class Solution {
public:
    vector<int> productExceptSelf(vector<int>& nums) {
        
        int n=nums.size();
        int left=1,right=1;     //left：从左边累乘，right：从右边累乘
        vector<int> res(n,1);
        
        for(int i=0;i<n;++i)    //最终每个元素其左右乘积进行相乘得出结果
        {
            res[i]*=left;       //乘以其左边的乘积
            left*=nums[i];
            
            res[n-1-i]*=right;  //乘以其右边的乘积
            right*=nums[n-1-i];
        }
        
        return res;
        
    }
};

class Solution {
public:
    vector<int> productExceptSelf(vector<int>& nums) {
        vector<int>temp_1(nums.size()+2);
        vector<int>temp_2(nums.size()+2);
        vector<int>result(nums.size());
        int n = nums.size()-1;
        for(int i=0;i<temp_1.size();i++){
            temp_1[i]++;
            temp_2[i]++;
        }
        for(int i=0;i<nums.size();i++){
            temp_1[i+1] = temp_1[i]*nums[i];
            temp_2[n-i+1] = temp_2[n-i+2]*nums[n-i];
        }
        for(int i=0;i<=n;i++){
            result[i] = temp_2[i+2]*temp_1[i];
        }
        return result;
    }
};