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Factorial program prints twice

dziugys1 (5)
Got this problem that program i've got here prints out answer twice.
If i'd explain its something like..
You input 3 and it will print out 
Factorial 1
Factorial 2
Factorial 6
Factorial 1
Factorial 2
Factorial 6
Factorial of 3 is 6


Program itself. 

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#include <stdio.h>

int fact (int num)
{
	
	int f;
	if(num == 0 || num == 1)
		f = 1;
	else
		f = num * fact(num-1);
		printf("Factorial %i \n", f);
	return f;
}

int main()
{
	
	int n;
	printf("Enter a positive integer: ");
	scanf("%i", &n);
	fact(n);
	printf("Factorial of %i is %i\n", n, fact(n));
	
	return 0;
}
Mantorr22 (152)
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#include <stdio.h>

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

int main()
{
	
	int n;
	printf("Enter a positive integer: ");
	scanf("%i", &n);
	fact(n);
	printf("Factorial of %i is %i\n", n, fact(n));
	
	return 0;
}


Enter a positive integer: 5
Factorial of 5 is 120


Why don't you try to delete the redundant output you don't need?
dziugys1 (5)
Yea makes sense really but initially i figured that i need to display all of it.

Write a program fact.c that asks the user to enter an integer number N.
 The program then prints out the first N factorial numbers.
 Remember that fac(1)=1, fac(n)=n*fac(n-1). 
You should use a function fac that is written recursively.
Last edited on
Mantorr22 (152)
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#include <stdio.h>

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

int main()
{
	
	int n;
	printf("Enter a positive integer: ");
	scanf("%i", &n);

	for(int i = 1; i <= n; i++)
	printf("Factorial of %i is %i\n", i, fact(i));
	
	return 0;
}


The program then prints out the first N factorial numbers.
Enter a positive integer: 10
Factorial of 1 is 1
Factorial of 2 is 2
Factorial of 3 is 6
Factorial of 4 is 24
Factorial of 5 is 120
Factorial of 6 is 720
Factorial of 7 is 5040
Factorial of 8 is 40320
Factorial of 9 is 362880
Factorial of 10 is 3628800
cire (8284)
ea makes sense really but initially i figured that i need to display all of it.

If the goal is to calculate a single factorial, then print outside of the function. If the goal is to display all of the factorials as they are recursively calculated, print inside the function. You may find you need to change the signature of the function if the latter is the case.
dziugys1 (5)
Yap was just attempting something like that however if i do for it comes up with
fact.c:20:2: error: ‘for’ loop initial declarations are only allowed in C99 mode

so not sure if i'm allowed additional flags while compiling. Not exactly a problem that it double prints but not exactly neat. However appreciate the help provided
Mantorr22 (152)
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#include <stdio.h>

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

int main()
{
	
	int n;
	printf("Enter a positive integer: ");
	scanf("%i", &n);

	int i; // <==
	for(i = 1; i <= n; i++)
	printf("Factorial of %i is %i\n", i, fact(i));
	
	return 0;
}


(?) You are using a very old compiler maybe? What is the compiler you are using?
dziugys1 (5)
Yea spec says nothing so ill just use -std=gnu99 to compile. Thanks a lot for the help!
mbozzi (3932)
So move the declaration out of the loop:

 
 
for(int i = 1; i <= n; i++)

Becomes:
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int i;
for(i = 1; i <= n; i++)
Last edited on
dziugys1 (5)
Linux KLIXX201WIN006W 4.2.0-27-generic #32~14.04.1-Ubuntu

It's uni's library PC and that's pretty much all around the campus.
Thanks for that little fix there.
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