Educational Codeforces Round 135 (Rated for Div. 2)

7 problems from Educational Codeforces Round 135 (Rated for Div. 2) (contest 1728), difficulty 800-3100. 6/7 solutions verified against sample I/O.

7 items

Educational Codeforces Round 135 (Rated for Div. 2)

Div. 2 | 7 problems | 6/7 verified | Difficulty 800-3100 | 41m 34s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Colored Balls: Revisited	800	brute-force, greedy, implementation	25,449	6m 15s	✓
B	Best Permutation	800	constructive-algorithms, greedy	20,671	1m 42s	✓
C	Digital Logarithm	1400	data-structures, greedy, sortings	17,878	6m 16s	✓
D	Letter Picking	1800	constructive-algorithms, dp, games	8,242	6m 16s	✓
E	Red-Black Pepper	2300	brute-force, data-structures, greedy	2,030	9m	✓
F	Fishermen	3100	flows, graph-matchings, greedy	506	1m 56s	✓
G	Illumination	2700	binary-search, bitmasks, brute-force	617	10m 9s

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CF 1728G - Illumination

We are working on a one-dimensional segment from 0 to d. Some positions on this line are special points that must be “covered”. We also have a collection of lantern positions, and each lantern can be assigned a nonnegative power up to d.

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CF 1728E - Red-Black Pepper

Each dish must receive exactly one seasoning choice: either red pepper or black pepper. If a dish uses red pepper, it contributes $ai$ to the total tastiness, otherwise it contributes $bi$. So the final score is fully determined once we decide a binary assignment for all dishes.

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CF 1728A - Colored Balls: Revisited

We are given several test cases. In each test case, there are several colors of balls, and each color has a certain number of balls. The total number of balls across all colors is guaranteed to be odd.

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CF 1728C - Digital Logarithm

We are given two arrays of equal length. Each position contains a positive integer, and we are allowed to repeatedly replace a number by the number of digits it has in base 10.

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CF 1728D - Letter Picking

We are playing a two-player game on a string that behaves like a deque. The string initially contains lowercase letters and has even length. Alice moves first, and players alternate.

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CF 1728F - Fishermen

Each fisherman has a fish size ai. We choose an order in which they speak. The first fisherman says his real fish size. Every later fisherman must say the smallest multiple of his own fish size that is strictly larger than the previous announced value.

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CF 1728B - Best Permutation

We need to construct a permutation of the numbers from 1 to n that maximizes the final value of a variable x. The process starts with x = 0. We scan the permutation from left to right.