DaniWeb Forum Index > Software Development > C

C RSS

Factorial program using an array.

Thread Solved

•

Join Date: Nov 2007

Posts: 7

Reputation: DennisB is an unknown quantity at this point

Solved Threads: 0

DennisB

Offline

Newbie Poster

Factorial program using an array.

Nov 8th, 2007

I am having problems trying to figure out exactly what is going wrong with my code. I am trying to create a factorial program using an array. I have tried, unsuccessfully, various ways to make it work but I can not figure it out. Any assistance would be appreciated.

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
#include <stdio.h>
 
int main(void)
{
	int iFac[10] = {0};
	int iTotal = 0;
	int iCount = 0;
	for (iCount = 0; iCount < 10; iCount++)
			iFac[iCount] = iCount;
			iTotal = (iCount * (iCount - 1)) * iCount;
	for (iCount = 0; iCount <= 10; iCount++)
			printf("\nThe value of the factorial is %d\n", iTotal);
	return 0;
}
#include <stdio.h>

int main(void)
{
	int iFac[10] = {0};
	int iTotal = 0;
	int iCount = 0;
	for (iCount = 0; iCount < 10; iCount++)
			iFac[iCount] = iCount;
			iTotal = (iCount * (iCount - 1)) * iCount;
	for (iCount = 0; iCount <= 10; iCount++)
			printf("\nThe value of the factorial is %d\n", iTotal);
	return 0;
}

Last edited by stymiee; Nov 8th, 2007 at 10:58 am. Reason: please use code tags

•

Join Date: Sep 2004

Posts: 7,603

Reputation: Narue has a reputation beyond repute

Solved Threads: 713

Narue

Offline

Code Goddess

Re: Factorial program using an array.

Nov 8th, 2007

You're storing the factorials in an array, but that doesn't change how you calculate the value. Do you know how to calculate a factorial?

I'm here to prove you wrong.

•

Join Date: Nov 2007

Posts: 7

Reputation: DennisB is an unknown quantity at this point

Solved Threads: 0

DennisB

Offline

Newbie Poster

Re: Factorial program using an array.

Nov 8th, 2007

Well, the math formula reads, for example:

5! = 1 x 2 x 3 x 4 x 5 = 120

•

Join Date: Sep 2004

Posts: 7,603

Reputation: Narue has a reputation beyond repute

Solved Threads: 713

Narue

Offline

Code Goddess

Re: Factorial program using an array.

Nov 8th, 2007

>Well, the math formula reads, for example:
Actually, it's more like: $n! = \displaystyle\prod_{k=1}^nk$ , but yours is close enough. However, knowing the formula doesn't mean you can write the code to implement it. Can you write a function that when given a value of n, produces the factorial of n? My point is that calculating n! is independent of what you do with the result. If you have a function that gives you n!, you can store it in an array just as easily as printing it:

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
int fac[10];
int i;
 
for ( i = 0; i < 10; i++ )
  fac[i] = factorial ( i );
 
for ( i = 0; i < 10; i++ )
  printf ( "%d\n", fac[i] );
int fac[10];
int i;

for ( i = 0; i < 10; i++ )
  fac[i] = factorial ( i );

for ( i = 0; i < 10; i++ )
  printf ( "%d\n", fac[i] );

I'm here to prove you wrong.

•

Join Date: Nov 2007

Posts: 7

Reputation: DennisB is an unknown quantity at this point

Solved Threads: 0

DennisB

Offline

Newbie Poster

Re: Factorial program using an array.

Nov 8th, 2007

So the factorial equation is what I should enter in the code where you have written the word factorial?

fac[i] = factorial ( i );

I am unsure of how to make the factorial n! into a math equation when using it for code.

•

Join Date: Sep 2004

Posts: 7,603

Reputation: Narue has a reputation beyond repute

Solved Threads: 713

Narue

Offline

Code Goddess

Re: Factorial program using an array.

Nov 8th, 2007

>what I should enter in the code where you have written the word factorial?
That's a function. You don't have to write a function, but you do have to loop from 1 to n and store the running product to calculate a factorial. Something like this is a translation of the formula into code:

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
int prod = 1;
int k = 1;
 
while ( k <= n )
  prod *= k;
int prod = 1;
int k = 1;

while ( k <= n )
  prod *= k;

I'm here to prove you wrong.

•

Join Date: Nov 2007

Posts: 7

Reputation: DennisB is an unknown quantity at this point

Solved Threads: 0

DennisB

Offline

Newbie Poster

Re: Factorial program using an array.

Nov 8th, 2007

OK, so the reference to factorial (i) is a declared function outside of main correct? In that declared factorial function is the loop you referenced to calculate the factorial? What does the operator *= mean? I am new at C so that's why I keep asking these questions.

•

Join Date: Sep 2004

Posts: 7,603

Reputation: Narue has a reputation beyond repute

Solved Threads: 713

Narue

Offline

Code Goddess

Re: Factorial program using an array.

Nov 8th, 2007

>What does the operator *= mean?
It means you should check your C reference. Not many people like to explain things that are easily discovered by looking in a book or searching google. In this case, *= means multiply and assign using the left hand operand as the left operand of the multiplication. It's functionally equivalent to this:

Help with Code Tags

C Syntax (Toggle Plain Text)

prod = prod * k;

I'm here to prove you wrong.

•

Join Date: Aug 2005

Posts: 5,264

Reputation: iamthwee is a splendid one to behold

Solved Threads: 377

iamthwee

Offline

Posting Expert

Re: Factorial program using an array.

Nov 8th, 2007

Draw a flow chart or write some pseudo code on paper first to help you visualise what is going on.

Last edited by iamthwee; Nov 8th, 2007 at 6:03 pm.

*Voted best profile in the world*

•

Join Date: Nov 2007

Posts: 7

Reputation: DennisB is an unknown quantity at this point

Solved Threads: 0

DennisB

Offline

Newbie Poster

Re: Factorial program using an array.

#10

Nov 9th, 2007

I do understand arrays, somewhat. I created a Fibonacci Sequence array and tried to apply the same thinking to the factorial program but could not figure it out.