func_code_string: #include <bits/stdc++.h>   using namespace std;   signed main() {     ios_base::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     long long k;     cin >> k;     map<char, long long> m;     for (long long g = 0; g < k; g++) {       long long n;       cin >> n;       string s, t;       cin >> s >> t;       m.clear();       for (long long i = 0; i < n; i++) {         m[s[i]]++;         m[t[i]]++;       }       bool found = 0;       for (map<char, long long>::iterator it = m.begin(); it != m.end(); it++)         if ((*it).second % 2 == 1) {           found = 1;           break;         }       if (found) {         cout <<  No n ;       } else {         cout <<  Yes n ;         vector<pair<long long, long long> > ans;         ans.clear();         for (long long i = 0; i < n; i++)           if (s[i] != t[i]) {             for (long long j = 0; j < n; j++)               if (i != j && t[j] != s[j]) {                 if (s[i] == s[j] || t[i] == t[j]) {                   swap(s[i], t[j]);                   ans.push_back({i, j});                   i = 0;                   break;                 }                 if (s[i] == t[j]) {                   swap(s[j], t[j]);                   swap(s[j], t[i]);                   ans.push_back({j, j});                   ans.push_back({j, i});                   i = 0;                   break;                 }                 if (t[i] == s[j]) {                   swap(s[j], t[j]);                   swap(s[i], t[j]);                   ans.push_back({j, j});                   ans.push_back({i, j});                   i = 0;                   break;                 }               }           }         cout << ans.size() << endl;         for (long long i = 0; i < ans.size(); i++)           cout << ans[i].first + 1 <<     << ans[i].second + 1 << endl;       }     }   }   