Educational Codeforces Round 177 (Rated for Div. 2)

6 problems from Educational Codeforces Round 177 (Rated for Div. 2) (contest 2086), difficulty 800-3000. 4/6 solutions verified against sample I/O.

6 items

Educational Codeforces Round 177 (Rated for Div. 2)

Div. 2 | 6 problems | 4/6 verified | Difficulty 800-3000 | 9m 38s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Cloudberry Jam	800	math	33,538	1m 10s	✓
B	Large Array and Segments	1100	binary-search, brute-force, greedy	18,987	1m 23s	✓
C	Disappearing Permutation	1300	dfs-and-similar, dp, dsu	16,121	1m 57s
D	Even String	1700	brute-force, combinatorics, dp	8,360	1m 35s	✓
E	Zebra-like Numbers	2400	bitmasks, brute-force, constructive-algorithms	1,664	2m 8s	✓
F	Online Palindrome	3000	brute-force, constructive-algorithms, interactive	142	1m 25s

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CF 2086E - Zebra-like Numbers

A zebra-like number is a positive integer whose binary representation looks like 1, 101, 10101, 1010101, ... In other words, the bits alternate and the least significant bit is 1. Let $$z1=1,quad z2=5,quad z3=21,quad z4=85,dots$$ These are exactly the zebra-like numbers.

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CF 2086F - Online Palindrome

We are interacting with a process that reveals a binary string one character at a time. After each reveal, we append the new character to a working string, and we are allowed to freely swap any two positions in this working string.

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CF 2086D - Even String

We are asked to count how many strings can be built from given letter counts such that equal letters always occupy positions of the same parity.

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CF 2086C - Disappearing Permutation

We are given a permutation of integers from 1 to n, which means every number in that range appears exactly once in an array of size n. We then perform a sequence of queries, where in each query we replace a specific element of the array with zero.

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CF 2086B - Large Array and Segments

We are given an array a of length n and a positive integer k. From a, we construct a larger array b by repeating a exactly k times. That is, b has length n k, and its first n elements are the same as a, and the remaining elements repeat a in order.

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CF 2086A - Cloudberry Jam

We are asked to determine how many kilograms of cloudberries are needed to produce a certain number of jars of jam, given that the jam is made by combining equal amounts of berries and sugar, and that during cooking, 25% of the total mass evaporates.