Problem of The Day: Find Pivot Index

Problem Statement

leetcode problem link

My Solution [Accepted]

class Solution:
    def pivotIndex(self, nums: List[int]) -> int:
        prefix = []
        curr_sum = 0
        total_sum = sum(nums)
        for i, num in enumerate(nums):
            if total_sum - curr_sum - num == curr_sum:
                return i
            curr_sum += num
        return -1

Editorial

Approach #1: Prefix Sum [Accepted]

class Solution(object):
    def pivotIndex(self, nums):
        S = sum(nums)
        leftsum = 0
        for i, x in enumerate(nums):
            if leftsum == (S - leftsum - x):
                return i
            leftsum += x
        return -1