Sum of array elements using recursion

Given an array of integers, find sum of array elements using recursion. 

Examples:

Input : A[] = {1, 2, 3}
Output : 6
1 + 2 + 3 = 6

Input : A[] = {15, 12, 13, 10}
Output : 50

We have discussed iterative solution in below post. 
Sum of elements in a given array

In this post, recursive solution is discussed. 

C++

// C++ program to find sum of array
// elements using recursion.
#include <stdio.h>

// Return sum of elements in A[0..N-1]
// using recursion.
int findSum(int A[], int N)
{
    if (N <= 0)
        return 0;
    return (findSum(A, N - 1) + A[N - 1]);
}

// Driver code
int main()
{
    int A[] = { 1, 2, 3, 4, 5 };
    int N = sizeof(A) / sizeof(A[0]);
    printf("%d", findSum(A, N));
    return 0;
}

Java

// Java program to find sum of array
// elements using recursion.

public class Test {
    static int arr[] = { 1, 2, 3, 4, 5 };

    // Return sum of elements in A[0..N-1]
    // using recursion.
    static int findSum(int A[], int N)
    {
        if (N <= 0)
            return 0;
        return (findSum(A, N - 1) + A[N - 1]);
    }

    // Driver method
    public static void main(String[] args)
    {
        System.out.println(findSum(arr, arr.length));
    }
}

Python3

# Python program to find sum of array
# elements using recursion.

 # Return sum of elements in A[0..N-1]
 # using recursion.
def _findSum(arr, N):
    if N <= 0:
        return 0
    else:
        return _findSum(arr, N - 1) + arr[N - 1]

# driver code
arr =[]
# input values to list
arr = [1, 2, 3, 4, 5]

# calculating length of array
N = len(arr)

ans =_findSum(arr,N)
print (ans)

# This code is contributed by Khare Ishita

C#

// C# program to find sum of array
// elements using recursion.
using System;

class Test {

    static int []arr = {1, 2, 3, 4, 5};

    // Return sum of elements in
    // A[0..N-1] using recursion.
    static int findSum(int []A, int N)
    {
        if (N <= 0)
            return 0;
        return (findSum(A, N - 1) + A[N - 1]);
    }

    // Driver Code
    public static void Main()
    {
        Console.Write(findSum(arr, arr.Length));
    }
}

// This code is contributed by Nitin Mittal.

PHP

<?php
// PHP program to find sum
// of array elements using
// recursion.

// Return sum of elements
// in A[0..N-1] using recursion.
function findSum($A, $N)
{
    if ($N <= 0)
        return 0;
    return (findSum($A, $N - 1) +
                    $A[$N - 1]);
}

// Driver code
$A = array(1, 2, 3, 4, 5);
$N = sizeof($A);
echo findSum($A, $N);

// This code is contributed
// by ihritik
?>

Javascript

<script>

// JavaScript program to find sum of array
// elements using recursion.

// Return sum of elements in A[0..N-1]
// using recursion.
function findSum(A, N) {
    if (N <= 0)
        return 0;
    return (findSum(A, N - 1) + A[N - 1]);
}

// Driver code

let A = [1, 2, 3, 4, 5];
let N = A.length;
document.write(findSum(A, N));

</script>

Output

15

Time Complexity; O(n)

Here n is the number of elements in the array.

Auxiliary Space: O(n)

The extra space is used in recursion call stack.

How does above recursive solution work?

This article is contributed by
Prakhar Agrawal.