Simple recursive Summing program

Question

Any tips on how to improve this simple recursion program?

#include <iostream>
#include <cstdlib>
using namespace std;
int findSum(int*, const int, int, int);
int main()
{
 int length = 5, sum = 0, n = 0;
 int list[length];
 for (n; n < length ; n++ )
 {
 list[n] = n + 1; //initializes array elements to 1,2,3,4,5
 }
 n = 0; 
 cout << findSum(list, length, n, sum) << endl;
 system("pause");
 return 0;
}
int findSum(int list[], const int length, int n, int sum)
{
 if (n == length) //if end of list has been reached, stop recursion
 {
 return sum;
 }
 else 
 {
 sum += list[n]; //adds list elements
 n++; //increments list
 return findSum(list, length, n, sum);
 }
}

• Loki Astari: Do you want to improve the recursion or do you want a better technique?
• mwmnj: Recursion must be used.

Answer 1

I think I'd prefer something like this:

int findsum(int const *list, int length) { 
 if (0 == length) 
 return 0;
 return list[0] + findsum(list+1, length-1);
}

This follows one of the typical recursive formulations -- basically a function that's almost like an inductive proof. Start by establishing a correct value for the simplest possible base case (or some obvious base case anyway), and then establish a pattern that's correct for some some sort of "Base+1" type of case.