53. Maximum Subarray

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.

---

Solution1:

class Solution:
    # @param A, a list of integers
    # @return an integer
    # 6:57
    def maxSubArray(self, A):
        if not A:
            return 0

        curSum = maxSum = A[0]
        for num in A[1:]:
            curSum = max(num, curSum + num)
            maxSum = max(maxSum, curSum)

        return maxSum

Analyze: