Find the contiguous subarray within an array (containing at least one number) which has the largest sum.

For example, given the array [-2,1,-3,4,-1,2,1,-5,4],
the contiguous subarray [4,-1,2,1] has the largest sum = 6.

只要知道 除非全負，任何的負的子序列不可能是最優子序列的前綴 就可以了。

我的代碼：

class Solution {
public:
    int maxSubArray(vector<int
 
>& nums) {
        int max = nums[0], now = 0;
        for (int i = 0; i < nums.size(); i++) {
            now += nums[i];
            if (now >= max) max = now;
            if (now < 0) now = 0;
        }
        return max;
    }
};

[leetcode] 53. Maximum Subarray