String and Operations

题意翻译

题目给定一个长度为 $n$ 的字符串，并且字符集为英文字母中的前 $k$ 个 在第 $i$ 个操作中，你将对最初在第 $i$ 个位置的字符进行以下操作： * $\text{L}$ 操作：将其与前一个字符交换（如果前一个字符存在 * $\text{R}$ 操作：将其与后一个字符交换（如果后一个字符存在 * $\text{D}$ 操作：将该字符替换为字符集中前一个字符（默认 $\text{a}$ 的前一个字符为第 $k$ 个英文字母 * $\text{U}$ 操作：将该字符替换为字符集中后一个字符（默认第 $k$ 个英文字母的后一个字符为 $\text{a}$ * $\text{O}$ 操作：什么都不做 给定字符串 $s$ 和 $k$ 的值，找到对 $s$ 进行一系列操作后可以得到的字典序最小的字符串。

题目描述

You are given a string $ s $ consisting of $ n $ characters. These characters are among the first $ k $ lowercase letters of the Latin alphabet. You have to perform $ n $ operations with the string. During the $ i $ -th operation, you take the character that initially occupied the $ i $ -th position, and perform one of the following actions with it: - swap it with the previous character in the string (if it exists). This operation is represented as L; - swap it with the next character in the string (if it exists). This operation is represented as R; - cyclically change it to the previous character in the alphabet (b becomes a, c becomes b, and so on; a becomes the $ k $ -th letter of the Latin alphabet). This operation is represented as D; - cyclically change it to the next character in the alphabet (a becomes b, b becomes c, and so on; the $ k $ -th letter of the Latin alphabet becomes a). This operation is represented as U; - do nothing. This operation is represented as 0. For example, suppose the initial string is test, $ k = 20 $ , and the sequence of operations is URLD. Then the string is transformed as follows: 1. the first operation is U, so we change the underlined letter in test to the next one in the first $ 20 $ Latin letters, which is a. The string is now aest; 2. the second operation is R, so we swap the underlined letter with the next one in the string aest. The string is now aset; 3. the third operation is L, so we swap the underlined letter with the previous one in the string aset (note that this is now the $ 2 $ -nd character of the string, but it was initially the $ 3 $ -rd one, so the $ 3 $ -rd operation is performed to it). The resulting string is saet; 4. the fourth operation is D, so we change the underlined letter in saet to the previous one in the first $ 20 $ Latin letters, which is s. The string is now saes. The result of performing the sequence of operations is saes. Given the string $ s $ and the value of $ k $ , find the lexicographically smallest string that can be obtained after applying a sequence of operations to $ s $ .

输入输出格式

输入格式

The first line contains one integer $ t $ ( $ 1 \le t \le 1000 $ ) — the number of test cases. Each test case consists of two lines. The first line contains two integers $ n $ and $ k $ ( $ 1 \le n \le 500 $ ; $ 2 \le k \le 26 $ ). The second line contains a string $ s $ consisting of $ n $ characters. Each character is one of the $ k $ first letters of the Latin alphabet (in lower case).

输出格式

For each test case, print one line containing the lexicographically smallest string that can be obtained from $ s $ using one sequence of operations.

输入输出样例

输入样例 #1

6
4 2
bbab
7 5
cceddda
6 5
ecdaed
7 4
dcdbdaa
8 3
ccabbaca
5 7
eabba

输出样例 #1

aaaa
baccacd
aabdac
aabacad
aaaaaaaa
abadb