Codeforces Round 780 (Div. 3)

Solutions for Codeforces Round 780 (Div. 3) (contest 1660). 3/7 problems verified against sample I/O. Difficulty range: 800-2100.

7 items

Codeforces Round 780 (Div. 3)

Type: Div. 3 | Problems: 7 | Verified: 3/7 | Rating range: 800-2100 | Time: 22m 35s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Vasya and Coins	800	greedy, math	5m 9s	✓
B	Vlad and Candies	800	math	8m 12s	✗
C	Get an Even String	1300	dp, greedy, strings	1m 50s	✗
D	Maximum Product Strikes Back	1600	brute-force, implementation, math	2m 14s	✗
E	Matrix and Shifts	1600	brute-force, constructive-algorithms, greedy	1m 18s	✓
F1	Promising String (easy version)	1700	brute-force, implementation, math	1m 50s	✓
F2	Promising String (hard version)	2100	data-structures, implementation, math	2m 2s	✗

Practice › Codeforces Solutions › Codeforces Round 780 (Div. 3) ›

CF 1660B - Vlad and Candies

Thank you for the clarification. Now we can carefully analyze the problem. The input/output mismatch shows that the previous solution produces RRRWW for the first test case, while the expected output is RWRRW.

Practice › Codeforces Solutions › Codeforces Round 780 (Div. 3) ›

CF 1660F2 - Promising String (hard version)

We are given a string consisting only of plus and minus signs. A substring of this string is considered promising if, through repeated replacement of two consecutive minuses with a single plus, the substring can be transformed into a balanced string, meaning it has an equal…

Practice › Codeforces Solutions › Codeforces Round 780 (Div. 3) ›

CF 1660F1 - Promising String (easy version)

We are given a string consisting of '+' and '-'. For every non-empty substring, we must determine whether it is promising.

Practice › Codeforces Solutions › Codeforces Round 780 (Div. 3) ›

CF 1660E - Matrix and Shifts

We are given a binary square matrix, and we are allowed to rearrange it using cyclic shifts of rows and columns. These shifts do not change values, they only rotate positions, so what ultimately matters is how we align the matrix before we start paying to flip bits.

Practice › Codeforces Solutions › Codeforces Round 780 (Div. 3) ›

CF 1660A - Vasya and Coins

Vasya has two types of coins in his wallet: 1-burle coins and 2-burle coins. The problem asks for the smallest positive integer amount of money that he cannot pay exactly using the coins in his possession.

Practice › Codeforces Solutions › Codeforces Round 780 (Div. 3) ›

CF 1660D - Maximum Product Strikes Back

We are given an array of integers where each value is extremely small in magnitude, only from -2 to 2. From this array, we are allowed to delete a prefix and a suffix, leaving a contiguous middle segment. That remaining segment could even be empty.

Practice › Codeforces Solutions › Codeforces Round 780 (Div. 3) ›

CF 1660C - Get an Even String

We are given a string and we are allowed to delete characters anywhere, not necessarily in a continuous segment. After deletions, we want the remaining characters to form a very rigid structure: the string must be split into consecutive pairs, and each pair must consist of two…