Language: C++

#include <iostream>
#include <vector>
#include <algorithm>
#include <math.h>
using namespace std;

int main()
{
    int n;
    cin >> n;
    std::vector<long long int> a;
    std::vector<long long int> x;
    
    long long int sum = 0;
    for(int i=0; i<n; i++){
        long long int tmp;
        cin >> tmp;
        a.push_back(tmp);
        sum += tmp;
        x.push_back(sum);
        //cout << sum << "," << x[i] << endl;
    }

    long long int cnt = 0;
    long long int avg = 0;
    if(sum%2 == 0){  // 入力は2の倍数
       avg = sum/2;
        std::vector<int>::iterator itr = std::find(x.begin(), x.end(), avg);
        if(itr != x.end()){
            cout << cnt << endl;
            return 0;
        }
    }

    long double favg = (long double)sum/2.0;
    int index = 0; // 最初にavgを超えた
    for(int i=0; i<n; i++){
        if(x[i] > favg){
            index = i;
            break;
        }
    }
    if(index == n-1){
        /*
        while(1){
            sum--;
            cnt++;
            //cout << x[index-1] << "," << sum << "," << cnt << endl;
            if(sum%2 == 0 && sum/2 == x[index-1]){
                cout << cnt << endl;
                return 0;
            }
        }
        */
        cout << a[index] - x[index-1] << endl;
        return 0;
    }
    
    for(int i=0; i<index; i++){
        while(1){
            if(a[i] < 2) break;
            sum--;
            x[index]--;
            cnt++;
            //cout << x[index] << "," << sum << "," << cnt << endl;
            if(sum%2 == 0 && sum/2 == x[index]){
                cout << cnt << endl;
                return 0;
            }
        }
    }
    //cout << x[index] << "," << sum << "," << cnt << endl;
    /*
        while(1){
            sum++;
            x[index+1]--;
            cnt++;
            cout << x[index+1] << "," << sum << "," << cnt << endl;
            if(sum%2 == 0 && sum/2 == x[index]){
                cout << cnt << endl;
                return 0;
            }
        }
    */
    cout << x[index] - a[index+1] << endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:28:51: error: conversion from '__normal_iterator<long long int*,vector<long long int>>' to non-scalar type '__normal_iterator<int*,vector<int>>' requested
   28 |         std::vector<int>::iterator itr = std::find(x.begin(), x.end(), avg);
      |                                          ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
a.cc:29:16: error: no match for 'operator!=' (operand types are 'std::vector<int>::iterator' and 'std::vector<long long int>::iterator')
   29 |         if(itr != x.end()){
      |            ~~~ ^~ ~~~~~~~
      |            |           |
      |            |           __normal_iterator<long long int*,vector<long long int>>
      |            __normal_iterator<int*,vector<int>>
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:29:25: note:   'std::vector<int>::iterator' is not derived from 'const std::fpos<_StateT>'
   29 |         if(itr != x.end()){
      |                         ^
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:29:25: note:   'std::vector<int>::iterator' is not derived from 'const std::allocator<_CharT>'
   29 |         if(itr != x.end()){
      |                         ^
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:29:25: note:   'std::vector<int>::iterator' is not derived from 'const std::reverse_iterator<_Iterator>'
   29 |         if(itr != x.end()){
      |                         ^
/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:29:25: note:   'std::vector<int>::iterator' is not derived from 'const std::reverse_iterator<_Iterator>'
   29 |         if(itr != x.end()){
      |                         ^
/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:29:25: note:   'std::vector<int>::iterator' is not derived from 'const std::move_iterator<_IteratorL>'
   29 |         if(itr != x.end()){
      |                         ^
/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:29:25: note:   'std::vector<int>::iterator' is not derived from 'const std::move_iterator<_IteratorL>'
   29 |         if(itr != x.end()){
      |                         ^
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:29:25: note:   'std::vector<int>::iterator' is not derived from 'const std::pair<_T1, _T2>'
   29 |         if(itr != x.end()){
      |                         ^
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:29:25: note:   '__gnu_cxx::__normal_iterator<int*, std::vector<int> >' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   29 |         if(itr != x.end()){
      |                         ^
/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:29:25: note:   '__gnu_cxx::__normal_iterator<int*, std::vector<int> >' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   29 |         if(itr != x.end()){
      |                         ^
/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:29:25: note:   '__gnu_cxx::__normal_iterator<long long int*, std::vector<long long int> >' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   29 |         if(itr != x.end()){
      |                         ^
/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:29:25: note:   'std::vector<int>::iterator' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   29 |         if(itr != x.end()){
      |                         ^
/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:29:25: note:   mismatched types 'const _CharT*' and '__gnu_cxx::__normal_iterator<int*, std::vector<int> >'
   29 |         if(itr != x.end()){
      |                         ^
/usr/include/c++/14/bits/basic_string.h:3860:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator!=(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3860 |     operator!=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3860:5: note:   template argument deduction/substitution failed:
a.cc:29:25: note:   'std::vector<int>::iterator' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   29 |         if(itr != x.end()){
      |                         ^
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:2613:5: note: candidate: 'template<class ... _TElements, class ... _UElements> constexpr bool std::operator!=(const tuple<_UTypes ...>&, const tuple<_Elements ...>&)'
 2613 |     operator!=(const tuple<_TElements...>& __t,
      |     ^~~~~~~~
/usr/include/c++/14/tuple:2613:5: note:   template argument deduction/substitution failed:
a.cc:29:25: note:   'std::vector<int>::iterator' is not derived from 'const std::tuple<_UTypes ...>'
   29 |         if(itr != x.end()){
      |                         ^
In file included from /usr/include/c++/14/bits/locale_facets.h:48,
                 from /usr/include/c++/14/bits/basic_ios.h:37,
                 from /usr/include/c++/14/ios:46:
/usr/include/c++/14/bits/streambuf_iterator.h:242:5: note: candidate: 'template<class _CharT, class _Traits> bool std::operator!=(const istreambuf_iterator<_CharT, _Traits>&, const istreambuf_iterator<_CharT, _Traits>&)'
  242 |     operator!=(const istreambuf_iterator<_CharT, _Traits>& __a,
      |     ^~~~~~~~
/usr/include/c++/14/bits/streambuf_iter