Codeforces Beta Round 9 (Div. 2 Only)

Solutions for Codeforces Beta Round 9 (Div. 2 Only) (contest 9). 5/5 problems verified against sample I/O. Difficulty range: 800-2300.

5 items

Codeforces Beta Round 9 (Div. 2 Only)

Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2300 | Time: 8m 20s

Problem Name Rating Tags Solve Time Verified
A Die Roll 800 math, probabilities 2m 43s ✓
B Running Student 1200 brute-force, geometry, implementation 1m 26s ✓
C Hexadecimal's Numbers 1200 brute-force, implementation, math 1m 10s ✓
D How many trees? 1900 combinatorics, divide-and-conquer, dp 1m 13s ✓
E Interestring graph and Apples 2300 dfs-and-similar, dsu, graphs 1m 48s ✓
Practice › Codeforces Solutions › Codeforces Beta Round 9 (Div. 2 Only) ›

CF 9A - Die Roll

We are asked to calculate the probability that Dot wins a simple dice game against Yakko and Wakko. Each character rolls a standard six-sided die. Dot wins if her roll is at least as large as the maximum of Yakko’s and Wakko’s rolls.
codeforces competitive-programming math probabilities May 28, 2026
Practice › Codeforces Solutions › Codeforces Beta Round 9 (Div. 2 Only) ›

CF 9B - Running Student

The student is already riding a bus that moves along the x-axis from left to right. The bus stops at fixed positions (xi, 0) in increasing order. At any stop except the first one, the student may get off and run directly to the university located at (xu, yu).
codeforces competitive-programming brute-force geometry implementation May 28, 2026
Practice › Codeforces Solutions › Codeforces Beta Round 9 (Div. 2 Only) ›

CF 9C - Hexadecimal's Numbers

We are asked to count how many numbers from 1 to n consist only of the digits 0 and 1 in their decimal representation. In other words, Hexadecimal's memory only stores numbers that, when written in base 10, contain no digits other than 0 or 1.
codeforces competitive-programming brute-force implementation math May 28, 2026
Practice › Codeforces Solutions › Codeforces Beta Round 9 (Div. 2 Only) ›

CF 9D - How many trees?

We are asked to count the number of distinct binary search trees (BSTs) that have exactly n nodes labeled from 1 to n, with the additional constraint that the height of each tree is at least h.
codeforces competitive-programming combinatorics divide-and-conquer dp May 28, 2026
Practice › Codeforces Solutions › Codeforces Beta Round 9 (Div. 2 Only) ›

CF 9E - Interestring graph and Apples

We start with an undirected multigraph. Multiple edges are allowed, and loops are also allowed. We may add new edges, and the goal is to transform the graph into a very specific structure.
codeforces competitive-programming dfs-and-similar dsu graphs May 28, 2026