c++ 前缀树

Trie树，又称字典树，单词查找树或者前缀树，是一种用于快速检索的多叉树结构，如英文字母的字典树是一个26叉树，数字的字典树是一个10叉树。

Trie树可以利用字符串的公共前缀来节约存储空间。

 

参考：http://hi.baidu.com/zealot886/item/08ef4cbe791c404ebb0e124f

下面是我自己实现的trie树

#include <iostream>
#include <string>
#include <set>
#include <fstream>
using namespace std;
#define MAXSIZE 26
class TrieNode
{
public:
	int freq;
	char nodechar;
	TrieNode *children[MAXSIZE];
    set<int> hashset;
	TrieNode()
	{
		for(int i=0; i<MAXSIZE; i++)
		{
			children[i] = NULL;
		}
		freq = 0;
	}
};

class TrieTree
{
public:
	void AddTrieNode(TrieNode *root, string word, int id);
	void DeleteTrieNode(TrieNode *root, string word);
	int wordCount( TrieNode *root, string word);
	set<int> SearchTrie( TrieNode *root,string word);
	TrieTree()
	{
		p_root = new TrieNode();
	}
public:
	TrieNode *p_root;
 };

void TrieTree::AddTrieNode(TrieNode *root, string word, int id)
{
 //cout<<word<<endl;
	if(word.length() == 0)
	{return ;}
	int k = tolower(word.at(0)) - 'a';
	if(root->children[k] == NULL)
	{
		root->children[k] = new TrieNode();
		root->children[k]->nodechar = word.at(0);
	}
	root->children[k]->freq++;
	root->children[k]->hashset.insert(id);
	string nextword = word.substr(1, string::npos);
 
	AddTrieNode(root->children[k], nextword, id);
}

void TrieTree::DeleteTrieNode(TrieNode *root, string word)
{
	if(word.length() == 0)
	{return ;}
	int k = word.at(0) - 'a';
	if(root->children[k] == NULL)
	{return ;}
	if (root->children[k]->freq > 0)
	{
		root->children[k]->freq--;
	}
   
	string nextword = word.substr(1, string::npos);
	DeleteTrieNode(root->children[k], nextword);
}

int TrieTree::wordCount(TrieNode *root, string word)
{
	if(root == NULL)
	{return 0;}
	int num = 0;
	int k = word.at(0) - 'a';
	string nextword = word.substr(1, string::npos);
	if(nextword.length() == 0)
	{
		num = root->children[k]->freq;
	}
	else
	{
		if(root->children[k] != NULL)
		{
			num = wordCount(root->children[k], nextword);
		}
	}
 return num;
}

set<int> TrieTree::SearchTrie( TrieNode *root, string word)
{
	set<int> rset;
	if(root == NULL || word.length() == 0)
	{
		cout<<"str is null"<<endl;
		return rset;
	}
	int k = word.at(0) - 'a';
	string nextword = word.substr(1, string::npos);
	if(root->children[k] == NULL)
	{
		return rset;
	}
	if(nextword.length() == 0)
	{
		return root->children[k]->hashset;
	}
	if (root->children[k] != NULL)
	{
		rset = SearchTrie(root->children[k], nextword);
	}
 
 return rset;
}