Little Red Book » Factorial

Chapter 3 - Question 1

Using a small input integer, N say, compute and print factorial N.

Solution 1

C++:

#include <stdio.h>
#include <stdlib.h>

using namespace std;

int main(int argc, char **argv)
{
int n = atoi(argv[1]);
int total = 1;

for (int a = 1; a <= n; a++)
total *= a;

printf("The factorial of %d is %d.", n, total);
}

Example use:

C:\code>factorial 4
The factorial of 4 is 24.
C:\code>

Solution 2

VB:

Warning: Unexpected character in input: ''' (ASCII=39) state=1 in /home/icey/public_html/code/php_highlight.php on line 169
Sub main()

' this holds the factorial
Dim lngTotal As Long
' this will be the number entered by the user
Dim n As Integer

' ensure random numbers are random
Randomize

' get something from the user and convert it into an integer
n = Val(InputBox("Enter a small integer", "Factorial", Int(10 * Rnd) + 1))

' check they entered a positive number
If (n > 0) Then
' start at 1
lngTotal = 1
' loop up to the user entered number
For a = 1 To n
' multiply by each number
lngTotal = lngTotal * a
Next
show the original number and its factorial
MsgBox "The factorial of " & n & " is " & lngTotal & ".", vbInformation, "Factorial"
End If

End Sub

The colours are set up for PHP/C++ so they will look a bit strange.

Solution 3

PHP:

<?
// generate a random integer
$n = intval(mt_rand(1, 10));
// start the total at one
$total = 1;

// loop from 1 to the specified number
for ($a = 1; $a <= $n; $a++)
// multiply the total by this amount
$total *= $a;

// show the original number and the factorial
echo 'The factorial of ' . $n . ' is ' . $total;
?>

Which produces:

The factorial of 3 is 6

Solution 4

Javascript:

<script language="javascript">

</script>

Log

May 1, 2005 - Added solution 1, 2, 3 and 4.