I was asked the same question in an interview and they were epecting me to solve in O(n). Rest all solutions are solving in O(n^2) but this one is of order O(n).

This solution is wrong. It will never return 0, which is the answer for an array such as [20,10,-80,10,10,15,35]

very clearly!

Congrats! This is the fastest solution among the top ones

https://jsperf.com/codewars-equal-sides-of-an-array

I'm trying to understand why still but good work!

The problem stated that the array would have at least one value; no need to check if (len === 0) for this problem.

Also, it's not clear, but it might be that any array of less than 3 values might need to return -1. (The tests seem to only use arrays of length 3 or more.)

Clear and understandable, I like this solution

this seems way too easy to be a 4kyu ...

The empty list is a valid subarray. Sum of empty list is 0, greater than any negative number. 0 is the correct answer when the array only has negative elements.

Why should you return 0 if it's all negative? Why shouldn't the solution compute it accordingly? 0 is the wrong answer if it's an all negative int array.

This should have a complexity of O(n)