Maximum Subarray

Maximum Subarray

问题：

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.

思路：

　　不定长的滑动窗口，对于非负数对窗口有积极作用，对于负数，影响到窗口的正值了，窗口重新开始，没影响，窗口继续

我的代码：

public class Solution {
    public int maxSubArray(int[] A) {
        int max = Integer.MIN_VALUE;
        if(A == null || A.length == 0)  return max;
        int len = A.length;
        for(int i = 0; i < len; i++)
        {
            max = Math.max(A[i],max);
        }
        int curSum = 0;
        for(int i = 0; i < len; i++)
        {
            int cur = A[i];
            if( cur >= 0)
            {
                curSum += cur;
                max = Math.max(curSum,max);
            }
            else
            {
                if(curSum + cur < 0)    curSum = 0;
                else    curSum += cur;
            }
        }
        return max;
    }
}

别人代码：

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

        return max;
    }
}

学习之处：

　　别人的代码简介，但是不好理解

need to learn