53.最大子序和

思路：用两个值分别记录当前一直连续加过来的最大值，还有一个记录整个数组的最大值，并适时更新他们得值

class Solution:
    def maxSubArray(self, nums: List[int]) -> int:
      	#初始化最大值，和当前值
        maxsum = nums[0]
        privousum = nums[0]
        for i in range(1, len(nums)):
            privousum = max(privousum + nums[i], nums[i])
            maxsum = max(maxsum, privousum)
        return maxsum

53.最大子序和