Language: C++

#include <cstdio>
#include <iostream>
#include <cstdlib>
#include <string>
#include <cstring>
#include <set>
#include <map>
#include <queue>
#include <deque>
#include <stack>
#include <vector>
#include <ctime>
#include <cassert>
#include <cmath>
#include <algorithm>
#include <iomanip>
#include <fstream>
using namespace std;
#define F first
#define S second
#define pb push_back
#define mp make_pair
#define ll long long
#define ull unsigned long long
#define inf 1000000000
#define INF 1000000000000000000ll
const int N = 1e6;
const int mod = 1e9+7;

map<string,int>m;

int n, a[N];
int main() {
    cin >> n;
    for(int i = 1; i <= n; ++i){
        cin >> a[i];
        m[ a[i] ]++;
        if(m[ a[i] ] == 2){
            cout << "NO";
            return 0;
        }
    }
    cout << "YES";
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:37:10: error: no match for 'operator[]' (operand types are 'std::map<std::__cxx11::basic_string<char>, int>' and 'int')
   37 |         m[ a[i] ]++;
      |          ^
In file included from /usr/include/c++/14/map:63,
                 from a.cc:7:
/usr/include/c++/14/bits/stl_map.h:504:7: note: candidate: 'std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](const key_type&) [with _Key = std::__cxx11::basic_string<char>; _Tp = int; _Compare = std::less<std::__cxx11::basic_string<char> >; _Alloc = std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> >; mapped_type = int; key_type = std::__cxx11::basic_string<char>]'
  504 |       operator[](const key_type& __k)
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_map.h:504:34: note:   no known conversion for argument 1 from 'int' to 'const std::map<std::__cxx11::basic_string<char>, int>::key_type&' {aka 'const std::__cxx11::basic_string<char>&'}
  504 |       operator[](const key_type& __k)
      |                  ~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_map.h:524:7: note: candidate: 'std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](key_type&&) [with _Key = std::__cxx11::basic_string<char>; _Tp = int; _Compare = std::less<std::__cxx11::basic_string<char> >; _Alloc = std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> >; mapped_type = int; key_type = std::__cxx11::basic_string<char>]'
  524 |       operator[](key_type&& __k)
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_map.h:524:29: note:   no known conversion for argument 1 from 'int' to 'std::map<std::__cxx11::basic_string<char>, int>::key_type&&' {aka 'std::__cxx11::basic_string<char>&&'}
  524 |       operator[](key_type&& __k)
      |                  ~~~~~~~~~~~^~~
a.cc:38:13: error: no match for 'operator[]' (operand types are 'std::map<std::__cxx11::basic_string<char>, int>' and 'int')
   38 |         if(m[ a[i] ] == 2){
      |             ^
/usr/include/c++/14/bits/stl_map.h:504:7: note: candidate: 'std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](const key_type&) [with _Key = std::__cxx11::basic_string<char>; _Tp = int; _Compare = std::less<std::__cxx11::basic_string<char> >; _Alloc = std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> >; mapped_type = int; key_type = std::__cxx11::basic_string<char>]'
  504 |       operator[](const key_type& __k)
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_map.h:504:34: note:   no known conversion for argument 1 from 'int' to 'const std::map<std::__cxx11::basic_string<char>, int>::key_type&' {aka 'const std::__cxx11::basic_string<char>&'}
  504 |       operator[](const key_type& __k)
      |                  ~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_map.h:524:7: note: candidate: 'std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](key_type&&) [with _Key = std::__cxx11::basic_string<char>; _Tp = int; _Compare = std::less<std::__cxx11::basic_string<char> >; _Alloc = std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> >; mapped_type = int; key_type = std::__cxx11::basic_string<char>]'
  524 |       operator[](key_type&& __k)
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_map.h:524:29: note:   no known conversion for argument 1 from 'int' to 'std::map<std::__cxx11::basic_string<char>, int>::key_type&&' {aka 'std::__cxx11::basic_string<char>&&'}
  524 |       operator[](key_type&& __k)
      |                  ~~~~~~~~~~~^~~