KMP：http://www.matrix67.com/blog/archives/115
AC自动机：
http://www.cs.uku.fi/~kilpelai/BSA05/lectures/slides04.pdf
http://blog.csdn.net/niushuai666/article/details/7002823
http://www.cppblog.com/mythit/archive/2009/04/21/80633.html