解说传送门:http://neroysq.blogcn.com/articles/%E5%90%8E%E7%BC%80%E8%87%AA%E5%8A%A8%E6%9C%BA%E5%88%9D%E6%8E%A2.html
应用传送门:http://neroysq.blogcn.com/articles/spoj%E5%90%8E%E7%BC%80%E8%87%AA%E5%8A%A8%E6%9C%BA%E5%BA%94%E7%94%A8.html