Recursion Sum of Array

Question

I'm trying to print out the result of my returned sum but for some reason it prints out 0, but when I check the sum inside the function its performing its objective correctly. For example if I pass in an array of 10 items each equal to their index (0...9) the sum inside the function is 45 but when I print it out back in main() it prints 0. I'm really confused to say the least.

Here is my function, which I call using:

printf("%d\n", addArray3(arrayA, 9, 0));

To clarify, arrayA is a pointer to an 10 item'd array of integers.

// Sums array using recursion
int addArray3(int (*arrayA)[], int n, int sum){
    if (n<0){
        return sum; 
    } else {
        sum += (*arrayA)[n];
    }
    addArray3(arrayA, --n, sum);
}

If anyone can clear this up I'd really appreciate it, thanks!

Surely your compiler gives you a warning when you compile that code. Do not ignore the warnings! — kaylum
– kaylum, Commented Dec 31, 2015 at 6:52

Community · Accepted Answer · 2017-05-23 12:06:55Z

2

You are missing a return on the last line. Compile with all the warning on and it might find that for you.

Related question about this behaviour that covers whats going on here (not having a return): Implicit int return value of C function

edited May 23, 2017 at 12:06

CommunityBot

11 silver badge

answered Dec 31, 2015 at 6:53

CraigM

3992 silver badges5 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

bunty · Accepted Answer · 2015-12-31 07:16:25Z

0

Check this modified recursion function with efficient use of pointers:

void addArray3(int *arrayA, int n, int* sum){
    if (n<0){
        return;
    } else {
        *sum += arrayA[n];
    }
    addArray3(arrayA, --n, sum);
}

int main ()
{
    int ar[] = { 1, 2, 3};
    int sum = 0;
    addArray3(ar, 2, &sum);
    printf("%d\n",sum);

    return 0;
}

answered Dec 31, 2015 at 7:16

bunty

6295 silver badges9 bronze badges

Comments

Stubborn · Accepted Answer · 2015-12-31 07:08:17Z

-1

Try, like this,it's working for me in both the cases:

1) Storing the return value in int t. OR

2) Directly printing the return value.

#include <stdio.h>

int main()
{
        int a[10] = {0,1,2,3,4,5,6,7,8,9};
        int t;

//      t = addArray3(a,9,0);
//      printf("%d\n",t);
        printf("%d\n",addArray3(a,9,0));
}

int addArray3(int (*arrayA)[], int n, int sum)
{
        if (n<0)
        {
                return sum;
        }
        else
        {
                sum += (*arrayA)[n];
        }
        addArray3(arrayA, --n, sum);
}

answered Dec 31, 2015 at 7:08

Stubborn

7801 gold badge5 silver badges20 bronze badges

Collectives™ on Stack Overflow

Recursion Sum of Array

3 Answers 3

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related