http://www.cppblog.com/doing5552/archive/2009/01/08/71532.html
http://anony3721.blog.163.com/blog/static/51197420114215753871/
http://blog.csdn.net/nauty_li/article/category/374761
http://cowboy.1988.blog.163.com/blog/static/7510579820101018113122815/?fromdm&fromSearch&isFromSearchEngine=yes