[leetcode]Maximum Product Subarray

class Solution {
public:
//和最大子串和不同的是：需要同时记录最大的正数和最小的负数
int maxProduct(int A[], int n) {
if(n==0) return 0;
if(n==1) return A[0]; //这一句不能少，否则在就输出maxVal=0
int maxPosValEndsWithLast = 0;
int minNegValEndsWithLast = 0;
int maxVal=0;
int minVal=0;
for(int i=0;i<n;i++){
if(A[i]>0){
maxPosValEndsWithLast = max( maxPosValEndsWithLast*A[i], A[i]);
minNegValEndsWithLast = min( minNegValEndsWithLast*A[i], A[i]);
}else if(A[i]<0){
int temp = maxPosValEndsWithLast; //注意保存临时现场
maxPosValEndsWithLast = minNegValEndsWithLast*A[i];
minNegValEndsWithLast = min( temp*A[i], A[i]);
}else{//A[i]==0
maxPosValEndsWithLast = 0;
minNegValEndsWithLast = 0;
}

//update
maxVal = max(maxVal,maxPosValEndsWithLast);
minVal = min(minVal,minNegValEndsWithLast);
}
return maxVal;
}
};