[LeetCode]题解（python）：053-Maximum Subarray

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题目来源

https://leetcode.com/problems/maximum-subarray/

Find the contiguous subarray within an array (containing at least one number) which has the largest sum.

For example, given the array [−2,1,−3,4,−1,2,1,−5,4],
the contiguous subarray [4,−1,2,1] has the largest sum = 6.

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题意分析

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Input: a list

Output: a number

Conditions:求最大连续子序列的和

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题目思路

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这题有点像动态规划，但是发现不需要索引之类的，所以想直接知道以某个值为结尾的最大子串的和，用d[]来存储该和，然后遍历一次即可，注意用max值来保存所需，不断更新max值

做完之后发现其实没必要用一个数组保存所有的和，直接用另一个变量保存前一个位置的最大和即可，代码是用list保存的没有改进= =

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AC代码（Python）

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 __author__ = 'YE'

 class Solution(object):
     def maxSubArray(self, nums):
         """
         :type nums: List[int]
         :rtype: int
         """
         length = len(nums)
         if length == 0:
             return 0
         if length == 1:
             return nums[0]

         d = [0 for i in range(length)]

         d[0] = nums[0]
         max = d[0]

         for i in range(1, length):
             d[i] = nums[i] + d[i - 1] if (nums[i] + d[i - 1]) > nums[i] else nums[i]
             if d[i] > max:
                 max = d[i]

         return max

 s = Solution()
 nums = [-2,1,-3,4,-1,2,1,-5, 4]
 print(s.maxSubArray(nums))