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.

Example:

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

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.

解题要点：

遍历并存一个当前sum，在loop里判断sum的大小，是否留原sum还是重新开始算sum。储存最大sum，返回这个值。

class Solution {
    public int maxSubArray(int[] nums) {
        int sum = nums[0];
        int res = sum;
        for(int i = 1; i < nums.length; i++){
            sum = sum < 0 ? nums[i] : sum + nums[i];
            res = Math.max(res, sum);
        }
        return res;
    }
}