Recursively print Factorial values in decreasing order?

Question

Using C++ to figure out the factorial is straightforward enough. To print the values coming up (if factorial is 5) ... 1 * 2, * 3, * 4 * 5 also no problem - as I think I've done below. But what I'm having a hard time doing is saying show me 5 * 4 then value * 3 then value * 2 etc. I want to be able to print the data going down and I can't seem to figure it out.

#include <iostream>
using namespace std;   

int factorial(int n);

int main()
{
   int number;

   cout << "Enter an integer value ";
   cin >> number;

   cout << "The factorial of " << number << " is ";
   cout << factorial(number) << endl;
}

int factorial(int n)
{
   if (n == 0)
      return 1;                    // Base case
   else
   {
      n = n * factorial(n - 1); // Recursive case
      cout << " going up" << n << " ";
      return n;
   }
}

There are a couple of other posts but I didn't find one asking the same thing. The desired results are: 20 60 120 The current results are 1 2 6 24 120 Please advise. Thank you.

Answer 1

Just change where you are printing the value

else
   {
      n = n * factorial(n - 1); // Recursive case
      cout << " going up" << n << " ";
      return n;
   }

to

else
   {
      cout << " going down" << n << " ";    
      n = n * factorial(n - 1); // Recursive case
      return n;
   }

The above would print 5 4 3 2 1 but if you want something like

5 20 60 ...

Than you have to change the recursive definition a bit.

#include<iostream>

using namespace std;
int factorial(int n,int temp);
int main()
{
   int number;

   cout << "Enter an integer value ";
   cin >> number;

   cout << "The factorial of " << number << " is ";
   cout << factorial(number,1) << endl;
}

int factorial(int n,int temp)
{
   if (n == 0)
      return temp;                    // Base case
   else
   {   
      cout << " going down" << n * temp << " ";
      factorial(n - 1,n*temp); // Recursive case
      //return n;
   }   
}