国外的一个人写的小程序。

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CODE:

#Josh Goebel


class HanoiRack
  class Peg
    attr_reader :id, :rings
    def initialize( id )
      @id = id
      @rings = []
    end
    def push( ring_size )
      if @rings.last < ring_size
       raise "Cannot put #{ring_size} on top of #{@rings.last}"
      end unless @rings.empty?
      @rings << ring_size
    end
    def pop
      raise "No rings on peg #{self} left to pop!" if @rings.empty?
      @rings.pop
    end
    def ring_count
      @rings.length
    end
    def to_s
      "<Peg #@id>"
    end
    alias_method :inspect, :to_s
  end
end

class HanoiRack
  attr_reader :pegs
  def initialize( largest_ring_size=7 )
    @pegs = [
      Peg.new( :A ),
      Peg.new( :B ),
      Peg.new( :C )
    ]
    @largest_ring_size = largest_ring_size
    @largest_ring_size.downto(1){ |ring_size| @pegs[0].push(ring_size) }
    @max_rings = @pegs[0].ring_count
  end
  
  def move_stack( source_peg, dest_peg, num_rings=source_peg.ring_count )
    spare_peg = @pegs.find{ |peg| peg!=source_peg && peg!=dest_peg }
    if num_rings == 1
      move_ring( source_peg, dest_peg )
    else
      move_stack( source_peg, spare_peg, num_rings-1 )
      move_ring( source_peg, dest_peg )
      move_stack( spare_peg, dest_peg, num_rings-1 )
    end
  end
  
  # Move the topmost ring off one peg and onto another
  def move_ring( source_peg, dest_peg )
    dest_peg.push( source_peg.pop )
    puts self, " "
  end
  
  def to_s
    s = ""
    widest_ring = @largest_ring_size * 2 - 1
    @max_rings.downto( 0 ){ |stack_spot|
      s << @pegs.map{ |peg|
        if ring_size = peg.rings[ stack_spot ]
          ( '-' * (ring_size*2-1) ).center( widest_ring )
        else
          peg.id.to_s.center( widest_ring )
        end
      }.join( ' ' ) + "\n"
    }
    s
  end
end  

if __FILE__ == $0
  r = HanoiRack.new( 5 )
  puts r, " "
  r.move_stack( r.pegs.first, r.pegs.last )
end

代码显示有问题啊

它是干嘛用的？

你没玩过汉诺塔啊?