第三题在这里https://leetcode-cn.com/problems/contiguous-array/ 发一个python哈希表+前缀后解法  时间复杂度O(n) class Solution:     def findMaxLength(self, nums: List[int]) -> int:         lookup = {0:-1}         total = 0         max_len = 0         for i in range(len(nums)):             total += 1 if nums[i]==1 else -1             if total in lookup:                 max_len = max(max_len, i-lookup[total])             else:                 lookup[total]=i         return max_len