Codeforces Beta Round 13

Solutions for Codeforces Beta Round 13 (contest 13). 5/5 problems verified against sample I/O. Difficulty range: 1000-2700.

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Codeforces Beta Round 13

Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1000-2700 | Time: 7m 43s

Problem Name Rating Tags Solve Time Verified
A Numbers 1000 implementation, math 1m 3s ✓
B Letter A 2000 geometry, implementation 1m 45s ✓
C Sequence 2200 dp, sortings 1m 24s ✓
D Triangles 2600 dp, geometry 1m 38s ✓
E Holes 2700 data-structures, dsu 1m 53s ✓
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CF 13A - Numbers

We are asked to compute the average sum of digits of a number _A_ when it is expressed in all bases from 2 up to _A_ - 1. The input is a single integer _A_ between 3 and 1000.
codeforces competitive-programming implementation math May 28, 2026
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CF 13B - Letter A

We are given three line segments on a 2D plane. We must decide whether these three segments can be interpreted as the shape of the capital letter A.
codeforces competitive-programming geometry implementation May 28, 2026
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CF 13C - Sequence

We are given a list of integers of length _N_, which may contain negative numbers, zeros, or large positive numbers. The task is to transform this list into a non-decreasing sequence, where each element is at least as large as the previous one.
codeforces competitive-programming dp sortings May 28, 2026
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CF 13D - Triangles

We have two sets of points on the plane. Red points may be used as triangle vertices, blue points are obstacles. No three points are collinear, which removes all degeneracies involving points on triangle borders.
codeforces competitive-programming dp geometry May 28, 2026
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CF 13E - Holes

We have a line of holes indexed from left to right. Every hole contains a jump length. If a ball is dropped into hole i, it immediately moves to i + a[i]. From there it jumps again using the value of the new hole, and this continues until the next jump leaves the array.
codeforces competitive-programming data-structures dsu May 28, 2026