From:http://hi.baidu.com/aekdycoin/item/90065df1b0f5b412ce9f32d6
Wiki:http://en.wikipedia.org/wiki/Dancing_Links
论文参考:http://gaoyunxiang.com/wp-content/uploads/2010/02/Dancing_Links.pdf
Dancing Links
http://acm.hust.edu.cn/problem.php?id=1017
过程:http://en.wikipedia.org/wiki/Algorithm_X
模板题,测试模板的正确性。