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macOS C++; fibonacci and GCF.

F

fBaran

macrumors regular
Original poster
Oct 22, 2003
218
0
Here is my fib() function:

Code: 
int fib (int x)
    { int i, count=0;
                if (x==1 || x==2) return 1;
        for (i=0; i < x; i++)
            {
                count = (x-1) + (x-2);
            }
        return count;   
    }
I've been working on this for a couple of hours now, but I can't get it correctly calculate the numbers. A little help?

Thank you all for your input ::cue rimshot:: !
 
gammamonk

gammamonk

macrumors 6502a
Jun 4, 2004
666
105
Madison, WI
Are you allowed to use recursion? I'm assuming this is for a class or something.

Here's some code I found in 6 seconds on google.

//
// This file contains the C++ code from Program 3.4 of
// "Data Structures and Algorithms
// with Object-Oriented Design Patterns in C++"
// by Bruno R. Preiss.
//
// Copyright (c) 1998 by Bruno R. Preiss, P.Eng. All rights reserved.
//
// http://www.pads.uwaterloo.ca/Bruno.Preiss/books/opus4/programs/pgm03_04.cpp
//
unsigned int Fibonacci (unsigned int n)
{
if (n == 0 || n == 1)
return n;
else
return Fibonacci (n - 1U) + Fibonacci (n - 2U);
}
Click to expand...
 
F

fBaran

macrumors regular
Original poster
Oct 22, 2003
218
0
My bad. I should have specified NO recursion (that would be too easy). The old fashion iteration!
 
HexMonkey

HexMonkey

Administrator emeritus
Feb 5, 2004
2,240
504
New Zealand
Try this:

Code: 
int fib (int x)
{
	//For the first two terms, return 1
	if (x==1 || x==2) return 1;
	
	int i, prev2=1, prev=1, newTerm;
	for (i=2; i<x; i++)
	{
		//Find the next term
		newTerm = prev + prev2;
		//Update the last two terms
		prev2 = prev;
		prev = newTerm;
	}
	return newTerm;
}
 
F

fBaran

macrumors regular
Original poster
Oct 22, 2003
218
0
g0gie said:
Cheater!!! do it and learn it!!! A CS degree is coveted!!!
Click to expand...
If you're not going to contribute to my thread, don't post it in.
-------

Thanks a lot HexMonkey, I think what I did wrong is that I didn't sawp anything, so thing just kept getting overwritten. Is that right? Clearly, I don't have any swaps, so it must've been recycling old numbers.
 
NewbieNerd

NewbieNerd

macrumors 6502a
Sep 22, 2005
512
0
Chicago, IL
No, your program as it stands is just adding up numbers less than x twice for the most part. You are correct in returning 1 if x=1 or x=2, but from that step on you should keep track of variables like last and prev, which will be the last two fib numbers you have found so far.

So in the beginning, last = prev = 1. Then, for the remaining x-2 iterations, you need to make prev = last and last = prev + last (use a temp variable to help you do this). In the end, return last.
 
colocolo

colocolo

macrumors 6502
Jan 17, 2002
480
132
Santiago, Chile
g0gie said:
Cheater!!! do it and learn it!!! A CS degree is coveted!!!
Click to expand...

Edit: Sorry, on second thought my comments on how unappropiate this thread is because it is as morally wrong as piracy might be out of place.

I do not have enough information about the situation of the OT to judge him as doing something wrong by asking his homework to be done.

Maybe he really tried hard and has the will to learn after all.

If you happenned to read my post before I edited it, I apologize.
 
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