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Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!uwvax!dogie.macc.wisc.edu!indri!polyslo!csun!csuna!abcscnge
From: abcscnge@csuna.csun.edu (Scott "The Pseudo-Hacker" Neugroschl)
Newsgroups: comp.sources.wanted,alt.msdos.programmer
Subject: Re: Need algorithm to scramble order of array
Message-ID: <1975@csuna.csun.edu>
Date: 18 May 89 06:50:03 GMT
References: <3008@cps3xx.UUCP>
Reply-To: abcscnge@csuna.csun.edu (Scott Neugroschl)
Organization: CSU Northridge
Lines: 30

In article <3008@cps3xx.UUCP> reedp@frith.egr.msu.edu () writes:
]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
]		}
]

list = array
N = size of list

for i from N down to 2 do
	x = random number between 1 and i inclusive
	swap list[i] and list[x]
end for

-- 
Scott "The Pseudo-Hacker" Neugroschl
UUCP:  ...!sm.unisys.com!csun!csuna.csun.edu!abcscnge
-- Beat me, Whip me, make me code in Ada
-- Disclaimers?  We don't need no stinking disclaimers!!!