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Permutations - The Password Checker Program
From mathworld.wolfram.com:
"The number of permutations on a
set of ![n](http://mathworld.wolfram.com/images/equations/Permutation/inline3.gif)
elements is given by ![n!](http://mathworld.wolfram.com/images/equations/Permutation/inline4.gif) ( factorial;
Uspensky 1937, p. 18). For example, there are ![2!==2.1==2](http://mathworld.wolfram.com/images/equations/Permutation/inline6.gif) permutations of ![{1,2}](http://mathworld.wolfram.com/images/equations/Permutation/inline7.gif) ,
namely ![{1,2}](http://mathworld.wolfram.com/images/equations/Permutation/inline8.gif)
and ![{2,1}](http://mathworld.wolfram.com/images/equations/Permutation/inline9.gif) ,
and ![3!==3.2.1==6](http://mathworld.wolfram.com/images/equations/Permutation/inline10.gif) permutations of ![{1,2,3}](http://mathworld.wolfram.com/images/equations/Permutation/inline11.gif) ,
namely ![{1,2,3}](http://mathworld.wolfram.com/images/equations/Permutation/inline12.gif) ,
![{1,3,2}](http://mathworld.wolfram.com/images/equations/Permutation/inline13.gif) ,
![{2,1,3}](http://mathworld.wolfram.com/images/equations/Permutation/inline14.gif) ,
![{2,3,1}](http://mathworld.wolfram.com/images/equations/Permutation/inline15.gif) ,
![{3,1,2}](http://mathworld.wolfram.com/images/equations/Permutation/inline16.gif) ,
and ![{3,2,1}](http://mathworld.wolfram.com/images/equations/Permutation/inline17.gif) ."
A permutation can be a rearrangement of letters in a word. For
example, the permutations of 'log' are:
Box Trace
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