class Solution:
def pivotIndex(self, nums: List[int]) -> int:
l_sum, r_sum = 0, sum(nums) - nums[0]
if l_sum == r_sum:
return 0
for i in range(1, len(nums)):
l_sum += nums[i - 1]
r_sum -= nums[i]
if l_sum == r_sum:
return i
return -1