开始动态规划啦！
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.

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