Educational Codeforces Round 159 (Rated for Div. 2)

Solutions for Educational Codeforces Round 159 (Rated for Div. 2) (contest 1902). 5/6 problems verified against sample I/O. Difficulty range: 800-2400.

6 items

Educational Codeforces Round 159 (Rated for Div. 2)

Type: Div. 2 | Problems: 6 | Verified: 5/6 | Rating range: 800-2400 | Time: 12m 22s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Binary Imbalance	800	constructive-algorithms	1m 45s	✓
B	Getting Points	1100	binary-search, brute-force, greedy	2m	✓
C	Insert and Equalize	1300	brute-force, constructive-algorithms, greedy	3m 8s	✗
D	Robot Queries	1900	binary-search, data-structures, dp	1m 27s	✓
E	Collapsing Strings	1900	data-structures, strings, trees	1m 40s	✓
F	Trees and XOR Queries Again	2400	data-structures, dfs-and-similar, divide-and-conquer	2m 22s	✓

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CF 1902F - Trees and XOR Queries Again

We are given a tree with n vertices, where each vertex carries an integer value. A tree is an acyclic connected graph, which ensures there is exactly one simple path between any two vertices.

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CF 1902E - Collapsing Strings

We are given a list of $n$ strings, each consisting of lowercase letters. We are asked to compute the sum of lengths of all pairwise “collapsed” concatenations, where the collapse removes consecutive repeated letters at the junction of two strings.

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CF 1902D - Robot Queries

We are given a fixed sequence of moves of a robot on an infinite grid, where each character moves the robot by one unit in one of the four cardinal directions. For every query, we conceptually modify this path by reversing a single contiguous segment of the command string.

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CF 1902C - Insert and Equalize

We are given an array of distinct integers, and our task is twofold: first, we can insert exactly one integer that does not already exist in the array; second, we choose a positive integer $x$ and perform operations where in each operation we add $x$ to a single element.

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CF 1902B - Getting Points

We have a student, Monocarp, who has a sequence of n days in a term. Each day, he can either study or rest. Studying gives him two ways to earn points: attending a lesson (worth l points) and completing practical tasks (worth t points each).

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CF 1902A - Binary Imbalance

We are given a binary string consisting of only '0' and '1' characters. We can perform a specific insertion operation between any two consecutive characters. If the two characters are the same, we insert a '1'. If they are different, we insert a '0'.