A14414 | Subsequence Permutation
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内存限制256MB
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题目描述
A string $s$ of length $n$ , consisting of lowercase letters of the English alphabet, is given.
You must choose some number $k$ between $0$ and $n$ . Then, you select $k$ characters of $s$ and permute them however you want. In this process, the positions of the other $n-k$ characters remain unchanged. You have to perform this operation exactly once.
For example, if $s=\texttt{"andrea"}$ , you can choose the $k=4$ characters $\texttt{"a_d_ea"}$ and permute them into $\texttt{"d_e_aa"}$ so that after the operation the string becomes $\texttt{"dneraa"}$ .
Determine the minimum $k$ so that it is possible to sort $s$ alphabetically (that is, after the operation its characters appear in alphabetical order).
You must choose some number $k$ between $0$ and $n$ . Then, you select $k$ characters of $s$ and permute them however you want. In this process, the positions of the other $n-k$ characters remain unchanged. You have to perform this operation exactly once.
For example, if $s=\texttt{"andrea"}$ , you can choose the $k=4$ characters $\texttt{"a_d_ea"}$ and permute them into $\texttt{"d_e_aa"}$ so that after the operation the string becomes $\texttt{"dneraa"}$ .
Determine the minimum $k$ so that it is possible to sort $s$ alphabetically (that is, after the operation its characters appear in alphabetical order).
输入格式
The first line contains a single integer $t$ ( $1 \le t \le 1000$ ) — the number of test cases. Then $t$ test cases follow.
The first line of each test case contains one integer $n$ ( $1 \le n \le 40$ ) — the length of the string.
The second line of each test case contains the string $s$ . It is guaranteed that $s$ contains only lowercase letters of the English alphabet.
The first line of each test case contains one integer $n$ ( $1 \le n \le 40$ ) — the length of the string.
The second line of each test case contains the string $s$ . It is guaranteed that $s$ contains only lowercase letters of the English alphabet.
输出格式
For each test case, output the minimum $k$ that allows you to obtain a string sorted alphabetically, through the operation described above.
输入输出样例
输入 #1
4 3 lol 10 codeforces 5 aaaaa 4 dcba
输出 #1
2 6 0 4
In the first test case, we can choose the $k=2$ characters $\texttt{"_ol"}$ and rearrange them as $\texttt{"_lo"}$ (so the resulting string is $\texttt{"llo"}$ ). It is not possible to sort the string choosing strictly less than $2$ characters.
In the second test case, one possible way to sort $s$ is to consider the $k=6$ characters $\texttt{"_o__force_"}$ and rearrange them as $\texttt{"_c__efoor_"}$ (so the resulting string is $\texttt{"ccdeefoors"}$ ). One can show that it is not possible to sort the string choosing strictly less than $6$ characters.
In the third test case, string $s$ is already sorted (so we can choose $k=0$ characters).
In the fourth test case, we can choose all $k=4$ characters $\texttt{"dcba"}$ and reverse the whole string (so the resulting string is $\texttt{"abcd"}$ ).
In the second test case, one possible way to sort $s$ is to consider the $k=6$ characters $\texttt{"_o__force_"}$ and rearrange them as $\texttt{"_c__efoor_"}$ (so the resulting string is $\texttt{"ccdeefoors"}$ ). One can show that it is not possible to sort the string choosing strictly less than $6$ characters.
In the third test case, string $s$ is already sorted (so we can choose $k=0$ characters).
In the fourth test case, we can choose all $k=4$ characters $\texttt{"dcba"}$ and reverse the whole string (so the resulting string is $\texttt{"abcd"}$ ).
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