leetcode：152. Maximum Product Subarray

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.

这是一道动态规划的题，状态转移方程为：
       Max[i]=max{a[i], Max[i-1]*a[i], Min[i-1]*a[i]};
       Min[i]=min{a[i], Max[i-1]*a[i], Min[i-1]*a[i]};

代码：

class Solution {public:    int maxProduct(vector<int>& nums) {        if(nums.size()==1)            return nums[0];        int res=nums[0];        int maxr[nums.size()],minr[nums.size()];        maxr[0]=nums[0];        minr[0]=nums[0];        for(int i=1;i<nums.size();i++){             maxr[i] = max(nums[i],  max(maxr[i-1] * nums[i], minr[i-1]*nums[i]));             minr[i] = min(nums[i],  min(minr[i-1] * nums[i], maxr[i-1]*nums[i]));             res=max(maxr[i],res);        }        return res;        }};