Language: C++

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
 
using namespace std;
using namespace __gnu_pbds;
 
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define fbo find_by_order
#define ook order_of_key
 
typedef long long ll;
typedef pair<int,int> ii;
typedef vector<int> vi;
typedef long double ld; 
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;
typedef set<int>::iterator sit;
typedef map<int,int>::iterator mit;
typedef vector<int>::iterator vit;

unordered_map<int,int> a[26];
unordered_map<int,int> b[26];

int x[51];
int main()
{
	ios_base::sync_with_stdio(0); cin.tie(0);
	int n, av; cin >> n >> av;
	for(int i = 0; i < n; i++)
	{
		cin >> x[i];
	}
	int l = n/2;
	int r = n - l;
	for(int i = 0; i < (1<<l); i++)
	{
		//if(i%100000==0) cout << i << endl;
		int bit = __builtin_popcount(i);
		int sum = 0;
		for(int j = 0; j < l; j++)
		{
			if(i&(1<<j)) sum += x[j];
		}
		a[bit][sum]++;
	}
	//cout << "PART 1 COMPLETE\n";
	for(int i = 0; i < (1<<r); i++)
	{
		int bit = __builtin_popcount(i);
		int sum = 0;
		for(int j = 0; j < r; j++)
		{
			if(i&(1<<j)) sum += x[j+l];
		}
		b[bit][sum]++;
	}
	//cout << "PART 2 COMPLETE\n";
	ll ans = 0;
	for(int i = 0; i <= l; i++)
	{
		for(map<int,int>::iterator it = a[i].begin(); it != a[i].end(); it++)
		{
			int sum = it->fi;
			//cout << sum << '\n';
			for(int k = 0; k < 26; k++)
			{
				if(i + k == 0) continue;
				ans += it->se*b[k][av*(i+k) - sum];
			}
		}
	}
	cout << ans;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:64:59: error: conversion from 'std::unordered_map<int, int>::iterator' {aka 'std::__detail::_Insert_base<int, std::pair<const int, int>, std::allocator<std::pair<const int, int> >, std::__detail::_Select1st, std::equal_to<int>, std::hash<int>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<false, false, true> >::iterator'} to non-scalar type 'std::map<int, int>::iterator' {aka 'std::_Rb_tree<int, std::pair<const int, int>, std::_Select1st<std::pair<const int, int> >, std::less<int>, std::allocator<std::pair<const int, int> > >::iterator'} requested
   64 |                 for(map<int,int>::iterator it = a[i].begin(); it != a[i].end(); it++)
      |                                                 ~~~~~~~~~~^~
a.cc:64:66: error: no match for 'operator!=' (operand types are 'std::map<int, int>::iterator' {aka 'std::_Rb_tree<int, std::pair<const int, int>, std::_Select1st<std::pair<const int, int> >, std::less<int>, std::allocator<std::pair<const int, int> > >::iterator'} and 'std::unordered_map<int, int>::iterator' {aka 'std::__detail::_Insert_base<int, std::pair<const int, int>, std::allocator<std::pair<const int, int> >, std::__detail::_Select1st, std::equal_to<int>, std::hash<int>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<false, false, true> >::iterator'})
   64 |                 for(map<int,int>::iterator it = a[i].begin(); it != a[i].end(); it++)
      |                                                               ~~ ^~ ~~~~~~~~~~
      |                                                               |             |
      |                                                               |             std::unordered_map<int, int>::iterator {aka std::__detail::_Insert_base<int, std::pair<const int, int>, std::allocator<std::pair<const int, int> >, std::__detail::_Select1st, std::equal_to<int>, std::hash<int>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<false, false, true> >::iterator}
      |                                                               std::map<int, int>::iterator {aka std::_Rb_tree<int, std::pair<const int, int>, std::_Select1st<std::pair<const int, int> >, std::less<int>, std::allocator<std::pair<const int, int> > >::iterator}
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1132:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator!=(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1132 |     operator!=(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1132:5: note:   template argument deduction/substitution failed:
a.cc:64:78: note:   'std::map<int, int>::iterator' {aka 'std::_Rb_tree<int, std::pair<const int, int>, std::_Select1st<std::pair<const int, int> >, std::less<int>, std::allocator<std::pair<const int, int> > >::iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   64 |                 for(map<int,int>::iterator it = a[i].begin(); it != a[i].end(); it++)
      |                                                                              ^
/usr/include/c++/14/bits/regex.h:1212:5: 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>&)'
 1212 |     operator!=(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1212:5: note:   template argument deduction/substitution failed:
a.cc:64:78: note:   'std::map<int, int>::iterator' {aka 'std::_Rb_tree<int, std::pair<const int, int>, std::_Select1st<std::pair<const int, int> >, std::less<int>, std::allocator<std::pair<const int, int> > >::iterator'} is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   64 |                 for(map<int,int>::iterator it = a[i].begin(); it != a[i].end(); it++)
      |                                                                              ^
/usr/include/c++/14/bits/regex.h:1305:5: 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>&)'
 1305 |     operator!=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1305:5: note:   template argument deduction/substitution failed:
a.cc:64:78: note:   'std::map<int, int>::iterator' {aka 'std::_Rb_tree<int, std::pair<const int, int>, std::_Select1st<std::pair<const int, int> >, std::less<int>, std::allocator<std::pair<const int, int> > >::iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   64 |                 for(map<int,int>::iterator it = a[i].begin(); it != a[i].end(); it++)
      |                                                                              ^
/usr/include/c++/14/bits/regex.h:1379:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator!=(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1379 |     operator!=(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1379:5: note:   template argument deduction/substitution failed:
a.cc:64:78: note:   'std::unordered_map<int, int>::iterator' {aka 'std::__detail::_Insert_base<int, std::pair<const int, int>, std::allocator<std::pair<const int, int> >, std::__detail::_Select1st, std::equal_to<int>, std::hash<int>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<false, false, true> >::iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   64 |                 for(map<int,int>::iterator it = a[i].begin(); it != a[i].end(); it++)
      |                                                                              ^
/usr/include/c++/14/bits/regex.h:1473:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator!=(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1473 |     operator!=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1473:5: note:   template argument deduction/substitution failed:
a.cc:64:78: note:   'std::map<int, int>::iterator' {aka 'std::_Rb_tree<int, std::pair<const int, int>, std::_Select1st<std::pair<const int, int> >, std::less<int>, std::allocator<std::pair<const int, int> > >::iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   64 |                 for(map<int,int>::iterator it = a[i].begin(); it != a[i].end(); it++)
      |                                                                              ^
/usr/include/c++/14/bits/regex.h:1547:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator!=(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1547 |     operator!=(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1547:5: note:   template argument deduction/substitution failed:
a.cc:64:78: note:   'std::unordered_map<int, int>::iterator' {aka 'std::__detail::_Insert_base<int, std::pair<const int, int>, std::allocator<std::pair<const int, int> >, std::__detail::_Select1st, std::equal_to<int>, std::hash<int>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<false, false, true> >::iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   64 |                 for(map<int,int>::iterator it = a[i].begin(); it != a[i].end(); it++)
      |                                                                              ^
/usr/include/c++/14/bits/regex.h:1647:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator!=(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1647 |     operator!=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1647:5: note:   template argument deduction/substitution failed:
a.cc:64:78: note:   'std::map<int, int>::iterator' {aka 'std::_Rb_tree<int, std::pair<const int, int>, std::_Select1st<std::pair<const int, int> >, std::less<int>, std::allocator<std::pair<const int, int> > >::iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   64 |                 for(map<int,int>::iterator it = a[i].begin(); it != a[i].end(); it++)
      |                                                                              ^
/usr/include/c++/14/bits/regex.h:2213:5: note: candidate: 'template<class _Bi_iter, class _Alloc> bool std::__cxx11::operator!=(const match_results<_BiIter, _Alloc>&, const match_results<_BiIter, _Alloc>&)'
 2213 |     operator!=(const match_results<_Bi_iter, _Alloc>& __m1,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:2213:5: note:   template argument deduction/substitution failed:
a.cc:64:78: note:   'std::map<int, int>::iterator' {aka 'std::_Rb_tree<int, std::pair<const int, int>, std::_Select1st<std::pair<const int, int> >, std::less<int>, std::allocator<std::pair<const int, int> > >::iterator'} is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
   64 |                 for(map<int,int>::iterator it = a[i].begin(); it != a[i].end(); 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:1052:5: note: candidate: 'template<class