[搜索]Trie树的一种实现

trie树也叫字典树，搜索树等。

如图所示

下面是用stl 的map来实现

class trie_item_c
{
public:
	trie_item_c(){}
	trie_item_c(const char nm)
	{
		name = nm;
	}

	void set_name(const char nm)
	{
		name = nm;
	}

	trie_item_c * get_child(const char nm)
	{
		map<const char ,trie_item_c*>::const_iterator it = children.find(nm);
		if(it != children.end())
			return it->second;
		else
		{
			trie_item_c *cld = new trie_item_c(nm);
			children.insert(pair <const char ,trie_item_c*>(nm,cld));
			return cld;
		}
	}
	bool find(const char* dic)
	{
		if(!dic || *dic == '\0')
		{
			if(children.end() != children.find('\0'))
				return true;
			return false;
		}
		const char* temp = dic;
		map<const char ,trie_item_c*>::const_iterator it = children.find(*temp);
		if(it == children.end())
			return false;
		return it->second->find(++temp);
	}
	void print()
	{
		printf("%c",name);
		map<const char ,trie_item_c*>::const_iterator it = children.begin();
		for(;it != children.end();it++)
		{
			it->second->print();
		}
		printf("\n");
	}
	virtual ~trie_item_c()
	{
		map<const char ,trie_item_c*>::const_iterator it = children.begin();
		while(it != children.end())
		{
			delete it->second;
			children.erase(it);
			it = children.begin();
		}
	}
private:
	map<const char ,trie_item_c*> children;
	char name;

};

下面代码是构建树的过程

for(const char* dic = lst.first_string();dic;dic = lst.next_string())
	{

		trie_item_c *temp = root;
		for(int i=0;i<str_temp.str_len();i++)
		{
			char c = str_temp.get(i);
			trie_item_c *item = temp->get_child(c);
			temp = item;
		}
		//add one null child
		temp->get_child('\0');
	}

判断一个单词是否在root中，只需要调用root->find("book");即可。