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Index › Programming Questions & Help › Syntax Questions › Random permutations
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Random permutations (Read 841 times)
BrianV
Random permutations
Jan 13th, 2009, 10:42pm  
Hello,

I'm new to Processing and want to randomly permute a large array of integers.  Is there such a function in Processing (ie: the opposite of the array function sort() ) or does someone know of an efficient algorithm?

Thanks.
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sw01
Re: Random permutations
Reply #1 - Jan 13th, 2009, 11:08pm  
Shuffle is built into Java:

Code:

import java.util.Collections;

ArrayList a = new ArrayList();

a.add("A");
a.add("B");
a.add("C");

for(int i = 0; i < a.size(); i++){
  print((String)a.get(i));
}


println("");

java.util.Collections.shuffle(a);

for(int i = 0; i < a.size(); i++){
  print((String)a.get(i));
}


println("");

java.util.Collections.shuffle(a);

for(int i = 0; i < a.size(); i++){
  print((String)a.get(i));
}


Handy, no? Smiley

source:
http://java.sun.com/j2se/1.4.2/docs/api/java/util/Collections.html
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BrianV
Re: Random permutations
Reply #2 - Jan 14th, 2009, 12:15am  
Thanks a lot.  It seems that did the trick.  Never in a million years would I have found (or even recognized had I found) that Java utility.

You've also shown me that had I searched for 'shuffle' instead of 'permutation' I would have found the answer in previous posts.
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sw01
Re: Random permutations
Reply #3 - Jan 14th, 2009, 12:56am  
You're welcome.  I'm also guilty of not looking it up Smiley
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