724. Find Pivot Index

[fockspaces]

pivot 定義，不包含自己，左邊總和 = 右邊總和

1. 算出總和
2. 從頭開始 loop，累積 cur_sum
3. 當 cur_sum 和目標值 (target - num) / 2 相同，則 return index

class Solution:
    def pivotIndex(self, nums: List[int]) -> int:
        total, cur_sum = sum(nums), 0
        for i, num in enumerate(nums):
            if cur_sum == (total - num) / 2:
                return i
            cur_sum += num
        return -1