func_code_string: #include <bits/stdc++.h>   using namespace std;   const int INF = 0x3f3f3f3f;   const long long int LINF = 0x3f3f3f3f3f3f3f;   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     int k;     cin >> k;     string second, t;     int freq[130];     while (k--) {       memset(freq, 0, sizeof(freq));       int n;       vector<pair<int, int> > ans;       cin >> n;       cin >> second >> t;       for (int i = 0; i < n; i++) {         freq[second[i]]++;         freq[t[i]]++;       }       for (int i = 0; i < 130; i++) {         if (freq[i] % 2) {           cout <<  No                 <<   n ;           goto fim;         }       }       for (int i = 0; i < n; i++) {         if (second[i] == t[i]) continue;         int opa = 0;         for (int j = i + 1; j < n; j++)           if (second[j] == second[i]) {             swap(second[j], t[i]);             ans.push_back({j, i});             opa = 1;             break;           }         if (opa) continue;         for (int j = i + 1; j < n; j++) {           if (second[i] == t[j]) {             swap(second[j], t[j]);             ans.push_back({j, j});             swap(t[i], second[j]);             ans.push_back({j, i});             break;           }         }       }       cout <<  Yes             <<   n ;       cout << ans.size() <<   n ;       for (auto a : ans) cout << a.first + 1 <<     << a.second + 1 << endl;     fim:       continue;     }   }   