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From: usenet@cps3xx.UUCP (Usenet file owner)
Newsgroups: comp.sources.wanted,alt.msdos.programmer
Subject: Need algorithm to scramble order of array
Message-ID: <3008@cps3xx.UUCP>
Date: 17 May 89 13:55:19 GMT
Reply-To: reedp@frith.egr.msu.edu ()
Organization: Michigan State University, Engineering, E. Lansing
Lines: 23

I need a fast algorithm to randomly rearrange the order of elements in
an array.  Right now I am just using a random number generator to form 
a list of numbers that directly determines the order of the array like this:

	n = size of array

	for i = 1 to n
		{
		do
			x = random number between 1 and n
		while x is not already in list[]

		list[i] = x
		}

The problem is that as the list fills up with numbers, the time spent in
the do loop getting a number not already in the list grows very large.

Does anyone know of a better way to do this?  Any help would be greatly 
appreciated!

Paul Reed
Internet: reedp@horus.cem.msu.edu               Bitnet:   reedp@MSUCEM