Overview

 

Question

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?

click for answer

2783915460

Solutions

 

Ruby

 millionPermutation.rb https://raw.github.com/addamh/euler/master/024/millionPermutation.rb download
#!/usr/bin/env ruby

puts (0..9).to_a.permutation.to_a[999999].join("")
$ time ruby millionPermutation.rb
real	0m4.233s
user	0m4.023s
sys	0m0.203s