Thread: Factorial and Factorion, that is the question!

Well I thought I'd share this one with the group. It's the coolest thing I've had to try and solve. But anyway, I have the chance to earn to extra credit with this assignment.

assignment #1.

List all factorials from 1 to 100- something interesting happens?

assignment #2

A self-generating integer is such that the sum of the factorials of the digits of a number equal the number. For example:
1=1!=1*1=1
2=2!=2*1=2
145= 1!+4!+5!=1+24+120=145
There is one more. Create a program to find it.

For the first assignments, this is what I have so far.

Factorial:

public class Factorial
{
    // Evaluate n!
    public static long factorial( int n )
    {
        if( n <= 1 )     // base case
            return 1;
        else
            return n * factorial( n - 1 );
    }
 
    // Test program
    public static void main( String [ ] args )
    {
        for( int i = 1; i <= 100; i++ )
            System.out.println( factorial( i ) );
    }
}

Factorion:

import java.util.Scanner;
   public class Factorion {
      public static void main(String[] args) {
         int inputNumber;
         int number;
         int digit;
         int total;
         int factorial;
 
         Scanner keyboard = new Scanner(System.in);
 
         System.out.print("Please enter a positive integer (>=0):");
         inputNumber = keyboard.nextInt();
 
         while (inputNumber <= 0 || inputNumber == -0) {
            System.out.println("Sorry, the integer must be greater than or equal to 1.");
            System.out.print("Please enter a positive integer (>=0):");
            inputNumber = keyboard.nextInt();
         }
         total = 0;
         number = inputNumber;
         do {
            digit = number % 10;
 
            factorial = 1;
            for (int i = 1; i <= digit; i++) {
               factorial *= i;
            }
 
            total += factorial;
 
            number /= 10;
 
         } while (number > 0);
 
         if (total == inputNumber) {
            System.out.println(inputNumber + " is a factorion");
         }
         else {
            System.out.println(inputNumber + " is a not factorion");
         }
      }
   }

While this program works and does tell you if your number you entered is a factorion or not, I don't think it meets the prompt. I think what I should do here, is find a way to only print the 4 factorion numbers (boolean?) - 1, 2, 145, and 40585. The big part here is getting graded on the logic. I would think that if it's only printing out 4 numbers, it should at least be done with JOptionPane too.

Any thoughts on either of these?

Neil