Permutations
Permutations - The Password Checker Program
From mathworld.wolfram.com:
"The number of permutations on a
set of 
elements is given by 
(
factorial;
Uspensky 1937, p. 18). For example, there are 
permutations of 
,
namely 
and 
,
and 
permutations of 
,
namely 
,
,
,
,
,
and 
."
elements is given by ( factorial;
Uspensky 1937, p. 18). For example, there are permutations of ,
namely
and ,
and permutations of ,
namely ,
,
,
,
,
and ."A permutation can be a rearrangement of letters in a word. For example, the permutations of 'log' are:
- log
- lgo
- glo
- gol
- ogl
- olg