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Index › Programming Questions & Help › Programs › Randomizing the characters of a String
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Randomizing the characters of a String? (Read 273 times)
jsavage
Randomizing the characters of a String?
Dec 16th, 2008, 9:05pm  
I would like to take a String, such as "How Do You Do?" and randomize it so my output would be something like this: "oD?DYo H ou wo".  It would have to be the same output every time, (seeded).

What's the best way to handle this?  I think I'd be using some of the methods of the String class? but I'm not sure how to go about structuring this.
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koogy
Re: Randomizing the characters of a String?
Reply #1 - Dec 16th, 2008, 9:41pm  
knuth shuffle, O(n)

seed random generator
for each letter in the string
 pick a random letter anywhere* in the string
 swap them
the end

* can also be the same position leaving the letter in the same place.

use StringBuffer rather than String, allows you to insert letters mid-string. charAt(), setCharAt()

http://java.sun.com/j2se/1.5.0/docs/api/java/lang/StringBuffer.html
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koogy
Re: Randomizing the characters of a String?
Reply #2 - Dec 16th, 2008, 10:02pm  
oops

http://dev.netcetera.org/blog/2007/08/24/good-knuth-bad-knuth/

you should only pick letters from the currently unshuffled bit and, like he says, this is easier if you move backwards through the string.
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