func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 2e5 + 5;   const long long MAX = 1e9 + 7;   int main() {     ios::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     int n;     cin >> n;     int a[n];     set<int> s;     for (int i = 0; i < n; i++) s.insert(i + 1);     for (int i = 0; i < n; i++) {       cin >> a[i];       if (a[i]) s.erase(a[i]);     }     int prev = -1;     for (int i = 0; i < n; i++) {       if (a[i] == 0) {         auto it = s.begin();         while (it != s.end() && *it == (i + 1)) it++;         if (it == s.end()) {           it = s.begin();           a[i] = a[prev];           a[prev] = *it;         } else {           a[i] = *it;           s.erase(it);           prev = i;         }       }     }     for (int i = 0; i < n; i++) {       cout << a[i] <<    ;     }     cout <<   n ;     return 0;   }   