Educational Codeforces Round 75 (Rated for Div. 2)

7 problems from Educational Codeforces Round 75 (Rated for Div. 2) (contest 1251), difficulty 1000-2500. 1/7 solutions verified against sample I/O.

7 items

Educational Codeforces Round 75 (Rated for Div. 2)

Div. 2 | 7 problems | 1/7 verified | Difficulty 1000-2500 | 28m

#	Problem	Rating	Tags	Accepted	Time	✓
A	Broken Keyboard	1000	brute-force, strings, two-pointers	21,550	5m 7s
B	Binary Palindromes	1400	greedy, strings	11,617	2m 36s
C	Minimize The Integer	1600	greedy, two-pointers	14,331	2m 40s
D	Salary Changing	1900	binary-search, greedy, sortings	6,465	4m 31s	✓
E1	Voting (Easy Version)	2300	data-structures, dp, greedy	2,587	4m 12s
E2	Voting (Hard Version)	2400	binary-search, data-structures, greedy	2,951	4m 8s
F	Red-White Fence	2500	combinatorics, fft	978	4m 46s

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CF 1251F - Red-White Fence

We are given a multiset of white boards, each with a fixed integer length, and a very small set of red boards. From these boards we want to form a “mountain shaped” fence. The fence uses exactly one red board, which must be the unique maximum element in the sequence.

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CF 1251E2 - Voting (Hard Version)

Each voter comes with two independent ways to make them support you. You may directly pay a fixed cost to activate any voter.

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CF 1251D - Salary Changing

We are given several independent scenarios. In each scenario, there are an odd number of employees, and each employee has a salary interval from which their final salary must be chosen.

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CF 1251E1 - Voting (Easy Version)

We are given a set of voters, and each voter can be activated in one of two ways. Either we directly pay a fixed cost to convince them, or we can exploit a dependency: if enough other voters are already convinced, they will join for free.

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CF 1251A - Broken Keyboard

We are given a final string that appeared on a screen after someone pressed keyboard keys one by one. Each key corresponds to a lowercase Latin letter, and each key is either always healthy or always broken during the entire typing process.

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CF 1251C - Minimize The Integer

We are given a very long decimal string, but the digits are not free to move arbitrarily. The only allowed move is swapping two neighboring digits, and even that swap is restricted: the two digits must have different parity, meaning one is even and the other is odd.

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CF 1251B - Binary Palindromes

We are given several binary strings and allowed to repeatedly swap characters between any two positions in any strings.