Codeforces Round 1089 (Div. 2)

Solutions are presented as using the least memory and the fastest execution time. It also takes the top 10 most recent solutions from each language. If you want to limit to a specific index, click the "Solved" button and go to that problem.

ContestId
Name
Phase
Frozen
Duration (Seconds)
Relative Time
Start Time
2210 Codeforces Round 1089 (Div. 2) FINISHED False 8100 1610723 March 29, 2026, 2:35 p.m.

Problems

Solved
Index
Name
Type
Tags
Community Tag
Rating
( 297 ) E Binary Strings are Simple? PROGRAMMING constructive algorithms dsu interactive number theory

This is an interactive problem. You are given an unknown binary string (s)(^{\text{∗}}) of length (n). The function (f(l, r)) is defined as the number of distinct elements in the array (a) formed by the following operation: Let (S) be the substring (s_l s_{l+1} \ldots s_r). Let (m) be the length of the substring. We start with an empty array (a). For the (i)-th ((0 \le i \lt m)) left cyclic rotation(^{\text{†}}) of (S), let's denote the number of inversions(^{\text{‡}}) as (x_{i}). For every (i) such that (0 \le i \lt m), append (x_{i} \mbox{ mod } m) to the array (a), where (u \mbox{ mod } v) denotes the remainder of dividing (u) by (v). To determine (s), you can ask some questions. In each question, you can choose (2) integers (l) and (r) ((1 \le l \le r \le n)) and get the value of (f(l, r)). Asking each query incurs a cost of (\dfrac{n}{r-l+1}). Note that the cost does not necessarily have to be an integer. You have to determine the hidden binary string while keeping the total cost of queries atmost (\mathbf{max(30,3\cdot n)}). You are allowed to make at most (\mathbf{2}) guesses. (^{\text{∗}})A binary string only contains characters (0) and (1). (^{\text{†}})Let there be a binary string (s \; = \; s_{1}s_{2}\cdots s_{n}). The (k)-th left cyclic rotation of (s) is defined as (t_{k} \; = \; s_{k+1}s_{k+2}\cdots s_{n}s_{1}s_{2}\cdots s_{k}). (^{\text{‡}})Let there be a string (s \; = \; s_{1}s_{2}\cdots s_{n}). The number of inversions of (s) is defined as the number of pairs of indices (i,j \; (1 \le i \lt j \le n)), such that (s_{i} \gt s_{j}). Each test contains multiple test cases. The first line contains the number of test cases (t) ((1 \le t \le 100)). The description of the test cases follows. The first line of each test case contains a single integ

Tutorials

Codeforces Round 1089 (Div. 2) Editorial

Submissions

Submission Id
Author(s)
Index
Submitted
Verdict
Language
Test Set
Tests Passed
Time taken (ms)
Memory Consumed (bytes)
Tags
Rating
368765641 caffeine2ac E March 29, 2026, 4:44 p.m. OK C# 13 TESTS 23 93 14336000

remove filters

Back to search problems