等差数列

hena11pre.rb

#!/usr/bin/env ruby
#http://qiita.com/items/c206fbc645c255cb7de6
#http://nabetani.sakura.ne.jp/hena/ord11arithseq/
STDOUT.sync=true
while gets
    h={}
    $_.chomp.chars{|e|h[e.to_i(36)]=1} # because already sorted...
    r=1
    0.step(35){|i|
        if h.has_key?(i)
            1.step(35){|j|
                k=1
                while h.has_key?(i+j*k) do k+=1 end
                r=[r,k].max
            }
        end
    }
    p r
end