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CF1864B.Swap and Reverse
Swap and Reverse
You are given a string of length consisting of lowercase English letters, and an integer . In one step you can perform any one of the two operations below:
- Pick an index () and swap and .
- Pick an index () and reverse the order of letters formed by the range of the string. Formally, if the string currently is equal to $s_1\ldots s_{i-1}s_is_{i+1}\ldots s_{i+k-2}s_{i+k-1}s_{i+k}\ldots s_{n-1}s_n$, change it to $s_1\ldots s_{i-1}s_{i+k-1}s_{i+k-2}\ldots s_{i+1}s_is_{i+k}\ldots s_{n-1}s_n$.
You can make as many steps as you want (possibly, zero). Your task is to find the lexicographically smallest string you can obtain after some number of steps.
A string is lexicographically smaller than a string of the same length if and only if the following holds:
- in the first position where and differ, the string has a letter that appears earlier in the alphabet than the corresponding letter in .
Input
Each test contains multiple test cases. The first line contains the number of test cases (). The description of the test cases follows.
The first line of each test case contains two integers and ().
The second line of each test case contains the string of length consisting of lowercase English letters.
It is guaranteed that the sum of over all test cases does not exceed .
Output
For each test case, print the lexicographically smallest string after doing some (possibly, zero) steps.
Note
In the first test case, we can obtain the string "aimn" using the following operations:
- Reverse the range . The string turns into "
niam". - Swap and . The string turns into "
ainm". - Reverse the range . The string turns into "
aimn".
It can be proven that we cannot obtain any string lexicographically smaller than "aimn". Therefore, "aimn" is the answer.
In the second test case, we can obtain the string "aandp" using the following operations:
- Swap and . The string turns into "
paadn". - Swap and . The string turns into "
aapdn". - Swap and . The string turns into "
aandp".
It can be proven that we cannot obtain any string lexicographically smaller than "aandp". Therefore, "aandp" is the answer.
Samples
5
4 2
nima
5 3
panda
9 2
theforces
7 3
amirfar
6 4
rounds
aimn
aandp
ceefhorst
aafmirr
dnorsu
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