bitmasks | brain

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

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...

Practice › Codeforces Solutions › Educational Codeforces Round 189 (Rated for Div. 2) ›

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...

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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...

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Codeforces Round 945 (Div. 2)

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

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

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...

Practice › Codeforces Solutions › Codeforces Round 934 (Div. 2) ›

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...

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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 ✗

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

CF 1956D - Nene and the Mex Operator

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

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

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

Practice › Codeforces Solutions ›

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 ✗

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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 ✗

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

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...

Practice › Codeforces Solutions › April Fools Day Contest 2024 ›

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...

Practice › Codeforces Solutions › Codeforces Round 276 (Div. 1) ›

CF 484A - Bits

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

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

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

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

Practice › Codeforces Solutions ›

Codeforces Round 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 ✗

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

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...

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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...

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

CF 1957B - A BIT of a Construction

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

Practice › Codeforces Solutions › Codeforces Round 275 (Div. 1) ›

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...

Practice › Codeforces Solutions › Codeforces Round 941 (Div. 1) ›

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...

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

CF 1946D - Birthday Gift

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

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

CF 1973F - Maximum GCD Sum Queries

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

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

CF 1950G - Shuffling Songs

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

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

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

Practice › Codeforces Solutions ›

Codeforces Round 272 (Div. 2)

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

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

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,...

Practice › Codeforces Solutions ›

Codeforces Round 258 (Div. 2)

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

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

CF 467B - Fedor and New Game

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

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

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...

Practice › Codeforces Solutions › Codeforces Round 270 ›

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...

Practice › Codeforces Solutions ›

Codeforces Round 267 (Div. 2)

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

Practice › Codeforces Solutions › Codeforces Round 257 (Div. 1) ›

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 ....

Practice › Codeforces Solutions › Codeforces Round 259 (Div. 1) ›

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...

Practice › Codeforces Solutions ›

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...

Practice › Codeforces Solutions ›

Codeforces Round 247 (Div. 2)

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

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

CF 333D - Characteristics of Rectangles

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

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

CF 225D - Snake

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

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

CF 241B - Friends

CF 241B - Friends Rating: 2700 Tags: binary search, bitmasks, data structures, math Solve time: 2m 23s Verified: no Solution Problem Understanding We have an array of friend attractiveness values. Every unordered pair of distinct friends produces one possible picture, and the value of that picture is the xor of the two attractiveness values. Among all possible pairs, we want to choose exactly m distinct pairs whose xor values have...

Practice › Codeforces Solutions ›

RCC 2014 Warmup (Div. 2)

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

Practice › Codeforces Solutions ›

Codeforces Round 138 (Div. 2)

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

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

CF 212B - Polycarpus is Looking for Good Substrings

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

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Codeforces Round 235 (Div. 2)

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

Practice › Codeforces Solutions ›

Codeforces Round 127 (Div. 1)

Codeforces Round 127 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1700-2600 | Time: 7m 7s Problem Name Rating Tags Solve Time Verified A Clear Symmetry 1700 constructive-algorithms, dp, math 1m 9s ✓ B Guess That Car! 1800 math, ternary-search 1m ✓ C Fragile Bridges 2000 dp 1m 40s ✓ D Brand New Problem 2600 bitmasks, brute-force, dp 1m 39s ✓ E Thoroughly Bureaucratic...

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

CF 441E - Valera and Number

CF 441E - Valera and Number Rating: 2400 Tags: bitmasks, dp, math, probabilities Solve time: 1m 40s Verified: no Solution Problem Understanding We are asked to model a simple randomized iterative process. We start with a number $x$ and perform $k$ steps. In each step, a random number between 1 and 100 is drawn. With probability $p/100$, the current number is doubled; otherwise, it is incremented by 1. After performing...

Practice › Codeforces Solutions › Codeforces Round 134 (Div. 1) ›

CF 217D - Bitonix' Patrol

CF 217D - Bitonix' Patrol Rating: 2900 Tags: bitmasks, brute force, combinatorics, dfs and similar, math Solve time: 3m 51s Verified: no Solution Problem Understanding The orbit contains n stations placed uniformly on a circle. Adjacent stations are exactly m miles apart, so the whole circumference equals n * m . A patrol is valid if Bitonix starts at some station, uses any subset of the fuel tanks in arbitrary...

Practice › Codeforces Solutions › Codeforces Round 144 (Div. 1) ›

CF 232B - Table

CF 232B - Table Rating: 1900 Tags: bitmasks, combinatorics, dp, math Solve time: 8m 46s Verified: no Solution Problem Understanding We are given a table with n rows and m columns. We can place a single point in any cell, and the goal is to fill the table so that every contiguous square subtable of size n × n contains exactly k points. The output is the total number of...

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Codeforces Round 195 (Div. 2)

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

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

CF 165E - Compatible Numbers

CF 165E - Compatible Numbers Rating: 2200 Tags: bitmasks, brute force, dfs and similar, dp Solve time: 1m 47s Verified: yes Solution Problem Understanding We are given an array of integers, and for every element we must find another array element whose bitwise AND with it is zero. Two numbers are compatible exactly when they do not share any bit set to 1 . For example, if we look at...

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Codeforces Round 144 (Div. 1)

Codeforces Round 144 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 2/4 | Rating range: 1600-2900 | Time: 17m 15s Problem Name Rating Tags Solve Time Verified A Cycles 1600 binary-search, constructive-algorithms, graphs 3m 45s ✓ B Table 1900 bitmasks, combinatorics, dp 8m 46s ✗ C Doe Graphs 2600 constructive-algorithms, divide-and-conquer, dp 2m 23s ✓ D Fence 2900 binary-search, data-structures, string-suffix-structures 2m 21s ✗

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

CF 202A - LLPS

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

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

CF 276D - Little Girl and Maximum XOR

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

Practice › Codeforces Solutions › Coder-Strike 2014 - Round 2 ›

CF 413D - 2048

CF 413D - 2048 Rating: 2000 Tags: bitmasks, dp Solve time: 2m 23s Verified: yes Solution Problem Understanding We process a sequence of tiles, each tile being either 2 or 4 . A tile starts far to the right and slides left. When it touches an equal value, the two merge into a doubled value and the new tile keeps moving. This is the crucial difference from ordinary 2048, merges...

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Codeforces Round 150 (Div. 1)

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

Practice › Codeforces Solutions › Codeforces Round 127 (Div. 1) ›

CF 201D - Brand New Problem

CF 201D - Brand New Problem Rating: 2600 Tags: bitmasks, brute force, dp Solve time: 1m 39s Verified: yes Solution Problem Understanding Lesha has a problem description made of n distinct words, written in a fixed order. Each archive problem is another sequence of words, but archive descriptions may repeat words many times. We want to compare Lesha’s description against every archive description. For one archive problem, we are allowed...

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Croc Champ 2013 - Finals (online version, Div. 1)

Croc Champ 2013 - Finals (online version, Div. 1) Type: Div. 1 | Problems: 4 | Verified: 4/4 | Rating range: 1900-2900 | Time: 12m 12s Problem Name Rating Tags Solve Time Verified A Morning run 2000 binary-search, math, two-pointers 4m 7s ✓ C Memory for Arrays 1900 binary-search, bitmasks, greedy 3m 39s ✓ D Tennis Rackets 2700 brute-force, geometry 1m 52s ✓ E Sheep 2900 binary-search, greedy 2m 34s...

Practice › Codeforces Solutions › Codeforces Round 191 (Div. 2) ›

CF 327E - Axis Walking

CF 327E - Axis Walking Rating: 2300 Tags: bitmasks, combinatorics, constructive algorithms, dp, meet-in-the-middle Solve time: 1m 25s Verified: yes Solution Problem Understanding We are given a multiset of positive segment lengths. Any permutation of these lengths defines a walk along the number line starting from 0, where we cumulatively add each chosen segment. After each segment, we “pause” at the current position, and these pause positions are exactly the...

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

CF 152E - Garden

CF 152E - Garden Rating: 2500 Tags: bitmasks, dp, graphs, trees Solve time: 2m 24s Verified: yes Solution Problem Understanding We have a rectangular grid where every cell has a cost, the number of flowers destroyed if we pave that cell with concrete. Among all cells, there are up to seven special cells containing important buildings. We must choose a connected set of paved cells such that every important cell...

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

CF 251D - Two Sets

CF 251D - Two Sets Rating: 2700 Tags: bitmasks, math Solve time: 1m 13s Verified: yes Solution Problem Understanding We are given a sequence of non-negative integers and must split it into two groups. One group remains with Petya and the other is given to Masha. For each group we compute the XOR of all numbers assigned to it, and we call these values x1 and x2. The objective is...

Practice › Codeforces Solutions › Codeforces Round 150 (Div. 1) ›

CF 243A - The Brand New Function

CF 243A - The Brand New Function Rating: 1600 Tags: bitmasks Solve time: 1m 27s Verified: yes Solution Problem Understanding We are given a sequence of non-negative integers. For any contiguous subarray of this sequence, we can compute its bitwise OR. The problem asks for the number of distinct values obtained from all such subarrays. The input provides the sequence length, $n$, and the sequence itself. The output is a...

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Codeforces Round 150 (Div. 2)

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

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Codeforces Round 206 (Div. 1)

Codeforces Round 206 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 2/5 | Rating range: 1500-2900 | Time: 15m 26s Problem Name Rating Tags Solve Time Verified A Vasya and Robot 1500 brute-force, greedy, math 2m 39s ✓ B Game with Strings 2400 bitmasks, dp, games 2m 1s ✗ C Vasya and Beautiful Arrays 2100 brute-force, dp, number-theory 2m 47s ✓ D Transferring Pyramid 2900 dp 2m 46s...

Practice › Codeforces Solutions › Croc Champ 2013 - Finals (online version, Div. 1) ›

CF 309C - Memory for Arrays

CF 309C - Memory for Arrays Rating: 1900 Tags: binary search, bitmasks, greedy Solve time: 3m 39s Verified: yes Solution Problem Understanding The problem models a simplified memory allocation scenario. We have a computer’s RAM represented as a sequence of cells. Some of these cells are already occupied, and the remaining empty consecutive sequences form memory clusters. Each cluster is described by its size in cells. Separately, a program wants...

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

CF 224B - Array

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

Practice › Codeforces Solutions › Codeforces Round 206 (Div. 1) ›

CF 354B - Game with Strings

CF 354B - Game with Strings Rating: 2400 Tags: bitmasks, dp, games Solve time: 2m 1s Verified: no Solution Problem Understanding We are given an $n \times n$ grid of lowercase letters. A valid string is formed by walking from the top-left cell to any reachable cell by moving only right or down, always starting at $(1,1)$. Every move appends the character of the new cell, so each valid string...

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Codeforces Round 139 (Div. 2)

Codeforces Round 139 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 3/4 | Rating range: 1600-2200 | Time: 9m 47s Problem Name Rating Tags Solve Time Verified B Well-known Numbers 1600 binary-search, greedy, number-theory 3m 27s ✗ C Barcode 1700 dp, matrices 1m 54s ✓ D Snake 2200 bitmasks, dfs-and-similar, graphs 58s ✓ E Unsolvable 2100 math, number-theory 3m 28s ✓

Practice › Codeforces Solutions › Codeforces Round 150 (Div. 2) ›

CF 244B - Undoubtedly Lucky Numbers

CF 244B - Undoubtedly Lucky Numbers Rating: 1600 Tags: bitmasks, brute force, dfs and similar Solve time: 1m 8s Verified: yes Solution Problem Understanding We are given a single positive integer $n$, and we need to count how many integers from 1 up to $n$ have a very specific property: there exists a pair of digits $x$ and $y$ such that every digit in the number’s decimal representation is either...

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Codeforces Round 169 (Div. 2)

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

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Codeforces Round 245 (Div. 1)

Codeforces Round 245 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1300-3000 | Time: 6m 47s Problem Name Rating Tags Solve Time Verified A Xor-tree 1300 dfs-and-similar, trees 1m 38s ✓ B Working out 1600 dp 57s ✓ C Guess the Tree 2300 bitmasks, constructive-algorithms, dp 1m 26s ✓ D Tricky Function 2200 data-structures, divide-and-conquer, geometry 1m 9s ✓ E Points and Segments 3000...

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Codeforces Round 194 (Div. 1)

Codeforces Round 194 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 1/2 | Rating range: 1600-2100 | Time: 3m 54s Problem Name Rating Tags Solve Time Verified A Secrets 1600 greedy 1m 42s ✓ D Characteristics of Rectangles 2100 binary-search, bitmasks, brute-force 2m 12s ✗

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

CF 431D - Random Task

CF 431D - Random Task Rating: 2100 Tags: binary search, bitmasks, combinatorics, dp, math Solve time: 2m 1s Verified: yes Solution Problem Understanding We need to find a positive integer n such that inside the interval (n, 2n] , exactly m numbers have exactly k ones in their binary representation. Another way to phrase the condition is this: If f(x) denotes the number of integers in [0, x] whose binary...

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

CF 417D - Cunning Gena

CF 417D - Cunning Gena Rating: 1900 Tags: bitmasks, dp, greedy, sortings Solve time: 34s Verified: no Solution Problem Understanding Gena has a set of problems, and a group of friends who can each solve some subset of them. If Gena hires a friend, that friend will solve all problems they are capable of solving, covering multiple problems at once. Each friend has two independent costs: a fixed monetary payment...

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

CF 401D - Roman and Numbers

CF 401D - Roman and Numbers Rating: 2000 Tags: bitmasks, brute force, combinatorics, dp, number theory Solve time: 1m 19s Verified: yes Solution Problem Understanding We are asked to count the number of integers that can be formed by permuting the digits of a given number $n$, do not start with zero, and are divisible by a given modulus $m$. The input $n$ can be as large as $10^{18}$, which...

Practice › Codeforces Solutions ›

Codeforces Round 108 (Div. 2)

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

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Codeforces Round 127 (Div. 2)

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

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

CF 242E - XOR on Segment

CF 242E - XOR on Segment Rating: 2000 Tags: bitmasks, data structures Solve time: 3m 32s Verified: yes Solution Problem Understanding We are maintaining a mutable array of integers where two types of operations are performed repeatedly: range sum queries and range updates where every element in a subarray is XORed with a fixed value. The task is to output the sum after each query of the first type, while...

Practice › Codeforces Solutions › Codeforces Round 195 (Div. 2) ›

CF 336E - Vasily the Bear and Painting Square

CF 336E - Vasily the Bear and Painting Square Rating: 2700 Tags: bitmasks, combinatorics, dp, implementation Solve time: 3m 22s Verified: yes Solution Problem Understanding Vasily the Bear is creating a geometric structure on the plane using a sequence of squares and line segments, all centered at the origin. The parameter n controls the number of nested squares he draws, each forming vertices at multiples of 2_i_ and 2_i_+1 along...

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Coder-Strike 2014 - Round 2

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

Practice › Codeforces Solutions › Codeforces Round 245 (Div. 1) ›

CF 429C - Guess the Tree

CF 429C - Guess the Tree Rating: 2300 Tags: bitmasks, constructive algorithms, dp, greedy, trees Solve time: 1m 26s Verified: yes Solution Problem Understanding The problem asks us to reconstruct a rooted tree given constraints on the sizes of the subtrees for each node. You are given an array c of length n , where c[i] represents the total number of nodes in the subtree rooted at node i ....

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VK Cup 2012 Finals (unofficial online-version)

VK Cup 2012 Finals (unofficial online-version) Type: Special | Problems: 5 | Verified: 1/5 | Rating range: 1500-3000 | Time: 9m 48s Problem Name Rating Tags Solve Time Verified A Privatization 3000 flows, graphs 2m 20s ✗ B Polycarpus is Looking for Good Substrings 2300 bitmasks, hashing, implementation 1m 54s ✓ C Cowboys 2100 combinatorics, dp, math 1m 28s ✗ D Cutting a Fence 2500 binary-search, data-structures, dsu 1m 8s...

Practice › Codeforces Solutions ›

Codeforces Beta Round 86 (Div. 2 Only)

Codeforces Beta Round 86 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1500 | Time: 4m 17s Problem Name Rating Tags Solve Time Verified A Cifera 1000 math 1m 58s ✓ B PFAST Inc. 1500 bitmasks, brute-force, graphs 2m 19s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 83 (Div. 1 Only) ›

CF 107C - Arrangement

CF 107C - Arrangement Rating: 2400 Tags: bitmasks, dp Solve time: 2m 35s Verified: yes Solution Problem Understanding We have n seats and n professors. Professor 1 is the most senior, professor n is the least senior. Some pairs of seats impose ordering constraints. If (a, b) is given, then the professor sitting in seat a must be more senior than the professor sitting in seat b . A seating...

Practice › Codeforces Solutions › Codeforces Beta Round 72 (Div. 1 Only) ›

CF 83E - Two Subsequences

CF 83E - Two Subsequences Rating: 2800 Tags: bitmasks, dp Solve time: 1m 43s Verified: yes Solution Problem Understanding We are given a sequence of binary strings, all of equal length, and we need to split them into two subsequences in a way that minimizes the sum of the lengths of their compressed forms. The compression function f works incrementally: when combining two strings, it produces the shortest string that...

Practice › Codeforces Solutions › Codeforces Beta Round 71 ›

CF 79D - Password

CF 79D - Password Rating: 2800 Tags: bitmasks, dp, shortest paths Solve time: 2m 11s Verified: yes Solution Problem Understanding We start with a row of n panels, all turned OFF. The target password is another configuration where exactly k specific positions must be ON and every other position must remain OFF. One operation chooses a segment of consecutive panels whose length belongs to the array a . Every panel...

Practice › Codeforces Solutions › Codeforces Beta Round 65 (Div. 2) ›

CF 71E - Nuclear Fusion

CF 71E - Nuclear Fusion Rating: 2200 Tags: bitmasks, dp Solve time: 1m 50s Verified: no Solution Problem Understanding We are given a set of atoms with known atomic numbers and a target set of atoms we want to produce using fusion. Each fusion operation combines exactly two atoms into one, and the resulting atom’s atomic number is the sum of the two original numbers. We cannot split atoms. Every...

Practice › Codeforces Solutions ›

Codeforces Beta Round 8

Codeforces Beta Round 8 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1200-2600 | Time: 6m 59s Problem Name Rating Tags Solve Time Verified A Train and Peter 1200 strings 1m 17s ✓ B Obsession with Robots 1400 constructive-algorithms, graphs, implementation 56s ✓ C Looking for Order 2000 bitmasks, dp 1m 48s ✓ D Two Friends 2600 binary-search, geometry 1m 54s ✓ E Beads 2600 dp, graphs...

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Codeforces Beta Round 27 (Codeforces format, Div. 2)

Codeforces Beta Round 27 (Codeforces format, Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1200-2200 | Time: 6m 38s Problem Name Rating Tags Solve Time Verified A Next Test 1200 implementation, sortings 1m 13s ✓ B Tournament 1300 bitmasks, brute-force, dfs-and-similar 1m 3s ✓ C Unordered Subsequence 1900 constructive-algorithms, greedy 1m 18s ✗ D Ring Road 2 2200 2-sat, dfs-and-similar, dsu 1m 30s ✓...

Practice › Codeforces Solutions › Codeforces Beta Round 8 ›

CF 8C - Looking for Order

CF 8C - Looking for Order Rating: 2000 Tags: bitmasks, dp Solve time: 1m 48s Verified: yes Solution Problem Understanding We have a fixed starting point, the handbag, and up to 24 scattered objects on a 2D plane. Lena always starts at the handbag, walks around collecting at most two objects, returns to the handbag, then repeats until every object is stored back. The travel cost between two positions is...

Practice › Codeforces Solutions › Codeforces Alpha Round 21 (Codeforces format) ›

CF 21D - Traveling Graph

CF 21D - Traveling Graph Rating: 2400 Tags: bitmasks, graph matchings, graphs Solve time: 42s Verified: yes Solution Problem Understanding We are given a weighted undirected graph with up to 15 vertices and up to 2000 edges. Each edge has a positive weight, and there may be multiple edges connecting the same pair of vertices or edges that loop back to the same vertex. The task is to find the...

Practice › Codeforces Solutions › Codeforces Beta Round 16 (Div. 2 Only) ›

CF 16E - Fish

CF 16E - Fish Rating: 1900 Tags: bitmasks, dp, probabilities Solve time: 1m 34s Verified: yes Solution Problem Understanding We have n fish in a lake. Every day, exactly one unordered pair of currently alive fish is chosen uniformly at random. When fish i meets fish j , fish i eats fish j with probability a[i][j] , and fish j eats fish i with probability a[j][i] = 1 - a[i][j]...

Practice › Codeforces Solutions › Codeforces Beta Round 11 ›

CF 11D - A Simple Task

CF 11D - A Simple Task Rating: 2200 Tags: bitmasks, dp, graphs Solve time: 1m 29s Verified: yes Solution Problem Understanding We are asked to count the number of simple cycles in an undirected graph. A simple cycle is a closed loop where no vertex or edge is repeated. The input gives us the number of vertices n and the number of edges m , followed by m pairs of...

Practice › Codeforces Solutions › Codeforces Beta Round 85 (Div. 1 Only) ›

CF 111C - Petya and Spiders

CF 111C - Petya and Spiders Rating: 2100 Tags: bitmasks, dp, dsu Solve time: 2m 34s Verified: yes Solution Problem Understanding We are given a board of size n by m , with a spider on every cell. Each spider can move to any adjacent cell or stay in place, as long as it stays inside the board. All spiders move simultaneously, and multiple spiders can occupy the same cell...

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Codeforces Beta Round 11

Codeforces Beta Round 11 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 900-2800 | Time: 8m 46s Problem Name Rating Tags Solve Time Verified A Increasing Sequence 900 constructive-algorithms, implementation, math 1m 24s ✓ B Jumping Jack 1600 math 1m 26s ✓ C How Many Squares? 2200 implementation 2m 42s ✓ D A Simple Task 2200 bitmasks, dp, graphs 1m 29s ✓ E Forward, march! 2800 binary-search,...

Practice › Codeforces Solutions › Yandex.Algorithm 2011: Finals ›

CF 97D - Robot in Basement

CF 97D - Robot in Basement Rating: 2700 Tags: bitmasks, brute force, implementation Solve time: 2m 39s Verified: yes Solution Problem Understanding We have a grid representing a basement. Some cells are walls, some are walkable, and exactly one walkable cell is the exit. A robot starts in an unknown walkable cell. We are given a fixed sequence of movement commands such as L , R , U , D...

Practice › Codeforces Solutions › Codeforces Beta Round 77 (Div. 2 Only) ›

CF 96B - Lucky Numbers (easy)

CF 96B - Lucky Numbers (easy) Rating: 1300 Tags: binary search, bitmasks, brute force Solve time: 4m 51s Verified: yes Solution Problem Understanding We need to find the smallest number greater than or equal to a given integer such that: Every digit is either 4 or 7 . The count of 4 s equals the count of 7 s. These numbers are called super lucky numbers. For example, 47 is...

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Codeforces Beta Round 85 (Div. 1 Only)

Codeforces Beta Round 85 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1400-2900 | Time: 12m 59s Problem Name Rating Tags Solve Time Verified A Petya and Inequiations 1400 greedy 2m 33s ✗ B Petya and Divisors 1900 binary-search, data-structures, number-theory 2m 50s ✓ C Petya and Spiders 2100 bitmasks, dp, dsu 2m 34s ✓ D Petya and Coloring 2300 combinatorics, dp 2m...

Practice › Codeforces Solutions › Codeforces Beta Round 49 (Div. 2) ›

CF 53E - Dead Ends

CF 53E - Dead Ends Rating: 2500 Tags: bitmasks, dp Solve time: 3m 58s Verified: no Solution Problem Understanding We are given an undirected connected graph representing roads between junctions. The mayor wants to remove some roads so that the remaining graph becomes a tree, meaning it stays connected and contains exactly n - 1 edges. Among all such spanning trees, we only care about the ones that contain exactly...

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Codeforces Beta Round 49 (Div. 2)

Codeforces Beta Round 49 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1100-2500 | Time: 13m 28s Problem Name Rating Tags Solve Time Verified A Autocomplete 1100 implementation 3m 28s ✓ B Blog Photo 1700 binary-search, implementation 2m 21s ✓ C Little Frog 1200 constructive-algorithms 1m 35s ✓ D Physical Education 1500 sortings 2m 6s ✓ E Dead Ends 2500 bitmasks, dp 3m 58s...

Practice › Codeforces Solutions › Codeforces Beta Round 27 (Codeforces format, Div. 2) ›

CF 27B - Tournament

CF 27B - Tournament Rating: 1300 Tags: bitmasks, brute force, dfs and similar, greedy Solve time: 1m 3s Verified: yes Solution Problem Understanding We are asked to reconstruct the missing result of a round-robin tournament. There are n participants, and every participant plays against every other participant exactly once. Each match has a clear winner and a loser, and no two participants have the same intrinsic ability: a lower "sleep...

Practice › Codeforces Solutions › Codeforces Beta Round 86 (Div. 2 Only) ›

CF 114B - PFAST Inc.

CF 114B - PFAST Inc. Rating: 1500 Tags: bitmasks, brute force, graphs Solve time: 2m 19s Verified: yes Solution Problem Understanding We are given a small group of people and a list of pairs who cannot work together. We need to choose the largest possible subset such that every pair inside the chosen group is compatible. This is naturally a graph problem. Think of each volunteer as a vertex. If...

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Codeforces Beta Round 59 (Div. 2)

Codeforces Beta Round 59 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 900-2000 | Time: 8m 47s Problem Name Rating Tags Solve Time Verified A Sinking Ship 900 implementation, sortings, strings 1m 31s ✓ B Settlers' Training 1200 implementation 1m 35s ✓ C Bulls and Cows 1700 brute-force, implementation 1m 48s ✓ D Dividing Island 1900 constructive-algorithms 1m 40s ✗ E Sweets Game 2000...

Practice › Codeforces Solutions › All-Ukrainian School Olympiad in Informatics ›

CF 76C - Mutation

CF 76C - Mutation Rating: 2700 Tags: bitmasks, dp, math Solve time: 2m 6s Verified: yes Solution Problem Understanding We are given a string representing the genome of an organism, where each character is one of the first K capital letters. Adjacent genes contribute to the total “risk of disease” according to a given K × K matrix of non-negative integers. Additionally, we are allowed to remove all occurrences of...

Practice › Codeforces Solutions › Codeforces Beta Round 59 (Div. 2) ›

CF 63E - Sweets Game

CF 63E - Sweets Game Rating: 2000 Tags: bitmasks, dfs and similar, dp, games, implementation Solve time: 2m 13s Verified: yes Solution Problem Understanding The board is a fixed hexagon with 19 cells. Some cells contain chocolates, some are empty. Two players alternate moves, and a move consists of choosing a contiguous segment of chocolates that lies on a straight line parallel to one of the three hexagon directions. Every...

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Codeforces Beta Round 77 (Div. 2 Only)

Codeforces Beta Round 77 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 900-1300 | Time: 6m 15s Problem Name Rating Tags Solve Time Verified A Football 900 implementation, strings 1m 24s ✓ B Lucky Numbers (easy) 1300 binary-search, bitmasks, brute-force 4m 51s ✓

#bitmasks

CF 2222E - Seek the Truth

CF 2225D - Exceptional Segments

Educational Codeforces Round 189 (Rated for Div. 2)

Codeforces Round 945 (Div. 2)

CF 1948G - MST with Matching

CF 1944B - Equal XOR

Codeforces Round 934 (Div. 2)

CF 1956D - Nene and the Mex Operator

CF 1975F - Set

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

Codeforces Round 275 (Div. 1)

CF 1967C - Fenwick Tree

CF 1952I - Dark Matter

CF 484A - Bits

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

Codeforces Round 276 (Div. 1)

CF 1955H - The Most Reckless Defense

Codeforces Round 941 (Div. 1)

CF 1957B - A BIT of a Construction

CF 482C - Game with Strings

CF 1965B - Missing Subsequence Sum

CF 1946D - Birthday Gift

CF 1973F - Maximum GCD Sum Queries

CF 1950G - Shuffling Songs

CF 1973B - Cat, Fox and the Lonely Array

Codeforces Round 272 (Div. 2)

CF 476B - Dreamoon and WiFi

Codeforces Round 258 (Div. 2)

CF 467B - Fedor and New Game

CF 451E - Devu and Flowers

CF 472G - Design Tutorial: Increase the Constraints

Codeforces Round 267 (Div. 2)

CF 449D - Jzzhu and Numbers

CF 453B - Little Pony and Harmony Chest

Codeforces Round 259 (Div. 1)

Codeforces Round 247 (Div. 2)

CF 333D - Characteristics of Rectangles

CF 225D - Snake

CF 241B - Friends

RCC 2014 Warmup (Div. 2)

Codeforces Round 138 (Div. 2)

CF 212B - Polycarpus is Looking for Good Substrings

Codeforces Round 235 (Div. 2)

Codeforces Round 127 (Div. 1)

CF 441E - Valera and Number

CF 217D - Bitonix' Patrol

CF 232B - Table

Codeforces Round 195 (Div. 2)

CF 165E - Compatible Numbers

Codeforces Round 144 (Div. 1)

CF 202A - LLPS

CF 276D - Little Girl and Maximum XOR

CF 413D - 2048

Codeforces Round 150 (Div. 1)

CF 201D - Brand New Problem

Croc Champ 2013 - Finals (online version, Div. 1)

CF 327E - Axis Walking

CF 152E - Garden

CF 251D - Two Sets

CF 243A - The Brand New Function

Codeforces Round 150 (Div. 2)

Codeforces Round 206 (Div. 1)

CF 309C - Memory for Arrays

CF 224B - Array

CF 354B - Game with Strings

Codeforces Round 139 (Div. 2)

CF 244B - Undoubtedly Lucky Numbers

Codeforces Round 169 (Div. 2)

Codeforces Round 245 (Div. 1)

Codeforces Round 194 (Div. 1)

CF 431D - Random Task

CF 417D - Cunning Gena

CF 401D - Roman and Numbers

Codeforces Round 108 (Div. 2)

Codeforces Round 127 (Div. 2)

CF 242E - XOR on Segment

CF 336E - Vasily the Bear and Painting Square

Coder-Strike 2014 - Round 2

CF 429C - Guess the Tree