600 Tags: dp, graphs Solve time: 1m 52s Verified: yes Solution Problem Understanding We are given a collection of parcels, each arriving at a specific time and leaving at another specific time. Each parcel carries a weight, a strength, and a value. We can either ignore a parcel completely or temporarily store it on a special structure that behaves like a stack of boxes. The...

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...

CF 457D - Bingo!

CF 457D - Bingo! Rating: 2700 Tags: combinatorics, math, probabilities Solve time: 1m 42s Verified: yes Solution Problem Understanding We have an $n \times n$ bingo board. Every cell contains a distinct number chosen from $1$ to $m$, and every valid board is equally likely. After the board is generated, exactly $k$ distinct numbers are called. Every set of $k$ numbers is equally likely. A cell becomes marked if its...

CF 460D - Little Victor and Set

CF 460D - Little Victor and Set Rating: 2300 Tags: brute force, constructive algorithms, math Solve time: 1m 21s Verified: no Solution Problem Understanding Victor wants to build a set of integers within a specified range such that the XOR of all its elements is minimized. The set can contain up to k elements, all distinct, and every element must lie between l and r inclusive. The input consists of...

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...

CF 451E - Devu and Flowers

CF 451E - Devu and Flowers Rating: 2300 Tags: bitmasks, combinatorics, number theory Solve time: 1m 37s Verified: yes Solution Problem Understanding We have n flower boxes. From box i , we may take any number of flowers between 0 and f[i] , inclusive. The colors are distinct, so a selection is completely described by how many flowers we take from each box. The task is to count the number...

CF 451D - Count Good Substrings

CF 451D - Count Good Substrings Rating: 2000 Tags: math Solve time: 2m 3s Verified: yes Solution Problem Understanding We are given a binary string consisting only of 'a' and 'b' . For every substring, we repeatedly merge consecutive equal characters into a single character. For example: "aaaa" becomes "a" "aabbaa" becomes "aba" "abbba" becomes "aba" A substring is called good if the compressed string obtained after these merges is...

CF 476E - Dreamoon and Strings

CF 476E - Dreamoon and Strings Rating: 2200 Tags: dp, strings Solve time: 5m 45s Verified: yes Solution Problem Understanding We start with a string s . We may delete exactly x characters, keeping the remaining characters in their original order. The resulting string is a subsequence of s . Inside that resulting string, we look for as many non-overlapping occurrences of a pattern p as possible. For every deletion...

CF 452E - Three strings

CF 452E - Three strings Rating: 2400 Tags: data structures, dsu, string suffix structures, strings Solve time: 2m 7s Verified: yes Solution Problem Understanding We have three strings. For every length $l$ from $1$ up to the length of the shortest string, we must count how many triples of positions $$(i_1,i_2,i_3)$$ produce three equal substrings of length $l$, one taken from each string. Another way to view the task is...

CF 453B - Little Pony and Harmony Chest

CF 453B - Little Pony and Harmony Chest Rating: 2000 Tags: bitmasks, brute force, dp Solve time: 1m 19s Verified: yes Solution Problem Understanding We are given a sequence of integers a1, a2, ..., an with values between 1 and 30, and we need to construct another sequence b1, b2, ..., bn of positive integers such that every pair in b is coprime. The goal is to minimize the sum...

Codeforces Round 259 (Div. 1)

Codeforces Round 259 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1600-3100 | Time: 8m 34s Problem Name Rating Tags Solve Time Verified A Little Pony and Expected Maximum 1600 probabilities 1m 46s ✓ B Little Pony and Harmony Chest 2000 bitmasks, brute-force, dp 1m 19s ✓ C Little Pony and Summer Sun Celebration 2200 constructive-algorithms, dfs-and-similar, graphs 2m 13s ✗ D Little Pony...

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 ,...

CF 455D - Serega and Fun

CF 455D - Serega and Fun Rating: 2700 Tags: data structures Solve time: 1m 27s Verified: yes Solution Problem Understanding We have an array of integers, each between 1 and n , and we need to support two types of operations efficiently. The first operation rotates a segment of the array one step to the right. The second operation counts how many times a particular value occurs in a segment....

CF 457B - Distributed Join

CF 457B - Distributed Join Rating: 1900 Tags: greedy Solve time: 1m 7s Verified: yes Solution Problem Understanding We are asked to minimize the network traffic when joining two distributed tables, A and B, across clusters. Each table is split into several partitions, and each partition contains a certain number of rows. A network operation allows copying a single row from one partition to another. The goal is to ensure...

CF 476C - Dreamoon and Sums

CF 476C - Dreamoon and Sums Rating: 1600 Tags: math Solve time: 1m 19s Verified: yes Solution Problem Understanding We are asked to calculate the sum of all integers $x$ that satisfy a pair of modular conditions with respect to two given integers $a$ and $b$. Specifically, a positive integer $x$ is considered nice if there exists some $k$ between 1 and $a$ such that dividing $x$ by $k$ yields...

Codeforces Round 268 (Div. 1)

Codeforces Round 268 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1500-3100 | Time: 8m 30s Problem Name Rating Tags Solve Time Verified A 24 Game 1500 constructive-algorithms, greedy, math 1m 19s ✓ B Two Sets 2000 2-sat, dfs-and-similar, dsu 2m 32s ✓ C Hack it! 2500 binary-search, constructive-algorithms, math 1m 18s ✓ D Tree 3100 graph-matchings 1m 32s ✗ E Permanent 3100 dp,...

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 ✓...

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...

CF 471D - MUH and Cube Walls

CF 471D - MUH and Cube Walls Rating: 1800 Tags: string suffix structures, strings Solve time: 1m 58s Verified: yes Solution Problem Understanding We have two walls represented by sequences of tower heights. The bears' wall contains n towers, while Horace's wall contains w towers. Horace is allowed to shift his entire wall vertically by any amount. Every tower in his wall must be shifted by the same value, but...

CF 449B - Jzzhu and Cities