سؤال حول Recursion

welcome...

Typically, there is no need to return 2 and of course it's wrong to do so, because this point must be the last point before the factorial function is being returned. Don't forget that n will be decreased and at sometime will be 1. And behind the scene it will do the last multiplication process.

It's the habit of the recursion process-- called by itself...

That is the reason for why you've always got 48 when you pass in 4 as a factorial number or any... Because 24 * 2 = 48... at sometime it will come back again to check for 1 that is true then doing the last call to itself...

Sorry I think so...

(n == 1) it returns 1, which equals n, so that it will multiple by the previous number (1 * 2 * 3....)

(n == 0) it returns 1, because it is just a rule

bye

Well!!

Okay, you have to believe that the first process of this is just CALLING functions not more. Ok? :happy:

Until the programm is reaching and getting within the body of the last called function.

In this example it is the last factorial(1)...at this time the condition is true then it will return 2 to the immediate previous caller and the progress will be continued backwards to the upper caller again and again and again...

Ok...

I've drawn the following picture to grasp the operation...

Yes indeed, there is no magic here...the above figure picture describes the mathematical fact of the factorial operation but programmatically.

The factorial is the product of all integer numbers from 1 up to a specified number...

For instance...the factorial of 4 (mathematically) is:

Yeah! so according to this! the number 1 has to be involved in the factorial process somehow and the innermost returned value must be 1.

Now! may you read the previous line(the example) from right to left and the previous figure picture from down to up to grasp this process clearly...

So for this math fact and this rule the returned value must be 1...

Sorry, I know that you know! but now the process is clear for which why it should be 1 instead of 2 or of any other number because the last|innermost multiplication operation has to be by 1.

bye...

1.  
2. /*
3. * Fonction recursive simple.
4. */
5. unsigned long factoriel (int n)
6. {
7.  
8. if (n == 1 || n == 0)
9. return 1;
10.  
11. return n * factoriel (n - 1);
12. }
13.