53-maximum-subarray

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Description

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.

Solution(Python)

class Solution:
    def maxSubArray(self, nums: List[int]) -> int:
        max_sum = float("-inf")
        cur_sum = 0

        for num in nums:
            if cur_sum + num > num:
                cur_sum = cur_sum + num
            else:
                cur_sum = num

            if cur_sum > max_sum:
                max_sum = cur_sum

        return max_sum