[leetcode] 53. Maximum Subarray

题目

Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.

A subarray is a contiguous part of an array.

Example 1:

Input: nums = [-2,1,-3,4,-1,2,1,-5,4]
Output: 6
Explanation: [4,-1,2,1] has the largest sum = 6.

Example 2:

Input: nums = [1]
Output: 1

Example 3:

Input: nums = [5,4,-1,7,8]
Output: 23

Constraints:

• 1 <= nums.length <= 105
• -104 <= nums[i] <= 104

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.

思路

贪婪算法

进阶：归并算法，待实现

代码

python版本：

class Solution:
    def maxSubArray(self, nums: List[int]) -> int:
        maxn, res = 0, -math.inf
        for num in nums:
            maxn += num
            res = max(res, maxn)
            if maxn < 0:
                maxn = 0
        return res

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