Language: C++

#include <stdio.h>
#include <iostream>
#include <string.h>
#include <unordered_map>
using namespace std;

int main(void)
{
	unordered_map<char, char> mp;
	
	int n;
	cin >> n;

	char cm[7] = "\0", str[13] = "\0";
	for (int i = 0; i < n; i++) {
		cin >> cm >> str;
		if (strcmp(cm, "insert") == 0) {
			mp["str"] = str;
		}
		else if (strcmp(cm, "find") == 0) {
			if (mp["str"]) cout << "yes";
			else cout << "no";
			cout << endl;
		}
	}

	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:18:27: error: ambiguous overload for 'operator[]' (operand types are 'std::unordered_map<char, char>' and 'const char [4]')
   18 |                         mp["str"] = str;
      |                           ^
In file included from /usr/include/c++/14/unordered_map:41,
                 from a.cc:4:
/usr/include/c++/14/bits/unordered_map.h:987:7: note: candidate: 'std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::mapped_type& std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::operator[](const key_type&) [with _Key = char; _Tp = char; _Hash = std::hash<char>; _Pred = std::equal_to<char>; _Alloc = std::allocator<std::pair<const char, char> >; mapped_type = char; key_type = char]' (near match)
  987 |       operator[](const key_type& __k)
      |       ^~~~~~~~
/usr/include/c++/14/bits/unordered_map.h:987:7: note:   conversion of argument 1 would be ill-formed:
a.cc:18:28: error: invalid conversion from 'const char*' to 'std::unordered_map<char, char>::key_type' {aka 'char'} [-fpermissive]
   18 |                         mp["str"] = str;
      |                            ^~~~~
      |                            |
      |                            const char*
/usr/include/c++/14/bits/unordered_map.h:991:7: note: candidate: 'std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::mapped_type& std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::operator[](key_type&&) [with _Key = char; _Tp = char; _Hash = std::hash<char>; _Pred = std::equal_to<char>; _Alloc = std::allocator<std::pair<const char, char> >; mapped_type = char; key_type = char]' (near match)
  991 |       operator[](key_type&& __k)
      |       ^~~~~~~~
/usr/include/c++/14/bits/unordered_map.h:991:7: note:   conversion of argument 1 would be ill-formed:
a.cc:18:28: error: invalid conversion from 'const char*' to 'std::unordered_map<char, char>::key_type' {aka 'char'} [-fpermissive]
   18 |                         mp["str"] = str;
      |                            ^~~~~
      |                            |
      |                            const char*
a.cc:21:31: error: ambiguous overload for 'operator[]' (operand types are 'std::unordered_map<char, char>' and 'const char [4]')
   21 |                         if (mp["str"]) cout << "yes";
      |                               ^
/usr/include/c++/14/bits/unordered_map.h:987:7: note: candidate: 'std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::mapped_type& std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::operator[](const key_type&) [with _Key = char; _Tp = char; _Hash = std::hash<char>; _Pred = std::equal_to<char>; _Alloc = std::allocator<std::pair<const char, char> >; mapped_type = char; key_type = char]' (near match)
  987 |       operator[](const key_type& __k)
      |       ^~~~~~~~
/usr/include/c++/14/bits/unordered_map.h:987:7: note:   conversion of argument 1 would be ill-formed:
a.cc:21:32: error: invalid conversion from 'const char*' to 'std::unordered_map<char, char>::key_type' {aka 'char'} [-fpermissive]
   21 |                         if (mp["str"]) cout << "yes";
      |                                ^~~~~
      |                                |
      |                                const char*
/usr/include/c++/14/bits/unordered_map.h:991:7: note: candidate: 'std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::mapped_type& std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::operator[](key_type&&) [with _Key = char; _Tp = char; _Hash = std::hash<char>; _Pred = std::equal_to<char>; _Alloc = std::allocator<std::pair<const char, char> >; mapped_type = char; key_type = char]' (near match)
  991 |       operator[](key_type&& __k)
      |       ^~~~~~~~
/usr/include/c++/14/bits/unordered_map.h:991:7: note:   conversion of argument 1 would be ill-formed:
a.cc:21:32: error: invalid conversion from 'const char*' to 'std::unordered_map<char, char>::key_type' {aka 'char'} [-fpermissive]
   21 |                         if (mp["str"]) cout << "yes";
      |                                ^~~~~
      |                                |
      |                                const char*