【数组-简单】剑指 Offer II 012. 左右两边子数组的和相等

题目
代码

class Solution:
    def pivotIndex(self, nums: List[int]) -> int:
        ans=-1
        left,right=0,sum(nums)
        for idx,item in enumerate(nums):
            if left==(right-item):
                return idx
            else:
                left+=item
                right-=item
        return ans