LeetCode - Maximum Subarray

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.

如果当前的和小于0，则在后面的数加上现在的和只会比原来的数要小，故舍弃

DP的思路：

O(n)就是一维DP。
假设A(0, i)区间存在k，使得[k, i]区间是以i结尾区间的最大值，定义为Max[i]，当求取Max[i+1]时，

然后从左往右扫描，求取Max数字的最大值即为所求。

class Solution {
public:
    int maxSubArray(int A[], int n) {
        int ans = 0;
        int maxsum = INT_MIN;
        
        for (int i = 0; i < n; i++)
        {
            if (ans < 0)
                ans = 0;
            ans += A[i];
            maxsum = max(ans, maxsum);
        }
        return maxsum;
    }
};