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# factorial using recursion

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

int main()
{
int i=1,fact=1,n;
printf("enter the no of fact: ");
scanf("%d",&n);
factorial(n,fact,i);
return 0;
}
int factorial(int x,int y,int z)
{
int r;
if(x==1)
{
r=y*z;
printf("the fact is %d",r);
}
else
{

factorial(x--,y*z,z++);
}

}
``````

hello iam trying recursion using factorial the complier stops working .i dont understand why compiler does that

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rithish
Posting Whiz in Training
268 posts since Apr 2011
Reputation Points: 23
Skill Endorsements: 0

factorial(x--,y*z,z++);

You're passing the current value of x to factorial(), recursion never stops and you experience a stack overflow.

deceptikon
Challenge Accepted
3,428 posts since Jan 2012
Reputation Points: 822
Skill Endorsements: 56

Also you need to forward-declare your factorial function or define it before the main function.

sepp2k
Posting Whiz in Training
227 posts since Jul 2012
Reputation Points: 62
Skill Endorsements: 8

In addition to what Deceiptikon and sepp2k said, I would add that it yu've declared the function as returning an `int` value, but at no point to you actually return one.

There is actually a much simpler way to do this, one which takes only the starting value as an argument and returns it's factorial. If you think through the definition of a factorial, it is

``````N! = N * (N-1)!
``````

which could, as an example, be expanded to get

``````N! = N * (N - 1) * (N - 2)!
N! = N * (N - 1) * (N - 2) * (N - 3)!
N! = N * (N - 1) * (N - 2) * (N - 3) * (N - 4)!
``````

and so forth, eventually giving

``````N! = N * (N - 1) * ... 1
``````

meaning that all you need to do to calculate N! is to first calculate (N - 1)!, then multiply that by N. From this, the answer should be straightforward: just re-write the definition into C code.

``````int factorial(int x)
{
if (x <= 1)
return 1;
else
return ???   // insert factorial definition here, in C code
}
``````

This should be very easy to understand and implement; I've given you more than enough, too much very likely, and will leave the remaining half a line of code to you.

Schol-R-LEA
Veteran Poster
1,022 posts since Oct 2010
Reputation Points: 414