William James wrote:
> Simon Kröçer wrote:
> > William James wrote:
> > > Short:
> > >
[ clipped ]
> >
> > Using Dominik's nice idea i boiled it down to:
> > (the dictionary is the optional third parameter, no -d)
> >
> > -----------------------------------------------------------
> > dict, len = Hash.new{|h,k|h[k] = []}, ARGV[0].size
> > IO.foreach(ARGV[2] || 'words.txt') do |w| w.chomp!
> >    if w.size != len then next else s = w.dup end
> >    (0...w.size).each{|i|s[i]=?.; dict[s] << w; s[i]=w[i]}
> > end
> > t, known = {ARGV[1] => 0}, {}
> > while !known.merge!(t).include?(ARGV[0])
> >    t = t.keys.inject({}){|h, w|(0...w.size).each{|i|
> >      s=w.dup; s[i]=?.; dict[s].each{|l|h[l] = w if !known[l]}};h}
> >    warn 'no way!' or exit if t.empty?
> > end
> > puts w = ARGV[0]; puts w while (w = known[w]) != 0
> > -----------------------------------------------------------
> >
> > It's still quite fast.
>
> Yours is faster and produces shorter chains.  I shortened it a
> tiny bit.
>
[ clipped ]

Shorter still:

dict = Hash.new{|h,k| h[k] = [] }
IO.foreach($*[2] || 'words.txt') do |w| w.chomp!
  next if w.size != $*[0].size
  w.size.times{|i| dict[w[0,i]+"."+w[i+1..-1]] << w}
end
t, known = {$*[1], 0}, {}
while !known.merge!(t).key?($*[0])
  t = t.keys.inject({}){|h, w| (0...w.size).each{|i| s=w.dup
    s[i]=?.; dict[s].each{|l| h[l] = w if !known[l] }}; h }
  warn 'no way!' or exit if t=={}
end
puts w = $*[0]; puts w while (w = known[w]) != 0