Qwasar Silicon Valley

find pivot index from array of integers

Write a function that returns the pivot index of a given array of integers.

The pivot index is where the sum of the numbers on the left equal the sum of the numbers on the right.

If no such index exists, return -1.

If there are multiple pivot indexes, return the left-most pivot index.

Example:

Input: [1, 7, 3, 6, 5, 6]

Output: 3

Explanation:

The sum of the numbers to the left of index 3 (nums[3] = 6) is equal to the sum of numbers to the right of index 3.

Also, 3 is the first index where this occurs.

Input: [1, 2, 3]

Output: -1

Explanation:

There is no index that satisfies the conditions in the problem statement.