CODEWITHSUNDEEP
javaarraysrecursionsum
user3020469
user3020469

Reputation:

Find the sum of all elements in array recursively in java language

Here is my code:

public int sum(int[] array, int index) 
  {
    //int index is the number of elements in the array. 
       //Here is my base case:
    if (index == 0)
        return 0;
    //Now it's time for the recursion
    else
        return array[index] + sum(array, index + 1);
}

I keep on getting an out of bounds error, but I don't what I am doing wrong.

Upvotes: 0

Views: 18776

Answers (5)

Theresa Forster
Theresa Forster

Reputation: 1932

If you are using Java 1.8 you can do the following

public int sum(int[] array) 
{
     return (int)array.stream().sum();
}

or even 

public int sum(int[] array) 
{
     return (int)array.sum();
}

Upvotes: 0

Sumama Waheed
Sumama Waheed

Reputation: 3609

instead of going from 0 to highest index , go from highest index to 0, i did (index -1) because you said index is total elements, so if array has 10 elements, last element has index 9

public int sum(int[] array, int index) 
  {
    //int index is the number of elements in the array. 
       //Here is my base case:
    if (index == 0)
        return 0;
    //Now it's time for the recursion
    else
        return array[index-1] + sum(array, (index - 1);
}

Upvotes: 1

Timothy Do
Timothy Do

Reputation: 1

@ Masud - you're code has a logical error though (i'm beginner Java so sorry if i'm incorrect).

return array[index] + sum(array, index - 1);

     array[index]

will receive a out-of-bounds error as index starts at 0 - hence meaning there won't be an index there. 'index - 1' would work. Also, this would change your base case to return '0' as returning array[0] will have array[0] added twice and an incorrect sum.

This is my code:

public static int sumArrayRecursion(int array[], int n){
    if (n == 0){
        return 0;
    }
    else {
        return array[n-1] + sumArrayRecursion(array, n-1);
    }
}

Upvotes: 0

Rohit Jain
Rohit Jain

Reputation: 213243

Your base condition is faulty. It should be:

if (index == array.length)

Note, you need to pass index = 0 on first call. If you are passing index = array.length - 1, then keep the base case as it is, and change the recursive method invocation to pass index - 1, instead of index + 1.

However, do you really need recursion? I would seriously give it hundreds of thoughts before reaching out for recursion instead of loop for this task.

Upvotes: 8

Masudul
Masudul

Reputation: 21961

Try,

public static void main(String[] args){
    int arr[] = {3, 4, 6, 7};
    System.out.println(sum(arr, arr.length-1));

}

public static int sum(int[] array, int index) {
    if (index == 0) {
        return array[0];
    } else {
        return array[index] + sum(array, index - 1);
    }
}

Upvotes: 2

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