stack operation in recursive function

[Manjiri]

Hello everybody...


I want to know stack operation for recurssive factorilal function..... Means how it exactly returns value and over all calcultion will be carried out...U can follow the below code and explain...

#include<stdio.h>
int fact(int);
int main()
{
int f,n;
printf("Enter the number whose factorial you want to find..\n");
scanf("%d",&n);
f=fact(n);
printf("Factorial of given number is %d\n",f);
return 0;
}
 
int fact(int n)
{
int f;
if(n==0)
return(1);
else
return(fact(n-1)*n);
}

.Plz let me know...

Thank you,
Manjiri

[Ganon11]

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

Suppose the user enters 1. Then the function will enter once and hit the 'else' statement. Now we are finding fact(0) and multiplying it by 1 - in other words, returning simply fact(0). The function is entered again, and this time the 'if' branch is executed - 1 is returned. So fact(1) = fact(0) * 1 = 1 * 1 = 1.

Suppose the user enters 2. Then the function will enter and hit the 'else' statement. You are now finding fact(1) and multiplying it by 2. fact(1) evaluates in the same way as before, so fact(2) = fact(1) * 2 = (fact(0) * 1) * 2 = (1 * 1) * 2 = 2.

This can be generalized to:

fact(n) results in fact(n-1) * n = ((fact(n - 2) * (n - 1)) * n = ... = (((1 * 1) * 2) * 3)... * n.

The function will be executed n + 1 times.