0053: Maximum Subarray

Problem Statement

Given an integer array nums, find the subarray with the largest sum, and return its sum.

Example 1:

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

Example 2:

Input: nums = [1]
Output: 1
Explanation: The subarray [1] has the largest sum 1.

Example 3:

Input: nums = [5,4,-1,7,8]
Output: 23
Explanation: The subarray [5,4,-1,7,8] has the largest sum 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.

Code Solution

class Solution:
    def maxSubArray(self, arr):
        csum = 0
        cmax = max(arr)
        for ix, n in enumerate(arr):
            csum = csum + n
            cmax = max(cmax, csum)
            if csum < 0:
                csum = 0
        return cmax