10 replies to this topic

[kreol]

hey.. I have a simple program which calculates permutations of any given 2 long unsigned values

however, it runs.. and my factorial function works.. however, my permutation is not giving the correct output.. could somone please help me with this?

int factorial (unsigned long);
int permutation (unsigned long, unsigned long);
#include <iostream>
using namespace std;

int main()
{
	unsigned long n,r = 0;
cout << "please enter n value " << endl;
	cin >> n;
	cout << "please enter r value " << endl;
	cin >> r;
	cout << "P(" << n << "," << r << ") is equal to.." <<
	cout << permutation(n, r);
	

	return 0;
}

int factorial(unsigned long number) 
{
	int temp;

	if(number <= 1) return 1;

	temp = number * factorial(number - 1);
	return temp;
}

int permutation( unsigned long k, unsigned long r)
{
	int result = 0;
	int temp = k - r;

	result = factorial(k)/factorial(temp);
	return result;
}

Edited by WingedPanther, 18 April 2008 - 07:58 AM.
add code blocks

[WingedPanther]

Without seeing what your input/output is, it's hard to say. I can say, however, that even with "moderate" numbers, you will almost certainly find that an unsigned long int will have wrapped several times as you calculate your factorials.

[Xav]

I thought there were predefined factorial methods available already?

[kreol]

WingedPanther said:

Without seeing what your input/output is, it's hard to say. I can say, however, that even with "moderate" numbers, you will almost certainly find that an unsigned long int will have wrapped several times as you calculate your factorials.

I tried scaling everything back down to ints and I still recieve letters as an answer.

The inputs are small, such as 4,2 or 3,1

[WingedPanther]

You're getting LETTERS as part of your output??? That doesn't make sense. Can you list the specific output you are getting?

[kreol]

WingedPanther said:

You're getting LETTERS as part of your output??? That doesn't make sense. Can you list the specific output you are getting?

Input 1 = 4

Input 2 = 3



output = 6B254ACC1

[WingedPanther]

First, I would change your INTs to Unsigned Long.
Second, it appears that your output is in Hex.
Third, is there any reason you are using recursion?
Fourth, have you verified that your factorial function is producing correct results?

[kreol]

WingedPanther said:

First, I would change your INTs to Unsigned Long.
Second, it appears that your output is in Hex.
Third, is there any reason you are using recursion?
Fourth, have you verified that your factorial function is producing correct results?

1. just did.

2. its in hex and not even the correct result.

3. I did it for difficulty for my proj for more points instead of doing it plainly

4. yeah, I tested the factorial function, it works.

crap, only 50 minutes left

[kreol]

I fixed it.. it was a spacing problem that generated the error.. thanks though for pointing me into the direction of tweaking my code.. as I hardly ever do that lol

[Xav]

Great - it's always good to work out a problem yourself. Think of it as a challenge.

[WingedPanther]

It's the bugs like that that'll drive you nuts. It's almost has fun as getting rid of compiler errors (I saw a student have this sequence of error counts once):
400
300
150
30
2
700
The last error she fixed allowed the compiler to hit the REST of the code and start complaining all over. I had to work hard to get her to NOT undo her last change.