[python] LeetCode 53. Maximum Subarray

题目描述

原题链接地址：https://leetcode.com/problems/maximum-subarray/description/
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.

思路

动态规划：res[i] = max(res[i-1]+nums[i], nums[i])

代码

class Solution:
    def maxSubArray(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        if len(nums)<=1:
            return max(nums)
        self.res = [None for _ in range(len(nums))]
        self.dp(nums, len(nums)-1)
        return max(self.res)
    
    def dp(self, nums, index):
        if index == 0:
            self.res[index] = nums[0]
            return 
        self.dp(nums, index-1)
        self.res[index] = max(self.res[index-1]+nums[index], nums[index])