Here is the interview question prompt, presented for reference.

Given an array of numbers, return true if there is a subarray that sums up to a certain number n.

A subarray is a contiguous subset of the array. For example the subarray of [1,2,3,4,5] is [1,2,3] or [3,4,5] or [2,3,4] etc.

const arr = [1, 2, 3], sum = 5
subarraySum(arr, sum)
// true
// [2, 3] sum up to 5

const arr = [11, 21, 4], sum = 9
subarraySum(arr, sum)
// false
// no subarrays sums up to 9

In the above examples, [2, 3] sum up to 5 so we return true. On the other hand, no subarray in [11, 21, 4] can sum up to 9.

Can you create a function subarraySum that accomplishes this?

Constraints

• Length of the array <= 100000
• The values in the array will be between 0 and 1000000000
• The target sum n will be between 0 and 1000000000
• The array can be empty
• Expected time complexity : O(n)
• Expected space complexity : O(n)

You can see the full challenge with visuals at this link.