func_code_string: #include <bits/stdc++.h>   using namespace std;      #define ll long long   #define fi first   #define se second      const int MAX = 2 * 1e5 + 10;   const int MOD = 1e9 + 7;   ll t;   ll n, m, k;   ll a, b, x, y, x2, y2;   ll bio[MAX];   ll arr[MAX];   vector <ll> v;   string s;      int main() {       cin >> t;          while (t--) {           cin >> n;           cin >> s;              b = 0;           for (int i = 0; i < n; i++) {               if (s[i] ==  b ) b++;           }              for (int i = 0; i < b; i++) {               cout <<  b ;           }           for (int i = 0; i < n; i++) {               if (s[i] ==  b ) continue;               cout << s[i];           }              cout <<   n ;       }          return 0;   }   