Find Pivot Index Python Solution with Tests

lcpy gen -n 724   # by problem number
lcpy gen -s find_pivot_index   # by problem name

Input: nums = [1,7,3,6,5,6]
Output: 3
Explanation:
The pivot index is 3.
Left sum = nums[0] + nums[1] + nums[2] = 1 + 7 + 3 = 11
Right sum = nums[4] + nums[5] = 5 + 6 = 11

Input: nums = [1,2,3]
Output: -1
Explanation:
There is no index that satisfies the conditions in the problem statement.

Input: nums = [2,1,-1]
Output: 0
Explanation:
The pivot index is 0.
Left sum = 0 (no elements to the left of index 0)
Right sum = nums[1] + nums[2] = 1 + -1 = 0

class Solution:
    # Time: O(n)
    # Space: O(1)
    def pivot_index(self, nums: list[int]) -> int:
        total = sum(nums)
        left_sum = 0
        for i, val in enumerate(nums):
            if left_sum == total - left_sum - val:
                return i
            left_sum += val
        return -1