Language: C++

#include<bits/stdc++.h>
using namespace std;

bool check(int n);
int answer(vector<int> box, int t);

int main(void){
    long int n,x;
    vector<int> odd,even;
    cin >> n;
    for(long int i=0;i<n;i++){
        cin >> x;
        if(x%2){
            odd.push_back(x);
        }else{
            even.push_back(x);
        }
    }
    cout << answer(odd,0)+answer(even,0) << endl;
    return 0;
}
int answer(vector<int> box, long int t){
    long int s=box.size();
    long int n=t;
//    cout << s << endl;
    if(s<2) return t;
    int a,b;
    for(int i=0;i<s;i++){
        for(int j=i+1;j<s;j++){
            if(check(box.at(i)+box.at(j))){
                //cout <<" add " << box.at(i) <<" "<< box.at(j) << " " << t << endl;
                a=box.at(i);
                b=box.at(j);
                box.erase(box.begin()+i);
                box.erase(box.begin()+j-1);
                n=max(n,answer(box,t+1));
                box.insert(box.begin()+i,a);
                box.insert(box.begin()+j,b);
            }
        }
    }
    return n;
}

bool check(int n){
    while(n%2==0) n/=2;
    if(n==1){
        return 1;
    }else{
        return 0;
    }
}

Compiler output:
a.cc: In function 'int answer(std::vector<int>, long int)':
a.cc:36:22: error: no matching function for call to 'max(long int&, int)'
   36 |                 n=max(n,answer(box,t+1));
      |                   ~~~^~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:36:22: note:   deduced conflicting types for parameter 'const _Tp' ('long int' and 'int')
   36 |                 n=max(n,answer(box,t+1));
      |                   ~~~^~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61:
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:36:22: note:   mismatched types 'std::initializer_list<_Tp>' and 'long int'
   36 |                 n=max(n,answer(box,t+1));
      |                   ~~~^~~~~~~~~~~~~~~~~~~