1469E · A Bit Similar

Problem: Let's call two strings $a$ and $b$ (both of length $k$) a bit similar if they have the same character in some position, i. e. there exists at least one $i \in [1, k]$ such that $a_i = b_i$.

You are given a binary string $s$ of length $n$ (a string of $n$ characters 0 and/or 1) and an integer $k$. Let's denote the string $s[i..j]$ as the substring of $s$ starting from the $i$-th character and ending with the $j$-th character (that is, $s[i..j] = s_i s_{i + 1} s_{i + 2} \dots s_{j - 1} s_j$).

Let's call a binary string $t$ of length $k$ beautiful if it is a bit similar to all substrings of $s$ having length exactly $k$; that is, it is a bit similar to $s[1..k], s[2..k+1], \dots, s[n-k+1..n]$.

Your goal is to find the lexicographically smallest string $t$ that is beautiful, or report that no such string exists. String $x$ is lexicographically less than string $y$ if either $x$ is a prefix of $y$ (and $x \ne y$), or there exists such $i$ ($1 \le i \le \min(|x|, |y|)$), that $x_i < y_i$, and for any $j$ ($1 \le j < i$) $x_j = y_j$.

Input Format: The first line contains one integer $q$ ($1 \le q \le 10000$) — the number of test cases. Each test case consists of two lines.

The first line of each test case contains two integers $n$ and $k$ ($1 \le k \le n \le 10^6$). The second line contains the string $s$, consisting of $n$ characters (each character is either 0 or 1).

It is guaranteed that the sum of $n$ over all test cases does not exceed $10^6$.

Output Format: For each test case, print the answer as follows:

• if it is impossible to construct a beautiful string, print one line containing the string NO (note: exactly in upper case, you can't print No, for example);
• otherwise, print two lines. The first line should contain the string YES (exactly in upper case as well); the second line — the lexicographically smallest beautiful string, consisting of $k$ characters 0 and/or 1.