Language: C++

#include<iostream>
#include<string>
#include<vector>
using namespace std;

int main(){
	int kc;
    vector<string> key;
	cin>>kc;
	key.resize(kc);
    for (int i = 0; i < kc; i++) cin>>key[i];
    bool isOpen = false;
    int oc;
	cin>>oc;
    for (int i = 0; i < oc; i++)
	{
        string tkey;
		cin>>tkey;
        bool isOK = false;
        for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
		{
			if(*ita==tkey)
			{
				isOK=true;
				break;
			}
		}		
        if (!isOK)
        {
            cout<<"Unknown "<<tkey<<endl;
        }
        else if (isOpen)
        {
            cout<<"Closed by "<<tkey<<endl;
            isOpen = false;
        }
        else
        {
            cout<<"Opened by "<<tkey<<endl;
            isOpen = true;
        }
	}
}

Compiler output:
a.cc: In function 'int main()':
a.cc:20:47: error: conversion from '<unresolved overloaded function type>' to non-scalar type 'std::vector<std::__cxx11::basic_string<char> >::iterator' requested
   20 |         for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
      |                                           ~~~~^~~~~
a.cc:20:56: error: no match for 'operator!=' (operand types are 'std::vector<std::__cxx11::basic_string<char> >::iterator' and '<unresolved overloaded function type>')
   20 |         for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
      |                                                     ~~~^~~~~~~~~
      |                                                     |        |
      |                                                     |        <unresolved overloaded function type>
      |                                                     std::vector<std::__cxx11::basic_string<char> >::iterator
In file included from /usr/include/c++/14/iosfwd:42,
                 from /usr/include/c++/14/ios:40,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/postypes.h:197:5: note: candidate: 'template<class _StateT> bool std::operator!=(const fpos<_StateT>&, const fpos<_StateT>&)'
  197 |     operator!=(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/postypes.h:197:5: note:   template argument deduction/substitution failed:
a.cc:20:62: note:   'std::vector<std::__cxx11::basic_string<char> >::iterator' is not derived from 'const std::fpos<_StateT>'
   20 |         for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
      |                                                              ^~~
In file included from /usr/include/c++/14/string:43,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44:
/usr/include/c++/14/bits/allocator.h:243:5: note: candidate: 'template<class _T1, class _T2> bool std::operator!=(const allocator<_CharT>&, const allocator<_T2>&)'
  243 |     operator!=(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/14/bits/allocator.h:243:5: note:   template argument deduction/substitution failed:
a.cc:20:62: note:   'std::vector<std::__cxx11::basic_string<char> >::iterator' is not derived from 'const std::allocator<_CharT>'
   20 |         for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
      |                                                              ^~~
In file included from /usr/include/c++/14/string:48:
/usr/include/c++/14/bits/stl_iterator.h:455:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator!=(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  455 |     operator!=(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:455:5: note:   template argument deduction/substitution failed:
a.cc:20:62: note:   'std::vector<std::__cxx11::basic_string<char> >::iterator' is not derived from 'const std::reverse_iterator<_Iterator>'
   20 |         for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
      |                                                              ^~~
/usr/include/c++/14/bits/stl_iterator.h:500:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator!=(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  500 |     operator!=(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:500:5: note:   template argument deduction/substitution failed:
a.cc:20:62: note:   'std::vector<std::__cxx11::basic_string<char> >::iterator' is not derived from 'const std::reverse_iterator<_Iterator>'
   20 |         for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
      |                                                              ^~~
/usr/include/c++/14/bits/stl_iterator.h:1686:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator!=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1686 |     operator!=(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1686:5: note:   template argument deduction/substitution failed:
a.cc:20:62: note:   'std::vector<std::__cxx11::basic_string<char> >::iterator' is not derived from 'const std::move_iterator<_IteratorL>'
   20 |         for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
      |                                                              ^~~
/usr/include/c++/14/bits/stl_iterator.h:1753:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator!=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1753 |     operator!=(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1753:5: note:   template argument deduction/substitution failed:
a.cc:20:62: note:   'std::vector<std::__cxx11::basic_string<char> >::iterator' is not derived from 'const std::move_iterator<_IteratorL>'
   20 |         for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
      |                                                              ^~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/string:51:
/usr/include/c++/14/bits/stl_pair.h:1052:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator!=(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1052 |     operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1052:5: note:   template argument deduction/substitution failed:
a.cc:20:62: note:   'std::vector<std::__cxx11::basic_string<char> >::iterator' is not derived from 'const std::pair<_T1, _T2>'
   20 |         for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
      |                                                              ^~~
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54:
/usr/include/c++/14/string_view:651:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  651 |     operator!=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:651:5: note:   template argument deduction/substitution failed:
a.cc:20:62: note:   '__gnu_cxx::__normal_iterator<std::__cxx11::basic_string<char>*, std::vector<std::__cxx11::basic_string<char> > >' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   20 |         for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
      |                                                              ^~~
/usr/include/c++/14/string_view:658:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  658 |     operator!=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:658:5: note:   template argument deduction/substitution failed:
a.cc:20:62: note:   '__gnu_cxx::__normal_iterator<std::__cxx11::basic_string<char>*, std::vector<std::__cxx11::basic_string<char> > >' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   20 |         for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
      |                                                              ^~~
/usr/include/c++/14/string_view:666:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  666 |     operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:666:5: note:   template argument deduction/substitution failed:
a.cc:20:62: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'std::vector<std::__cxx11::basic_string<char> >::const_iterator (std::vector<std::__cxx11::basic_string<char> >::*)() const noexcept'
   20 |         for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
      |                                                              ^~~
a.cc:20:62: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'std::vector<std::__cxx11::basic_string<char> >::iterator (std::vector<std::__cxx11::basic_string<char> >::*)() noexcept'
a.cc:20:62: note:   couldn't deduce template parameter '_CharT'
/usr/include/c++/14/bits/basic_string.h:3833:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator!=(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3833 |     operator!=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3833:5: note:   template argument deduction/substitution failed:
a.cc:20:62: note:   'std::vector<std::__cxx11::basic_string<char> >::iterator' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   20 |         for (vector<string>::iterator ita=key.begin;ita!=key.end;++ita)
      |                                                              ^~~
/usr/include/c++/14/bits/basic_string.h:3847:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator!=(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3847 |     operator!=(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3847:5: note:   template argument deduction/substitution failed:
a.cc:20:62: note:   mismatched types 'const _CharT*' and '__gnu_cxx::__normal_iterator<std::__cxx11::basic_string<char>*, std::vector<std::__cxx11::basic_string<char> > >'
   20 |