```Hey,

My solution's similar in style [breadth first, don't duplicate search],
though I've also roof-limited it so it can't explore the search space
above 2*[max(target,start)] + 4 which provides a fair speed up for e.g.
222, 9999.  I'm not sure if that loses the optimality property though.
I can't get to the swaits.com test suite, but the other one my solver
finds smaller solutions for.

Regards,

Tris

----
require 'set'

class MazeSolver

def solve start, finish
visited = Set.new

tul, tll = if start > finish
[(start << 1) + 4, nil]
else
[(finish << 1) + 4, nil]
end

solve_it [[start]], finish, visited, tul, tll
end

def solve_it lpos, target, visited, tul, tll
n = []
lpos.each do |vs|
v = vs.last
next if tul and v > tul
next if tll and v < tll

return vs if v == target

d = v << 1                      # double
h = v >> 1 unless (v & 1) == 1  # half
p2 = v + 2                      # plus 2

n << (vs.clone << d) if visited.add? d
n << (vs.clone << h) if h and visited.add? h
n << (vs.clone << p2) if visited.add? p2
end

return solve_it(n, target, visited,tul, tll)
end
end

if __FILE__ == \$0
puts MazeSolver.new.solve(ARGV.to_i, ARGV.to_i).join(" ")
end
--------

```