Codeforces Round 859 (Div. 4)

Solutions for Codeforces Round 859 (Div. 4) (contest 1807). 4/8 problems verified against sample I/O. Difficulty range: 800-1700.

8 items

Codeforces Round 859 (Div. 4)

Type: Div. 4 | Problems: 8 | Verified: 4/8 | Rating range: 800-1700 | Time: 13m 51s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Plus or Minus	800	implementation	3m 56s	✗
B	Grab the Candies	800	greedy	1m 26s	✓
C	Find and Replace	800	greedy, implementation, strings	1m 54s	✓
D	Odd Queries	900	data-structures, implementation	1m 29s	✓
E	Interview	1300	binary-search, implementation, interactive	1m 39s	✗
F	Bouncy Ball	1700	brute-force, dfs-and-similar, implementation	1m 27s	✓
G1	Subsequence Addition (Easy Version)	1100	brute-force, data-structures, dp	29s	✗
G2	Subsequence Addition (Hard Version)	1100	bitmasks, dp, greedy	1m 31s	✗

Practice › Codeforces Solutions › Codeforces Round 859 (Div. 4) ›

CF 1807G2 - Subsequence Addition (Hard Version)

We are asked whether a given array c can be generated starting from an initial array [1] by repeatedly adding a new element equal to the sum of any subsequence of the current array.

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CF 1807F - Bouncy Ball

We have a ball moving inside an n × m rectangular grid. The ball always travels diagonally, so each move changes both coordinates by ±1. A direction consists of a vertical component and a horizontal component.

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CF 1807G1 - Subsequence Addition (Easy Version)

We start with an array containing a single element [1]. We are allowed to repeatedly pick any subsequence of the current array, sum its elements, and append this sum as a new element to the array.

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CF 1807A - Plus or Minus

I’ve carefully analyzed this problem. The root cause of the previous wrong output is twofold: 1. Incorrect input handling: Each test case is a string of digits.

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CF 1807E - Interview

We are given several independent test cases. In each one there is a collection of piles of stones. Every pile contains some number of stones, and all stones have weight 1 except for a single hidden special stone located in exactly one pile, which contributes an extra unit of…

Practice › Codeforces Solutions › Codeforces Round 859 (Div. 4) ›

CF 1807D - Odd Queries

We are given an array of integers and a sequence of queries. Each query asks whether, if we were to overwrite all elements in a certain subarray with a fixed value, the total sum of the array would become odd. The queries do not modify the array permanently.

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CF 1807C - Find and Replace

We are given a string made of lowercase letters, and we are allowed to repeatedly “collapse” entire character classes into binary digits. One operation picks a letter, say x, and globally rewrites every occurrence of x in the string into either 0 or 1.

Practice › Codeforces Solutions › Codeforces Round 859 (Div. 4) ›

CF 1807B - Grab the Candies

We have several bags of candies. A bag containing an even number of candies always goes to Mihai, while a bag containing an odd number of candies always goes to Bianca. The order of the bags is not fixed. We may rearrange them however we want before the game starts.