Language: C++

#include <stdio.h>
#include <iostream>
#include <vector>
#include <string>
#include <math.h>
#include <algorithm>
#include <cassert>
#include <map>
using namespace std;
#define ll long long
#define ui unsigned int
const double EPS = 1e-10;

bool asc(ui left,ui right) {
    return left > right;
}


int main(){
  ll n,ans;
  ans=0;
  cin>>n;
  vector<ui> a(n,0);
  for(ll i=0;i<n;i++){
    cin>>a[i];
  }
  sort(a.begin(),a.end(),asc);
  vector<int> b(n,0);
  multimap<ui, int> mp;
  for(int i=0;i<n;i++){
    mp.insert(make_pair(a[i],i));
  }
  for(ll i=0;i<n;i++){
    if(b[i]==1) continue;
    b[i]=1;
    int j;
    for(j=30;j>=0;j--){
      if(a[i]&(1<<j)) break;
    }
    ui x=(1<<(j+1))-a[i];
    auto itr=mp.find(x);
    for(auto l=itr;l<mp.end()&&x==l->first;l++){
      if(b[l->second]==0){
        ans++;
        b[l->second]=1;
        break;
      }
    }
  }
  cout<<ans<<endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:42:21: error: no match for 'operator<' (operand types are 'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >' and 'std::multimap<unsigned int, int>::iterator' {aka 'std::_Rb_tree<unsigned int, std::pair<const unsigned int, int>, std::_Select1st<std::pair<const unsigned int, int> >, std::less<unsigned int>, std::allocator<std::pair<const unsigned int, int> > >::iterator'})
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                    ~^~~~~~~~~
      |                    |       |
      |                    |       _Rb_tree_iterator<[...]>
      |                    _Rb_tree_iterator<[...]>
In file included from /usr/include/c++/14/string:48,
                 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,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:2:
/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:42:29: note:   'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >' is not derived from 'const std::reverse_iterator<_Iterator>'
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                             ^
/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:42:29: note:   'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >' is not derived from 'const std::reverse_iterator<_Iterator>'
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                             ^
/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:42:29: note:   'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >' is not derived from 'const std::move_iterator<_IteratorL>'
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                             ^
/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:42:29: note:   'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >' is not derived from 'const std::move_iterator<_IteratorL>'
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                             ^
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: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:42:29: note:   'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >' is not derived from 'const std::pair<_T1, _T2>'
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                             ^
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:673:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  673 |     operator< (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:673:5: note:   template argument deduction/substitution failed:
a.cc:42:29: note:   'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                             ^
/usr/include/c++/14/string_view:680:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  680 |     operator< (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:680:5: note:   template argument deduction/substitution failed:
a.cc:42:29: note:   'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                             ^
/usr/include/c++/14/string_view:688:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  688 |     operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:688:5: note:   template argument deduction/substitution failed:
a.cc:42:29: note:   'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3874:5: 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>&)'
 3874 |     operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3874:5: note:   template argument deduction/substitution failed:
a.cc:42:29: note:   'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3888:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3888 |     operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3888:5: note:   template argument deduction/substitution failed:
a.cc:42:29: note:   'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                             ^
/usr/include/c++/14/bits/basic_string.h:3901:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3901 |     operator<(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3901:5: note:   template argument deduction/substitution failed:
a.cc:42:29: note:   mismatched types 'const _CharT*' and 'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >'
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                             ^
In file included from /usr/include/c++/14/bits/memory_resource.h:47,
                 from /usr/include/c++/14/string:68:
/usr/include/c++/14/tuple:2600:5: note: candidate: 'template<class ... _TElements, class ... _UElements> constexpr bool std::operator<(const tuple<_UTypes ...>&, const tuple<_Elements ...>&)'
 2600 |     operator<(const tuple<_TElements...>& __t,
      |     ^~~~~~~~
/usr/include/c++/14/tuple:2600:5: note:   template argument deduction/substitution failed:
a.cc:42:29: note:   'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >' is not derived from 'const std::tuple<_UTypes ...>'
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                             ^
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:3:
/usr/include/c++/14/bits/stl_vector.h:2089:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::operator<(const vector<_Tp, _Alloc>&, const vector<_Tp, _Alloc>&)'
 2089 |     operator<(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:2089:5: note:   template argument deduction/substitution failed:
a.cc:42:29: note:   'std::_Rb_tree_iterator<std::pair<const unsigned int, int> >' is not derived from 'const std::vector<_Tp, _Alloc>'
   42 |     for(auto l=itr;l<mp.end()&&x==l->first;l++){
      |                             ^
In file included from /usr/include/c++/14/map:63,
                 from a.cc:8:
/usr/include/c++/14/bits/stl_map.h:1550:5: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator<(const map<_Key, _Tp, _Compare, _Allocator>&, const map<_Key, _Tp, _Compare, _Allocator>&)'
 1550 |     operator<(const map<_Key, _Tp, _Compare, _Alloc>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_map.h:1550:5: note:   template argument deduction/substitution failed:
a.cc:42:29: note:   'std::_Rb_tree_iterator<std::pair<const u