product-array-puzzle.cpp

//{ Driver Code Starts
//Initial template for C++

#include<bits/stdc++.h>
using namespace std;



// } Driver Code Ends
//User function template for C++

class Solution{
  public:
    // nums: given vector
    // return the Product vector P that hold product except self at each index
    vector<long long int> productExceptSelf(vector<long long int>& nums, int n) {
        vector<long long> res;
        long long pdt = 1;
        for (auto i = nums.begin(); i != nums.end(); i++) {
            res.push_back(pdt);
            pdt *= *i;
        }
        pdt = 1;
        for (auto i = nums.rbegin(), j = res.rbegin(); i != nums.rend() && j != res.rend(); i++, j++) {
            *j *= pdt;
            pdt *= *i;
        }
        return res;
        //code here        
    }
};


//{ Driver Code Starts.
int main()
 {
    int t;  // number of test cases
    cin>>t;
    while(t--)
    {
        int n;  // size of the array
        cin>>n;
        vector<long long int> arr(n),vec(n);
        
        for(int i=0;i<n;i++)    // input the array
        {
            cin>>arr[i];
        }
        Solution obj;
        vec = obj.productExceptSelf(arr,n);   // function call
        
        for(int i=0;i<n;i++)    // print the output
        {
            cout << vec[i] << " ";
        }
        cout<<endl;
    }
	return 0;
}
// } Driver Code Ends