func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long int t;     cin >> t;     while (t--) {       long long int n, i, zer = -1, one;       cin >> n;       string s;       string ans =   ;       cin >> s;       for (i = 0; i < n; i++) {         if (s[i] ==  1 ) break;         zer = i;       }       one = n;       for (i = n - 1; i >= 0; i--) {         if (s[i] ==  0 ) break;         one = i;       }       for (i = 0; i <= zer; i++) ans = ans +  0 ;       if (zer + 1 != one) ans = ans +  0 ;       for (i = n - 1; i >= one; i--) ans = ans +  1 ;       cout << ans << endl;     }   }   