Educational Codeforces Round 121 (Rated for Div. 2)

Solutions for Educational Codeforces Round 121 (Rated for Div. 2) (contest 1626). 1/6 problems verified against sample I/O. Difficulty range: 800-2800.

6 items

Educational Codeforces Round 121 (Rated for Div. 2)

Type: Div. 2 | Problems: 6 | Verified: 1/6 | Rating range: 800-2800 | Time: 13m 22s

Problem Name Rating Tags Solve Time Verified
A Equidistant Letters 800 constructive-algorithms, sortings 1m 58s ✗
B Minor Reduction 1100 greedy, strings 1m 12s ✓
C Monsters And Spells 1700 binary-search, data-structures, dp 5m 17s ✗
D Martial Arts Tournament 2100 binary-search, brute-force, greedy 1m 35s ✗
E Black and White Tree 2400 dfs-and-similar, greedy, trees 1m 43s ✗
F A Random Code Problem 2800 combinatorics, dp, math 1m 37s ✗
Practice › Codeforces Solutions › Educational Codeforces Round 121 (Rated for Div. 2) ›

CF 1626C - Monsters And Spells

- First line: t - number of test cases - For each test case: - First line: n - size of the grid (n x n) - Next n lines: n integers per line - the neighbor XOR sums There is no m in the problem, only n. The earlier input with 8 4 seems like an incorrect test input format.
codeforces competitive-programming binary-search data-structures dp greedy implementation math two-pointers Jun 10, 2026
Practice › Codeforces Solutions › Educational Codeforces Round 121 (Rated for Div. 2) ›

CF 1626F - A Random Code Problem

We are working with a long array generated by a linear recurrence, and then a randomized process that repeatedly samples elements from this array and mutates the sampled value. At each of $k$ rounds, we pick a uniformly random index $idx$ from $0$ to $n-1$.
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Practice › Codeforces Solutions › Educational Codeforces Round 121 (Rated for Div. 2) ›

CF 1626E - Black and White Tree

We are given a tree with $n$ vertices, where each vertex is either black or white. A "chip" can be placed on any vertex, and in each operation, you pick a black vertex $y$ different from the last chosen black vertex and move the chip one step along the shortest path from its…
codeforces competitive-programming dfs-and-similar greedy trees Jun 10, 2026
Practice › Codeforces Solutions › Educational Codeforces Round 121 (Rated for Div. 2) ›

CF 1626D - Martial Arts Tournament

We are given a multiset of weights, and we must split these values into three groups using two cut points on the number line.
codeforces competitive-programming binary-search brute-force greedy math Jun 10, 2026
Practice › Codeforces Solutions › Educational Codeforces Round 121 (Rated for Div. 2) ›

CF 1626A - Equidistant Letters

We are given a short string where each character appears either once or twice. The task is to permute the characters so that whenever a letter appears twice, the gap between its two occurrences is identical for all such letters.
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Practice › Codeforces Solutions › Educational Codeforces Round 121 (Rated for Div. 2) ›

CF 1626B - Minor Reduction

We are given a large integer, represented as a string of digits without leading zeros, and we are allowed to perform exactly one operation: pick two consecutive digits and replace them with their sum.
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