Codeforces Round 542 [Alex Lopashev Thanks-Round] (Div. 1)

Solutions for Codeforces Round 542 [Alex Lopashev Thanks-Round] (Div. 1) (contest 1129). 2/6 problems verified against sample I/O. Difficulty range: 1700-3100.

6 items

Codeforces Round 542 [Alex Lopashev Thanks-Round] (Div. 1)

Type: Div. 1 | Problems: 6 | Verified: 2/6 | Rating range: 1700-3100 | Time: 10m 27s

Problem Name Rating Tags Solve Time Verified
A1 Toy Train (Simplified) 1700 brute-force, greedy 1m 53s ✗
A2 Toy Train 1800 brute-force, greedy 1m 21s ✓
B Wrong Answer 2000 constructive-algorithms 2m 47s ✗
C Morse Code 2400 binary-search, data-structures, dp 1m 24s ✗
D Isolation 2900 data-structures, dp 1m 38s ✓
E Legendary Tree 3100 binary-search, interactive, trees 1m 24s ✗
Practice › Codeforces Solutions › Codeforces Round 542 [Alex Lopashev Thanks-Round] (Div. 1) ›

CF 1129E - Legendary Tree

We are asked to reconstruct an unknown tree of $n$ vertices by asking a limited type of query. The query is interactive: for any two disjoint, non-empty sets of vertices $S$ and $T$, and a chosen vertex $v$, we receive the number of pairs $(s, t) in S times T$ such that the…
codeforces competitive-programming binary-search interactive trees Jun 12, 2026
Practice › Codeforces Solutions › Codeforces Round 542 [Alex Lopashev Thanks-Round] (Div. 1) ›

CF 1129D - Isolation

We are asked to count how many ways we can split a given array of integers into contiguous, non-empty segments such that, in each segment, the number of integers that appear exactly once does not exceed a given threshold $k$.
codeforces competitive-programming data-structures dp Jun 12, 2026
Practice › Codeforces Solutions › Codeforces Round 542 [Alex Lopashev Thanks-Round] (Div. 1) ›

CF 1129B - Wrong Answer

We are asked to construct an array of integers such that a particular greedy algorithm gives a wrong answer by an exact amount.
codeforces competitive-programming constructive-algorithms Jun 12, 2026
Practice › Codeforces Solutions › Codeforces Round 542 [Alex Lopashev Thanks-Round] (Div. 1) ›

CF 1129C - Morse Code

We are asked to track sequences of English letters encoded in Morse code as we build a string incrementally, one character at a time. The string S starts empty and grows by adding either a dot (0) or a dash (1) at each step.
codeforces competitive-programming binary-search data-structures dp hashing sortings string-suffix-structures strings Jun 12, 2026
Practice › Codeforces Solutions › Codeforces Round 542 [Alex Lopashev Thanks-Round] (Div. 1) ›

CF 1129A1 - Toy Train (Simplified)

We have n stations arranged on a directed cycle. From station i, the train always moves to i + 1, and from station n it wraps back to station 1. Every move between neighboring stations costs exactly one second.
codeforces competitive-programming brute-force greedy Jun 12, 2026
Practice › Codeforces Solutions › Codeforces Round 542 [Alex Lopashev Thanks-Round] (Div. 1) ›

CF 1129A2 - Toy Train

We have a circular train network with n stations, numbered from 1 to n. A single train moves from one station to the next in order, looping back to station 1 after station n, taking exactly 1 second per move.
codeforces competitive-programming brute-force greedy Jun 12, 2026