“hiho” is a weekly series of contest we developed to help programmers improve their skills following some architecture. And for the beginning of this series, we present the "String". Dealing with strings is a very common problem when you go into the real world as a programmer. Although we usually use the standard methods to deal with them, these standard methods actually contain a lot of brilliant ideas inside them. So we think it's a good idea to hiho some typical string problems to all of you, as it will help hone your programming thinking.

And this problem "Trie graph" is a fantasic way to solve the problem that Mr.Hexie presented at the very beginning in hiho! week3 - "How to search a serial of special words in a long text."!

Ho's hint: It wound be better to finish hiho! week2 and hiho! week3 first.

After the end of this contest, we will publish the source code of little HO and all the participants that solved this problem. Wish you learn from each other and make improvement togather!