Maximum Product Subarray

Dynamic Programming

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.

C++实现代码：

#include<iostream>
using namespace std;

class Solution {
public:
    int maxProduct(int A[], int n) {
        if(n==0)
            return 0;
        int maxPro[n];
        int minPro[n];
        minPro[0]=maxPro[0]=A[0];
        int i;
        for(i=1;i<n;i++)
        {
            maxPro[i]=max(A[i],max(maxPro[i-1]*A[i],minPro[i-1]*A[i]));
            minPro[i]=min(A[i],min(maxPro[i-1]*A[i],minPro[i-1]*A[i]));
        }
        int max=maxPro[0];
        for(i=0;i<n;i++)
        {
            if(max<maxPro[i])
                max=maxPro[i];
        }
        return max;
    }
};

int main()
{
    Solution s;
    int arr[10]={2,3,-2,4};
    cout<<s.maxProduct(arr,4)<<endl;
}

 改进：

int maxProduct(int A[], int n) {
        if(n==0)
            return 0;
        int maxPro;
        int minPro;
        minPro=maxPro=A[0];
        int Rmax=A[0];
        int i;
        for(i=1;i<n;i++)
        {
            int tmax=maxPro;
            int tmin=minPro;
            maxPro=max(A[i],max(tmax*A[i],tmin*A[i]));
            minPro=min(A[i],min(tmax*A[i],tmin*A[i]));
            Rmax=max(Rmax,maxPro);
        }
        return Rmax;
    }