0724-find-pivot-index.py

class Solution:
    def pivotIndex(self, nums: List[int]) -> int:
        total = sum(nums)  # O(n)

        leftSum = 0
        for i in range(len(nums)):
            rightSum = total - nums[i] - leftSum
            if leftSum == rightSum:
                return i
            leftSum += nums[i]
        return -1