Codeforces Beta Round 26 (Codeforces format)

Solutions for Codeforces Beta Round 26 (Codeforces format) (contest 26). 4/5 problems verified against sample I/O. Difficulty range: 900-2400.

5 items

Codeforces Beta Round 26 (Codeforces format)

Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 900-2400 | Time: 7m 38s

Problem Name Rating Tags Solve Time Verified
A Almost Prime 900 number-theory 1m 18s ✓
B Regular Bracket Sequence 1400 greedy 1m 20s ✓
C Parquet 2000 combinatorics, constructive-algorithms, greedy 2m 9s ✗
D Tickets 2400 combinatorics, math, probabilities 1m 14s ✓
E Multithreading 2400 constructive-algorithms 1m 37s ✓
Practice › Codeforces Solutions › Codeforces Beta Round 26 (Codeforces format) ›

CF 26A - Almost Prime

We are asked to count numbers between 1 and that have exactly two distinct prime factors. For instance, 6 is almost prime because it can be factored as , and both 2 and 3 are prime. Numbers like 4 or 8 are not almost prime because they are powers of a single prime.
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Practice › Codeforces Solutions › Codeforces Beta Round 26 (Codeforces format) ›

CF 26B - Regular Bracket Sequence

We are given a string consisting solely of opening and closing parentheses. The task is to determine the maximum length of a subsequence that forms a valid, or regular, bracket sequence.
codeforces competitive-programming greedy May 28, 2026
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CF 26C - Parquet

We are asked to tile a rectangular floor of size n × m using three types of parquet planks. The first type is a 1×2 horizontal plank, the second is a 2×1 vertical plank, and the third is a 2×2 square plank.
codeforces competitive-programming combinatorics constructive-algorithms greedy implementation May 28, 2026
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CF 26D - Tickets

We have a ticket seller, Charlie, who sells race tickets costing 10 euros each. Customers arrive in some random order: some have only 10 euro banknotes, some have only 20 euro banknotes. Charlie initially has k 10 euro banknotes.
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CF 26E - Multithreading

Each process repeatedly executes two atomic instructions:
codeforces competitive-programming constructive-algorithms May 28, 2026