=begin

A permutation is an ordered arrangement of objects. For example, 3124 is one possible permutation of the digits 1, 2, 3 and 4. If all of the permutations are listed numerically or alphabetically, we call it lexicographic order. The lexicographic permutations of 0, 1 and 2 are:

012   021   102   120   201   210

What is the millionth lexicographic permutation of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9?

=end

nums = %w(0 1 2 3 4 5 6 7 8 9)
@perms = []
@i = 0

def permutations(nums,str)
  if nums.length == 0
    @i += 1
    if @i == 1000000
      print str
    end
  else
    nums.each do |n|
        thesenums = nums.clone
        thesenums.delete(n)
        permutations(thesenums,str+n)
    end
  end
end

permutations(nums,'')