回文数の数

今週のアルゴリズムで既出の問題ですね…
cf: https://github.com/cielavenir/codeiq_solutions/blob/master/thisweek_masuipeo/tyama_codeiq575_mod.rb

#!/usr/bin/env ruby
#http://nabetani.sakura.ne.jp/hena/orde17palin/
#http://qiita.com/Nabetani/items/aa15539c8dc2c610c1a0
def solve(t,b=10)
    return to_enum(:solve,t,b) if !block_given?
    (0...b).each{|i|return if i>t;yield i}
    start=1
    digit=1
    loop{
        start.step(start*b-1){|i|
            s=i.to_s(b)
            n=(s+s.reverse).to_i(b)
            return if n>t
            yield n
        }
        start.step(start*b-1){|i|
            s=i.to_s(b)
            (0...b).each{|mid|
                n=(s+mid.to_s(b)+s.reverse).to_i(b)
                return if n>t
                yield n
            }
        }
        start*=b
        digit+=b
    }
end

while gets
    x,y,b=$_.split(',').map &:to_i
    p solve(y-1,b).to_a.size-solve(x-1,b).to_a.size
    STDOUT.flush
end