How many subsets in the current set have all the elements but one sum up to the last element.

getset.cpp

#include <iostream>
#include <vector>

using namespace std;
int xcount = 0;

void getset( int i, int j, vector<int> nums, int sum){
    if( j >= i ) return ;
    if( sum+nums[j] == nums[i] ){
        xcount++;
        return;
    }

    if( sum + nums[j] < nums[i] )
        getset( i, j+1, nums, sum+nums[j]);

    if( sum < nums[i] )
        getset( i, j+1, nums, sum);

    return;
}

int main(){
    // hardcoded from the question, sorry
    int x[] = {3, 4, 9, 14, 15, 19, 28, 37, 47, 50, 54, 56, 59, 61, 70, 73, 78, 81, 92, 95, 97, 99};
    //int x[] = {1, 2, 3,4,5 };//, 4, 6};
    vector<int> nums(begin(x), end(x));

    int max = 1;
    int current = 0;
    // start at two, minimum number to get x+x=y
    for( int i = 2; i < nums.size(); ++i){
        getset(i,0,nums,0);
    }
    cout << xcount << endl;
    cin.get();
    return 0;
}