NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c++-part1/8210

Text File | 1996-08-05 | 1.9 KB | 42 lines

Path: sun001.spd.dsccc.com!spd!jmccarty
From: [e-mail] (Mike McCarty)
Newsgroups: comp.lang.pascal.misc,comp.lang.c++,comp.lang.c,comp.lang.pascal.borland
Subject: Re: Tough FACTORIAL math problem...
Date: 15 Feb 1996 19:20:30 GMT
Organization: DSC Communications Corporation, Plano, Texas USA
Message-ID: <4g011u$[e-mail]>
References: <4fr8be$[e-mail]> <[e-mail]>
NNTP-Posting-Host: aplo139.spd.dsccc.com

In article <[e-mail]>, John Cleland  <[e-mail]> wrote:
)The Crow wrote:
)>
)> Here is what I am trying to do, I want to find the last NON-ZERO digit of a
)> given factorial.  For instance,
)>
)> 5! = 120
)>
)> so the last non-zero digit is 2.  I want to be able to do this up to 1000.
)> Problem is, no matter how huge of a data-type you use, there isn't any way for
)> the computer to handle 1000!, it is however possible to find the last non-zero
)> digit somehow.  One thing I have tried is as I went through mulitplying the
)> series of numbers in the factorial (5 * 4 * 3 * 2) I would remove all the
)> trailing ZEROS, I got this to work up to 789, but it wont work with 1000 and i
)> am not really sure why.  If anyone has a clue how I can do this let me know.
)
)Don't just strip the trailing zeros, remove all digits except the last non-zero
)digit (which is your output) and then multiply by the next number in your sequence.
)This keeps the numbers down to a managable level and gives the correct answer as
)no more significant digit can affect the value of the LSD.

Per my previous reply: Perhaps I didn't go far enough. Keeping the 2 in
5! etc. works up to a point, after which the problem begins to show up
later in the game. Eventually you need to keep three, then four digits,
etc.

Mike
----
char *p="char *p=%c%s%c;main(){printf(p,34,p,34);}";main(){printf(p,34,p,34);}

I don't speak for DSC.         <- They make me say that.