Language: C++


#include <iostream>
#include <list>
#include <cmath>
#include <iterator>
#include <algorithm>

using namespace std;

int main() {
    int N;
    list<int> V;
    int A;
    list<int>::iterator itr;
    list<int>::iterator a;
    int answer = 0;
    
    
    cin >> N;
    
    for (int i = 0; i < N; i++) {
        cin >> A;
        V.push_back(A);
    }
    sort(V.begin() ,V.end());
    
    for (int i = 0; i < V.size(); i++) {
        itr = V.end();
        a = V.begin();
        if (V.size() % 2 == 0) {  //偶数なら
        advance(a, (V.size() / 2 - 1));
        }
        else if(V.size() % 2 == 1) {
                advance(a, (V.size() / 2));
        }
        
        answer += abs(*itr - *a);
        V.erase(a);
        V.erase(itr);
        
        }
    
    return 0;
}


Compiler output:
In file included from /usr/include/c++/14/algorithm:61,
                 from a.cc:6:
/usr/include/c++/14/bits/stl_algo.h: In instantiation of 'void std::__sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = _List_iterator<int>; _Compare = __gnu_cxx::__ops::_Iter_less_iter]':
/usr/include/c++/14/bits/stl_algo.h:4772:18:   required from 'void std::sort(_RAIter, _RAIter) [with _RAIter = _List_iterator<int>]'
 4772 |       std::__sort(__first, __last, __gnu_cxx::__ops::__iter_less_iter());
      |       ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
a.cc:25:9:   required from here
   25 |     sort(V.begin() ,V.end());
      |     ~~~~^~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algo.h:1906:50: error: no match for 'operator-' (operand types are 'std::_List_iterator<int>' and 'std::_List_iterator<int>')
 1906 |                                 std::__lg(__last - __first) * 2,
      |                                           ~~~~~~~^~~~~~~~~
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:618:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__y.base() - __x.base())) std::operator-(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  618 |     operator-(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:618:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/stl_algo.h:1906:50: note:   'std::_List_iterator<int>' is not derived from 'const std::reverse_iterator<_Iterator>'
 1906 |                                 std::__lg(__last - __first) * 2,
      |                                           ~~~~~~~^~~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__x.base() - __y.base())) std::operator-(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1790 |     operator-(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/stl_algo.h:1906:50: note:   'std::_List_iterator<int>' is not derived from 'const std::move_iterator<_IteratorL>'
 1906 |                                 std::__lg(__last - __first) * 2,
      |                                           ~~~~~~~^~~~~~~~~