Given an array of integers, give an algorithm that returns the pivot index of this array. Pivot index is the index where the sum of the numbers to the left of the index is equal to the sum of the...

Given an array of integers, give an algorithm that returns the pivot index of this array. Pivot index is the index where the sum of the numbers to the left of the index is equal to the sum of the numbers to the right of the index. If no such index exists, we should return -1. If there are multiple pivot indexes, you should return the left-most pivot index.