Add Numbers in array without any loop. I solved using recursion. Is there a better way?

Question

I was asked in an interview to add numbers in an array without using loop.

I solved it using recursion.

This is my solution

function addNumRecursively(nums){   
    return (nums.length > 1) ? (nums[0]  + addNumRecursively(nums.slice(1))) : nums[0];  
}

console.log(addNumRecursively([1,5,4]));

The output is

rahul@rahul:~/myPractise$ node Recurssion.js 
10

It's working fine.

Is there a better way ?

OK, maybe I didn't understand the question. `reduce` is a loop as well though. — Teemu, Jul 18 '16 at 06:25
What is your array size? Recursion will test your browser's stack size limit http://stackoverflow.com/questions/7826992/browser-javascript-stack-size-limit — gurvinder372, Jul 18 '16 at 06:26
@Teemu – Agree with you(`reduce` is loop as well).. No idea what Interviewer wanted to evaluate through this question.. — Rayon, Jul 18 '16 at 06:28
@Teemu - Is there a way to do this without an implicit loop? — nnnnnn, Jul 18 '16 at 06:28
@nnnnnn I doubt that would be possible. But like I said, I probably haven't fully understood the question. — Teemu, Jul 18 '16 at 06:32

score 2 · Answer 1 · answered Jul 18 '16 at 06:39

Reduce is a kind of a loop, just in disguise. Your recursive function application is fine for a solution i think.

If this is a javascript specific question and you wanted to be a little sneaky you could do

function sum(arr){
  return eval(arr.join('+'))
}

Yes eval is considered evil, yes its performance is poor but this could be an alternative solution

score 1 · Accepted Answer · answered Jul 18 '16 at 06:23

1

You can use Array reduce as below.

[0, 1, 2, 3, 4].reduce(function(prev, curr) {
  return prev + curr;
});

answered Jul 18 '16 at 06:23

Krishnakumar_Muraleedharan

439
3
13

score 0 · Answer 3 · answered Jul 18 '16 at 06:39

0

Javascript eval and join function will be useful for all array elements sum without using loop.

var total = eval([0, 1, 2, 3, 4].join("+"));
console.log(total);

answered Jul 18 '16 at 06:39

Rahul Patel

5,248
2
14
26

Add Numbers in array without any loop. I solved using recursion. Is there a better way?

3 Answers3