Codeforces Round 189 (Div. 2)

2 problems from Codeforces Round 189 (Div. 2) (contest 320), difficulty 900-1500. 2/2 solutions verified against sample I/O.

2 items

Codeforces Round 189 (Div. 2)

Div. 2 | 2 problems | 2/2 verified | Difficulty 900-1500 | 2m 19s

# Problem Rating Tags Accepted Time ✓
A Magic Numbers 900 brute-force, greedy 45,409 1m 6s ✓
B Ping-Pong (Easy Version) 1500 dfs-and-similar, graphs 7,780 1m 13s ✓
Practice › Codeforces Solutions › Codeforces Round 189 (Div. 2) ›

CF 320A - Magic Numbers

We are given a single integer written in decimal form, and we must decide whether it can be constructed by repeatedly placing one of three fixed building blocks next to each other: 1, 14, and 144.
codeforces competitive-programming brute-force greedy Jun 6, 2026
Practice › Codeforces Solutions › Codeforces Round 189 (Div. 2) ›

CF 320B - Ping-Pong (Easy Version)

We are maintaining a growing collection of open intervals on the number line. Each time a new interval is added, it becomes a node in an implicit directed graph.
codeforces competitive-programming dfs-and-similar graphs Jun 6, 2026