leetcode - 53. Maximum Subarray

topic

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.

Follow up:

If you have figured out the O(n) solution, try coding another solution using the divide and conquer approach, which is more subtle.

A thought:

Dynamic Programming. An array subscript to put the nums [i] array at the end of the maximum value of i is a lattice. 

    def maxSubArray(self, nums: List[int]) -> int:
        dp = [0]*len(nums)
        # 以nums[i]结尾的最大子序列的值
        dp[0] = nums[0]
        for i in range(1,len(nums)):
            if dp[i-1] < 0:
                dp[i] = nums[i]
            else:
                dp[i] = dp[i-1] + nums[i]
        return max(dp)

Thinking two:

As long as the number in front of the plus and> 0, you can always add down. But <0 that this section would not take it.

    def maxSubArray(self, nums: List[int]) -> int:
        for i in range(1,len(nums)):
            if nums[i-1]>0:
                nums[i] += nums[i-1]
        return max(nums)

This approach is seen in the analysis in, really amazing

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Origin blog.csdn.net/qq_22498427/article/details/105101747