A13732 | $String Similarity$

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题目描述

A binary string is a string where each character is either 0 or 1. Two binary strings $a$ and $b$ of equal length are similar, if they have the same character in some position (there exists an integer $i$ such that $a_i = b_i$ ). For example: - 10010 and 01111 are similar (they have the same character in position $4$ ); - 10010 and 11111 are similar; - 111 and 111 are similar; - 0110 and 1001 are not similar. You are given an integer $n$ and a binary string $s$ consisting of $2n-1$ characters. Let's denote $s[l..r]$ as the contiguous substring of $s$ starting with $l$ -th character and ending with $r$ -th character (in other words, $s[l..r] = s_l s_{l + 1} s_{l + 2} \dots s_r$ ). You have to construct a binary string $w$ of length $n$ which is similar to all of the following strings: $s[1..n]$ , $s[2..n+1]$ , $s[3..n+2]$ , ..., $s[n..2n-1]$ .

The first line contains a single integer $t$ ( $1 \le t \le 1000$ ) — the number of test cases. The first line of each test case contains a single integer $n$ ( $1 \le n \le 50$ ). The second line of each test case contains the binary string $s$ of length $2n - 1$ . Each character $s_i$ is either 0 or 1.

For each test case, print the corresponding binary string $w$ of length $n$ . If there are multiple such strings — print any of them. It can be shown that at least one string $w$ meeting the constraints always exists.

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C++ 编辑器

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