Credits: Challenge contributed by Max Demian.
You are given a number N and a string S. Print all of the possible ways to write a string of length N from the characters in string S, comma delimited in alphabetical order.
The first argument will be the path to the input filename containing the test data. Each line in this file is a separate test case. Each line is in the format: N,S i.e. a positive integer, followed by a string (comma separated). E.g.
1,aa 2,ab 3,pop
Print all of the possible ways to write a string of length N from the characters in string S comma delimited in alphabetical order, with no duplicates. E.g.
a aa,ab,ba,bb ooo,oop,opo,opp,poo,pop,ppo,ppp