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

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

这和Maximum Subarray有些类似，Maximum Subarray求的是最大和，这里求的是连续子数组的最大乘积

考虑到整数和负数，用currentmax表示包含到当前A[i]节点的最大乘积，currentmin表示包含到当前节点A[i]的最小乘积，即乘积的最小值。

res记录遍历过程中最大的结果

class Solution {
public:
    #define MAX(a,b,c)  (((a>b)?a:b)>c)?((a>b)?a:b):c
    #define MIN(a,b,c)  (((a<b)?a:b)<c)?((a<b)?a:b):c
    int maxProduct(int A[], int n) {
        //currentmax=MAX{A[i],currentmax*A[i],currentmin*A[i]}
        //currentmin=MIN{A[i],currentmax*A[i],currentmin*A[i]}
        //res=MAX{res,currentmax，currentmin}
        
        int currentmax;
        int currentmin;
        int res;
        if(n<=0)
            return 0;
        if(n==1)
            return A[0];
        
        currentmax=currentmin=res=A[0];
        for(int i=1;i<n;i++)
        {
            int temp1=currentmax*A[i];
			int temp2=currentmin*A[i];
			currentmax=MAX(A[i],temp1,temp2);
			currentmin=MIN(A[i],temp1,temp2);

			//res=(((currentmax>currentmin)?currentmax:currentmin)>res)?((currentmax>currentmin)?currentmax:currentmin):res;
			res=MAX(res,currentmax,currentmin);

        }
        
        return res;
    }
};