Question

Consider the following recursive definition of a factorial function.

int factorial ( int n)

{

   if ( n == 0 || n ==1 )

   return 1;

      else

   return n * factorial (n-1);

   }

Suppose the function factorial (4) is invoke. Trace through the function call, explicitly show how the factorial function is repeatedly called and what is the value of n in each call. Also show the value returned by each call.

Give an iterative implementation of the factorial function.

Answer 1

factorial (4) 
= 4 * factorial(3)
= 4 * 3 * factorial(2)
= 4 * 3 * 2 * factorial(1)
= 4 * 3 * 2 * 1
= 24

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Iterative version:
int factorial ( int n)
{
    int result = 1;
    for(int i = 1;i<=n;i++){
        result = result * i;
    }
    return result;
}