1864B - Swap and Reverse - CodeForces Solution

#include<iostream>
#include<vector>
#include<algorithm>
#include<math.h>
#include<queue>
#include<map>

using namespace std;

#define ll long long
#define all(x) (x).begin(), (x).end()

int main() {
    int t;
    cin >> t;
    while (t--)
    {
        int n, k;
        cin >> n >> k;
        string s;
        cin >> s;
        if(k % 2 == 0) {
            sort(all(s));
        }
        else {
            string e, o;
            for (int i = 0; i < n; i++)
            {
                if(i % 2 == 0) {
                    e.push_back(s[i]);
                }
                else {
                    o.push_back(s[i]);
                }
            }
            sort(all(e));
            sort(all(o));
            for (int i = 0; i < n; i+=2)
            {
                s[i] = e[i/2];
                s[i+1] = o[i/2];
            }
        }
        cout << s << endl;
    }
    return 0;
}