Lexicographic permutations

gistfile1.rb

# Project Euler: Problem 24
# Lexicographic permutations
# https://projecteuler.net/problem=24

def fact(x); (1..x).reduce(1,:*); end

l=(0..9).to_a
out = []
marker = 1_000_000
while !l.empty? do
  puts marker
  m,ind = l.each_with_index.find{ |x,i| (i+1) * fact(9-out.size) >= marker }
  marker -= ind * fact(9-out.size)
  out << l.delete(m)
end
out