Find all the sets of length k in an array such that the sum of all the elements of set is equal to a given number S.

/*
    *  Array a[]      = Array to hold elements in set.
    *  howManyNoInSet = Size of set (k).
    *  size           = Elements in input array.
    *  sum            = Total sum of elements included in resulting set.
    *  spaceLeft      = Number of elements included in set currently.
    *  pos            = Index in input array.
    *  Total          = given number S.
    *  
    *  Eg.  Input : arr[] ={1,0,-1,2,-2,3}
    *  k = 3
    *  S = 0
    *  Sets :
    *  (1,0,-1)
    *  (0,2,-2)
    *         (-1,-2,3)
*/
 
/*
    *  RECURSIVE ALGORITHM
    *  1. if pos (current index of input array) is greater than equal to size of array 
    *     then return as it is not a valid element of input array.
    *  2. if set contains k(howManyNoInSet) elements and sum of these k elements = given Number S.
    *     i.e. if ( spaceLeft == 0 && sum == 0) then 
    *           we have found a solution.
    *  3. Else the solution doesn't matches our criteria and is discarded.
    *  4. Now, make 2 recursive calls:
    *   a. Not Including the current element in set. 
    *      RecurssiveSumCheck(pos+1, spaceLeft, sum)
    *   b. Including the current element in set.
    *      Since current element is included in set spaceLeft dicreases by 1 and sum also dicreases by value of current element.
    *      RecurssiveSumCheck(pos+1, spaceLeft-1, sum-arr[pos+1]);
*/
 
 
 
 
#include<iostream>
using namespace std;
int arr[]={-1,0,1,2,-2,4,-4,5,-5};
int size = sizeof(arr)/sizeof(arr[0]);
int *a;
int startIndex = -1, howManyNoInSet =3, Total = 0;
 
void RecurssiveSumCheck(int pos, int spaceLeft , int sum)
{
     if(pos >= size)
            return ;
     if(spaceLeft == 0 && sum == 0)
     {
          cout<<endl;
          for(int i =0;i<howManyNoInSet ; i++)
                                cout<<" "<<a[i];
          return ;
     }
     if(spaceLeft == 0 && sum !=0 )
        return;
     RecurssiveSumCheck(pos+1, spaceLeft, sum);
     a[howManyNoInSet-spaceLeft]=arr[pos+1];
     RecurssiveSumCheck(pos+1, spaceLeft-1, sum+arr[pos+1]);        
}
 
int main()
{
    a = new int[howManyNoInSet];
    RecurssiveSumCheck(startIndex,howManyNoInSet,Total);
}