Given an integer array
nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.Example:
Input: [-2,1,-3,4,-1,2,1,-5,4],
Output: 6
Explanation: [4,-1,2,1] has the largest sum = 6.解法：
class Solution:
def maxSubArray(self, nums: 'List[int]') -> 'int':
if not nums:
return 0
curSum = maxSum = nums[0]
for num in nums[1:]:
curSum = max(num, curSum + num)
maxSum = max(maxSum, curSum)
return maxSum说明：
cursum是计算累加的数值和 与当前的数值大小之间的最大值，如果过去遍历的数据的累加和都没有现在的值大，那么过去累加的数据都没有任何的意义
maxsum就是不断的计算cursum的最大值，返回最终的结果
