Language: C++

#include<bits/stdc++.h>
#include<string>
#include<set>
#include<iterator>
using namespace std;
int freq(set<char>::iterator it,string s)
{
  int ans=0;
  for(int i=0;i<s.length();i++)
  {
    if(*it == s[i])
      ans++;
  }
  return ans;
}
int main()
{
  string s;
  cin >> s;int f;int cnt=0;
  set<char> k;set<char>::iterator it = k.begin();
  for(int i=0;i<s.length();i++)
    k.insert(s[i]);
  for( it=0;it<k.size();it++)
  {
      f = freq(it,s);.
    if(!(f&1))
      cnt=cnt+f;
  }
  if(cnt == s.length())
    cout<<"YES"<<endl;
  else
    cout<<"NO"<<endl;
      
  return 0;
}
  

Compiler output:
a.cc: In function 'int main()':
a.cc:23:11: error: no match for 'operator=' (operand types are 'std::set<char>::iterator' {aka 'std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator'} and 'int')
   23 |   for( it=0;it<k.size();it++)
      |           ^
In file included from /usr/include/c++/14/map:62,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:152,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_tree.h:324:12: note: candidate: 'constexpr std::_Rb_tree_const_iterator<char>& std::_Rb_tree_const_iterator<char>::operator=(const std::_Rb_tree_const_iterator<char>&)'
  324 |     struct _Rb_tree_const_iterator
      |            ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_tree.h:324:12: note:   no known conversion for argument 1 from 'int' to 'const std::_Rb_tree_const_iterator<char>&'
/usr/include/c++/14/bits/stl_tree.h:324:12: note: candidate: 'constexpr std::_Rb_tree_const_iterator<char>& std::_Rb_tree_const_iterator<char>::operator=(std::_Rb_tree_const_iterator<char>&&)'
/usr/include/c++/14/bits/stl_tree.h:324:12: note:   no known conversion for argument 1 from 'int' to 'std::_Rb_tree_const_iterator<char>&&'
a.cc:23:15: error: no match for 'operator<' (operand types are 'std::set<char>::iterator' {aka 'std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator'} and 'std::set<char>::size_type' {aka 'long unsigned int'})
   23 |   for( it=0;it<k.size();it++)
      |             ~~^~~~~~~~~
      |             |        |
      |             |        std::set<char>::size_type {aka long unsigned int}
      |             std::set<char>::iterator {aka std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator}
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181:
/usr/include/c++/14/bits/regex.h:1143:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1143 |     operator<(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1143:5: note:   template argument deduction/substitution failed:
a.cc:23:23: note:   'std::set<char>::iterator' {aka 'std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   23 |   for( it=0;it<k.size();it++)
      |                       ^
/usr/include/c++/14/bits/regex.h:1224:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1224 |     operator<(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1224:5: note:   template argument deduction/substitution failed:
a.cc:23:23: note:   'std::set<char>::iterator' {aka 'std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator'} is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   23 |   for( it=0;it<k.size();it++)
      |                       ^
/usr/include/c++/14/bits/regex.h:1317:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1317 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1317:5: note:   template argument deduction/substitution failed:
a.cc:23:23: note:   'std::set<char>::iterator' {aka 'std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   23 |   for( it=0;it<k.size();it++)
      |                       ^
/usr/include/c++/14/bits/regex.h:1391:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1391 |     operator<(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1391:5: note:   template argument deduction/substitution failed:
a.cc:23:23: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'std::set<char>::size_type' {aka 'long unsigned int'}
   23 |   for( it=0;it<k.size();it++)
      |                       ^
/usr/include/c++/14/bits/regex.h:1485:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1485 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1485:5: note:   template argument deduction/substitution failed:
a.cc:23:23: note:   'std::set<char>::iterator' {aka 'std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   23 |   for( it=0;it<k.size();it++)
      |                       ^
/usr/include/c++/14/bits/regex.h:1560:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1560 |     operator<(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1560:5: note:   template argument deduction/substitution failed:
a.cc:23:23: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'std::set<char>::size_type' {aka 'long unsigned int'}
   23 |   for( it=0;it<k.size();it++)
      |                       ^
/usr/include/c++/14/bits/regex.h:1660:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1660 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1660:5: note:   template argument deduction/substitution failed:
a.cc:23:23: note:   'std::set<char>::iterator' {aka 'std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   23 |   for( it=0;it<k.size();it++)
      |                       ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1045:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator<(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1045 |     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1045:5: note:   template argument deduction/substitution failed:
a.cc:23:23: note:   'std::set<char>::iterator' {aka 'std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator'} is not derived from 'const std::pair<_T1, _T2>'
   23 |   for( it=0;it<k.size();it++)
      |                       ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:448:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  448 |     operator<(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:448:5: note:   template argument deduction/substitution failed:
a.cc:23:23: note:   'std::set<char>::iterator' {aka 'std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator'} is not derived from 'const std::reverse_iterator<_Iterator>'
   23 |   for( it=0;it<k.size();it++)
      |                       ^
/usr/include/c++/14/bits/stl_iterator.h:493:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  493 |     operator<(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note:   template argument deduction/substitution failed:
a.cc:23:23: note:   'std::set<char>::iterator' {aka 'std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator'} is not derived from 'const std::reverse_iterator<_Iterator>'
   23 |   for( it=0;it<k.size();it++)
      |                       ^
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1694 |     operator<(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note:   template argument deduction/substitution failed:
a.cc:23:23: note:   'std::set<char>::iterator' {aka 'std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator'} is not derived from 'const std::move_iterator<_IteratorL>'
   23 |   for( it=0;it<k.size();it++)
      |                       ^
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1760 |     operator<(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note:   template argument deduction/substitution failed:
a.cc:23:23: note:   'std::set<char>::iterator' {aka 'std::_Rb_tree<char, char, std::_Identity<char>, std::less<char>, std::allocator<char> >::const_iterator'} is not derived from 'const std::move_iterator<_IteratorL>'
   23 |   for( it=0;it<k.size();it++)
      |                       ^
In file included fro