Educational Codeforces Round 155 (Rated for Div. 2)

Solutions for Educational Codeforces Round 155 (Rated for Div. 2) (contest 1879). 4/6 problems verified against sample I/O. Difficulty range: 800-2800.

6 items

Educational Codeforces Round 155 (Rated for Div. 2)

Type: Div. 2 | Problems: 6 | Verified: 4/6 | Rating range: 800-2800 | Time: 15m 6s

Problem Name Rating Tags Solve Time Verified
A Rigged! 800 greedy 5m 30s ✓
B Chips on the Board 900 constructive-algorithms, greedy 1m 36s ✓
C Make it Alternating 1300 combinatorics, dp, greedy 1m 54s ✗
D Sum of XOR Functions 1700 bitmasks, combinatorics, divide-and-conquer 2m 23s ✓
E Interactive Game with Coloring 2400 brute-force, constructive-algorithms, dfs-and-similar 1m 59s ✓
F Last Man Standing 2800 brute-force, data-structures, number-theory 1m 44s ✗
Practice › Codeforces Solutions › Educational Codeforces Round 155 (Rated for Div. 2) ›

CF 1879F - Last Man Standing

We are given several independent game configurations, each describing a set of heroes. Each hero has two parameters: health and armor. The game proceeds in discrete rounds, and in every round we choose a fixed damage value x that stays constant for the entire simulation.
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Practice › Codeforces Solutions › Educational Codeforces Round 155 (Rated for Div. 2) ›

CF 1879A - Rigged!

We have a weightlifting competition with n athletes. Athlete i has strength si and endurance ei. A barbell weight w is chosen. Any athlete whose strength is less than w cannot lift the barbell at all. Any athlete whose strength is at least w lifts it exactly ei times.
codeforces competitive-programming greedy Jun 8, 2026
Practice › Codeforces Solutions › Educational Codeforces Round 155 (Rated for Div. 2) ›

CF 1879D - Sum of XOR Functions

We are given an array of non-negative integers. For every subarray $[l,r]$, we compute the XOR of all elements inside that subarray. Let that XOR value be $f(l,r)$. The contribution of a subarray is not just its XOR.
codeforces competitive-programming bitmasks combinatorics divide-and-conquer dp math Jun 8, 2026
Practice › Codeforces Solutions › Educational Codeforces Round 155 (Rated for Div. 2) ›

CF 1879E - Interactive Game with Coloring

We are given a rooted tree with $n$ vertices, where vertex 1 is the root. Each vertex $i 1$ has a parent $pi$, so the tree is naturally defined by this parent array.
codeforces competitive-programming brute-force constructive-algorithms dfs-and-similar graphs implementation interactive trees Jun 8, 2026
Practice › Codeforces Solutions › Educational Codeforces Round 155 (Rated for Div. 2) ›

CF 1879C - Make it Alternating

We are given a binary string, and we are allowed to delete characters from arbitrary positions. After deleting some characters, we want the remaining string to be alternating, meaning no two adjacent characters are equal.
codeforces competitive-programming combinatorics dp greedy Jun 8, 2026
Practice › Codeforces Solutions › Educational Codeforces Round 155 (Rated for Div. 2) ›

CF 1879B - Chips on the Board

We are given an $n times n$ grid and two arrays $a$ and $b$, each of length $n$. We want to place chips on some cells so that every cell shares a row or column with at least one chip. Placing a chip on cell $(i, j)$ costs $ai + bj$.
codeforces competitive-programming constructive-algorithms greedy Jun 8, 2026