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.

DP，一个变量记录最大值，一个变量记录当前的和

public class Solution {
    //Time: O(n)  Space: O(1)
    public int maxSubArray(int[] A) {
        if (A == null || A.length == 0) {
            return 0;
        }
        int sum = 0;
        int max = Integer.MIN_VALUE;
        for (int i = 0; i < A.length; i++) {
            sum += A[i];
            max = Math.max(max, sum);
            sum = Math.max(0, sum);
        }
        return max;
    }
}