Codeforces Round 809 (Div. 2)
A
Another String Minimization Problem
Codeforces
800
原题
←B →
翻译中…

You have a sequence $a_1, a_2, \ldots, a_n$ of length $n$, consisting of integers between $1$ and $m$. You also have a string $s$, consisting of $m$ characters B.

翻译中…

You are going to perform the following $n$ operations.

翻译中…
  • At the $i$-th ($1 \le i \le n$) operation, you replace either the $a_i$-th or the $(m + 1 - a_i)$-th character of $s$ with A. You can replace the character at any position multiple times through the operations.
翻译中…

Find the lexicographically smallest string you can get after these operations.

翻译中…

A string $x$ is lexicographically smaller than a string $y$ of the same length if and only if in the first position where $x$ and $y$ differ, the string $x$ has a letter that appears earlier in the alphabet than the corresponding letter in $y$.

翻译中…

Input

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The first line contains the number of test cases $t$ ($1 \le t \le 2000$).

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The first line of each test case contains two integers $n$ and $m$ ($1 \le n, m \le 50$) — the length of the sequence $a$ and the length of the string $s$ respectively.

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The second line contains $n$ integers $a_1, a_2, \ldots, a_n$ ($1 \le a_i \le m$) — the sequence $a$.

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Output

翻译中…

For each test case, print a string of length $m$ — the lexicographically smallest string you can get. Each character of the string should be either capital English letter A or capital English letter B.

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Note

翻译中…

In the first test case, the sequence $a = [1, 1, 3, 1]$. One of the possible solutions is the following.

翻译中…
  • At the $1$-st operation, you can replace the $1$-st character of $s$ with A. After it, $s$ becomes ABBBB.
  • At the $2$-nd operation, you can replace the $5$-th character of $s$ with A (since $m+1-a_2=5$). After it, $s$ becomes ABBBA.
  • At the $3$-rd operation, you can replace the $3$-rd character of $s$ with A. After it, $s$ becomes ABABA.
  • At the $4$-th operation, you can replace the $1$-st character of $s$ with A. After it, $s$ remains equal to ABABA.
翻译中…

The resulting string is

翻译中…

ABABA

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. It is impossible to produce a lexicographically smaller string.

翻译中…

In the second test case, you are going to perform only one operation. You can replace either the $2$-nd character or $4$-th character of $s$ with A. You can get strings BABBB and BBBAB after the operation. The string BABBB is the lexicographically smallest among these strings.

翻译中…

In the third test case, the only string you can get is A.

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In the fourth test case, you can replace the $1$-st and $2$-nd characters of $s$ with A to get AABB.

翻译中…

In the fifth test case, you can replace the $1$-st and $3$-rd characters of $s$ with A to get ABABBBB.

翻译中…

样例

Input #1
6
4 5
1 1 3 1
1 5
2
4 1
1 1 1 1
2 4
1 3
2 7
7 5
4 5
5 5 3 5
Output #1
ABABA
BABBB
A
AABB
ABABBBB
ABABA
InputCopy OutputCopy
题目信息
题号
1706A
时间限制
1 s
内存限制
256 MB
标签
2-SAT
构造
贪心
后缀结构
字符串

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。