From owner-freebsd-questions  Sat Nov 25 14:38:43 2000
Delivered-To: freebsd-questions@freebsd.org
Received: from mailhost01.reflexnet.net (mailhost01.reflexnet.net [64.6.192.82])
	by hub.freebsd.org (Postfix) with ESMTP id 12EF837B4F9
	for <freebsd-questions@freebsd.org>; Sat, 25 Nov 2000 14:38:39 -0800 (PST)
Received: from 149.211.6.64.reflexcom.com ([64.6.211.149]) by mailhost01.reflexnet.net  with Microsoft SMTPSVC(5.5.1877.197.19);
	 Sat, 25 Nov 2000 14:37:09 -0800
Received: (from cjc@localhost)
	by 149.211.6.64.reflexcom.com (8.11.0/8.11.0) id eAPMcc196273;
	Sat, 25 Nov 2000 14:38:38 -0800 (PST)
	(envelope-from cjc)
Date: Sat, 25 Nov 2000 14:38:38 -0800
From: "Crist J . Clark" <cjclark@reflexnet.net>
To: Sue Blake <sue@welearn.com.au>
Cc: freebsd-questions@FreeBSD.ORG
Subject: Re: unsorting
Message-ID: <20001125143838.Z12190@149.211.6.64.reflexcom.com>
Reply-To: cjclark@alum.mit.edu
References: <20001126023150.F377@welearn.com.au>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
X-Mailer: Mutt 1.0i
In-Reply-To: <20001126023150.F377@welearn.com.au>; from sue@welearn.com.au on Sun, Nov 26, 2000 at 02:31:53AM +1100
Sender: owner-freebsd-questions@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.ORG

On Sun, Nov 26, 2000 at 02:31:53AM +1100, Sue Blake wrote:
> Is there some fairly simple way I can put a list of letters or words,
> or lines of a text file, into a random order?

That's called a shuffle, like shuffling a deck of cards. The classic
approach is Knuth's algorithm. There's a Perl module to do it if you
want to do a quick web search.

However, a really quick and ugly approach is to load the list into
memory, then just step through it swapping each item with another in a
random location. To be a little different, here is an awk(1) script
that does it,

  {
    line[NR] = $0;
  }

  END {
    for(i=1;i<=NR;i++) {
      pos = int(rand()*NR);
      line_hold = line[i];
      line[i]   = line[pos];
      line[pos] = line_hold;
    }
    for(i=1;i<=NR;i++) {
      print line[i];
    }
  }

That is not nearly the quickest or most graceful way, but it will
work. The incremental improvements to this method are left as an
excercise for the reader. ;)
-- 
Crist J. Clark                           cjclark@alum.mit.edu


To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-questions" in the body of the message