func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long t;     cin >> t;     while (t--) {       long long n;       cin >> n;       string s, t;       cin >> s >> t;       long long w = 0;       char s1, t1, s2, t2;       int q = 0;       for (long long i = 0; i < n; i++) {         if (s[i] != t[i]) {           w++;         }         if (w == 1 && q == 0) {           s1 = s[i], t1 = t[i];           q++;         }         if (w == 2 && q == 1) {           s2 = s[i], t2 = t[i];           q++;         }       }       if (w != 2) {         cout <<  NO  << endl;       } else {         if (t1 == t2 && s1 == s2)           cout <<  yes  << endl;         else           cout <<  no  << endl;       }     }     return 0;   }   