0053. Maximum Subarray

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.

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.

ac

class Solution {
    public int maxSubArray(int[] nums) {
        // edge case
        if (nums == null || nums.length == 0) return 0;

        int maxSum = Integer.MIN_VALUE, tmpSum = 0;
        for (int i = 0; i < nums.length; i++) {
            tmpSum += nums[i];
            maxSum = Math.max(maxSum, tmpSum);
            if (tmpSum < 0) tmpSum = 0;
        }

        return maxSum;
    }
}