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        riddles >> cs >> Fibonacci Serious in reverse Order 
        
(Message started by: tuxilogy on Jun 10^th, 2006, 3:41am)

Title: Fibonacci Serious in reverse Order
Post by tuxilogy on Jun 10^th, 2006, 3:41am

Hi can any one suggest me the algo regarding "Printing of the Fibonacci in reverse order "
Thanks in advance
TUX

Title: Re: Fibonacci Serious in reverse Order
Post by Barukh on Jun 10^th, 2006, 6:04am

What do you mean by "in reverse order"? Is a maximal element of the sequence given?

Title: Re: Fibonacci Serious in reverse Order
Post by tuxilogy on Jun 10^th, 2006, 6:49am

1,1,2,3,5 is the Fibbonacci series for n = 5,

reverse means given a number say n, one has to print

the series in thsi was ----> " 5, 3, 2, 1,1"..

Tux

Title: Re: Fibonacci Serious in reverse Order
Post by towr on Jun 10^th, 2006, 9:40am

I'd use recurrence

calculate the Kth fibonacci number (ideally, given the (K-1)th and (K-2)th ), call the function again for K+1 if K<N, print the Kth number.

But of course you could also use a stack.

Title: Re: Fibonacci Serious in reverse Order
Post by Grimbal on Jun 11^th, 2006, 1:19pm

Recurence?? Stack?? Surely you're joking, Mr. Towr!

void fiborev(int n){
int a=0, b=1;
while( n-->0 ) a = (b+=a)-a;
while( a ) printf(a?"%d,":"%d\n", b -= (a=b-a));
}

Title: Re: Fibonacci Serious in reverse Order
Post by towr on Jun 12^th, 2006, 12:55am

Well sure, you could also do that, if you want to calculate each value twice...

Recurrence and stacks is a more general way to print things in reverse though.. So that's why it was the first thing that came to mind.
You should see me print 1 to N in reverse ;)

Title: Re: Fibonacci Serious in reverse Order
Post by Grimbal on Jun 12^th, 2006, 1:56am

on 06/12/06 at 00:55:52, towr wrote:

Well sure, you could also do that, if you want to calculate each value twice...

4 times actually. I fixed that below. Should be 4 times faster.

fiborev(int n){
while( n-- )
printf(n?"%.0lf,":"%.0lf\n", exp(log((sqrt(5)+1)/2)*(n+1))/sqrt(5));
}

on 06/12/06 at 00:55:52, towr wrote:

You should see me print 1 to N in reverse ;)

There are 2 schools:
printf("N ot 1\n");
and
printf("1 to N in reverse\n");

Title: Re: Fibonacci Serious in reverse Order
Post by towr on Jun 12^th, 2006, 2:24am

on 06/12/06 at 01:56:39, Grimbal wrote:

There are 2 schools:
printf("N ot 1\n");
and
printf("1 to N in reverse\n");

Just two?
Why not
printf("reve1 to Nrse\n");
?

Title: Re: Fibonacci Serious in reverse Order
Post by Grimbal on Jun 12^th, 2006, 2:49am

Absolutely, a classical school. How could I have missed that one? ;D