MDTKINDIA What is a recursive function? 1

[Spannerman]

Thanks for your reply MDTKINDIA what is a recursive function????

 

[mbaranski]

OK, you have to think about this:

let's think about n factorial, or n!:

1. Define a base case, or for our example:

if n = 0, n! = 1;

2. Define a recursive case:
if n > 0, n! = n * (n - 1)!
or, n factorial equals n times n-1 factorial

Think about this, we'll do an example:

take 4, 4!, using our recursive steps, is:
4! = 4 * 3!
4 * 3! = 4 * 3 * 2!
4 * 3 * 2! = 4 * 3 * 2 * 1!
4 * 3 * 2 * 1! = 4 * 3 * 2 * 1 * 0!
and, since 0! = 1, we have
4 * 3 * 2 * 1 * 1, or 4 * 3 * 2 * 1, which is the definition of factorial. In c, you would write this as:

int factorial (int n){
if (n == 0)
return 1;
else
return (n * factorial(n-1));
}

This will use the stack, and call itself until we reach the base case. The base case is very important, you must ensure that you will reach the base case. In the previous example, I know we won't be stuck in an infinite loop because each time we call the function we are decrementing n.

Good Luck, and if you need any more help, just post. I'm also putting this in the faq section. As always, I hope that helped!

Disclaimer:
Beware: Studies have shown that research causes cancer in lab rats.