# LeetCode : 0152. Maximum Product Subarray (array)
###### tags:`leetcode`

#include <bits/stdc++.h>
#include <iostream>
#include <vector>
#include <unordered_map>
using std::vector;
using std::unordered_map;
using namespace std;

class BaseVectorPrint {
    public:
        void BasePrint00(vector<int>& num) {
            for (size_t i = 0; i < num.size(); ++i) {
                cout << "[" <<num.at(i) << "]" << "; ";
            }
            cout << endl;
        }

        void BasePrint01(vector<int>& num) {
            for (size_t i = 0; i < num.size(); ++i) {
                cout << num[i] << "; ";
            }
            cout << endl;
        }

        void BasePrint02(vector<int>& num) {
            for (const auto &item : num) {
                cout << item << "; ";
            }
            cout << endl;
        }
        
        void TwoDimensionalPrint(vector<vector<int>> &num){
            for (int i = 0; i < num.size(); i++)
            {
                for (int j = 0; j < num[i].size(); j++)
                {
                    cout << "[" << num[i][j] << "]";
                }
                cout << endl;
            }
        }
};

class BaseSolution {
public:
    int maxProduct(vector<int>& nums) {
        int MaxProduct = INT_MIN;
        for(int i = 0; i<nums.size(); i++){
            int ProductTemp = 1;
            for (int j = 0; j < i ; j++){
                ProductTemp *= nums[j];
                MaxProduct = max(MaxProduct,ProductTemp);
            }
        }
        return MaxProduct;
    }
//time complexity O(N^2) two for loop
//space complexity O(1)
};

class Solution01 {
public:
    int maxProduct(vector<int>& nums) {
        // Product quotient , defalut set first nums better 1;
        // plus , sub , defalut set first nums better 0;
        int Max = 1 ;
        int Min = 1 ;
        int MaxProd = INT_MIN;
        for (int i = 0 ; i < nums.size(); i++){
            int MaxTemp = Max * nums[i];
            int MinTemp = Min * nums[i];
            Max = max(nums[i],max(MaxTemp,MinTemp));
            // if 0 Product any nums = 0 , so nums[i] next new head
            // check Max Confirm the number, negative * negative = positive nums
            Min = min(nums[i],min(MaxTemp,MinTemp));
            // if 0 Product any nums = 0 , so nums[i] next new head
            // check Min Confirm the number, positive * positive = negative nums
            MaxProd = max(Max,MaxProd);
        }
        return MaxProd;
    }
//time complexity O(N) one for loop
//space complexity O(1)
};

int main(void)
{
    BaseVectorPrint printVector;
    Solution01 runfunc;

    vector<int> test01 = {  2,  3, -2,  4 };
    vector<int> test02 = { -2,  0, -1 };
    vector<int> test03 = { -1,  1,  0, -3,  3 };
    vector<int> ans ;
    int intAns;
    intAns = runfunc.maxProduct(test01);
    //printVector.BasePrint00(ans);

    printf("%d\n",intAns);
    printf("test\n");
    system("pause");
}

> Tip check if 0
> Tip check Max Confirm the number, negative * negative = positive
> Tip check Min Confirm the number, positive * positive = negative