Algorithm
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="andrea", you can choose the k=4 characters "a_d_ea" and permute them into "d_e_aa" so that after the operation the string becomes "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).
The first line contains a single integer t (1≤t≤1000) — the number of test cases. Then t test cases follow.
The first line of each test case contains one integer n (1≤n≤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.
For each test case, output the minimum k that allows you to obtain a string sorted alphabetically, through the operation described above.
4 3 lol 10 codeforces 5 aaaaa 4 dcba
2 6 0 4
In the first test case, we can choose the k=2 characters "_ol" and rearrange them as "_lo" (so the resulting string is "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 "_o__force_" and rearrange them as "_c__efoor_" (so the resulting string is "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 "dcba" and reverse the whole string (so the resulting string is "abcd").
Code Examples
#1 Code Example with C++ Programming
Code -
C++ Programming
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'
#define debug(n) cout<<(n)<<endl;
const ll INF = 2e18 + 99;
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int t;
cin>>t;
string s, k;
while(t--){
int n;
cin>>n;
cin>>s;
k = s;
sort(s.begin(), s.end());
int count = 0;
for(int i = 0; i < s.length(); i++){
if(s[i] != k[i]){
count++;
}
}
cout<<count<<endl;
}
}Input
3
lol
10v codeforces
5
aaaaa
4
dcba
Output
6
0
4
Demonstration
Codeforcess Solution 1552-A A. Subsequence Permutation ,C++, Java, Js and Python,1552-A,Codeforcess Solution