Codeforces Round 247 (Div. 2)

Solutions for Codeforces Round 247 (Div. 2) (contest 431). 5/5 problems verified against sample I/O. Difficulty range: 800-2200.

5 items

Codeforces Round 247 (Div. 2)

Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2200 | Time: 8m 37s

Problem Name Rating Tags Solve Time Verified
A Black Square 800 implementation 1m 10s ✓
B Shower Line 1200 brute-force, implementation 1m 52s ✓
C k-Tree 1600 dp, implementation, trees 1m 31s ✓
D Random Task 2100 binary-search, bitmasks, combinatorics 2m 1s ✓
E Chemistry Experiment 2200 binary-search, data-structures, ternary-search 2m 3s ✓
Practice › Codeforces Solutions › Codeforces Round 247 (Div. 2) ›

CF 431A - Black Square

In "Black Square," Jury must press on one of four vertical strips whenever a black square appears. Each strip has a fixed energy cost, measured in calories, for pressing it.
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Practice › Codeforces Solutions › Codeforces Round 247 (Div. 2) ›

CF 431B - Shower Line

We have exactly five students standing in a line for a shower. While one student is showering, the remaining students wait in line and talk in adjacent pairs. The first and second students talk, the third and fourth students talk, and so on.
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Practice › Codeforces Solutions › Codeforces Round 247 (Div. 2) ›

CF 431C - k-Tree

We are working with a rooted infinite tree where every node always has exactly $k$ outgoing edges to children. Each of those $k$ edges has a fixed weight: the first is 1, the second is 2, and so on up to $k$.
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Practice › Codeforces Solutions › Codeforces Round 247 (Div. 2) ›

CF 431D - Random Task

We need to find a positive integer n such that inside the interval (n, 2n], exactly m numbers have exactly k ones in their binary representation.
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Practice › Codeforces Solutions › Codeforces Round 247 (Div. 2) ›

CF 431E - Chemistry Experiment

We are given a set of containers, each containing some fixed amount of mercury. Over time, two kinds of operations happen. The first operation changes the mercury amount in a single container.
codeforces competitive-programming binary-search data-structures ternary-search May 29, 2026