什么是trie树？
◇ trie树是一种用于快速检索的多叉树结构。
◇ 和二叉查找树不同，在trie树中，每个结点上并非存储一个元素。
◇ trie树把要查找的关键词看作一个字符序列。并根据构成关键词字符的先后顺序构造用于检索的树结构。
◇在trie树上进行检索类似于查阅英语词典。
一棵m度的trie树或者为空，或者由m棵m度的trie树构成。例如，电子英文词典，为了方便用户快速检索英语单词，可以建立一棵trie树。例如词典由下面的单词构成：a、b、c、aa、ab、ac、ba、ca、aba、abc、baa、bab、bac、cab、abba、baba、caba、abaca、caaba
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#define MAXN 10010
#define RST(N)memset(N, 0, sizeof(N))
using namespace std;
const int char_num = 26;
class Trie {
public:
Trie();
int trie_search(const char* word, char* entry) const;
int insert(const char* word, char* entry);
int remove(const char* word, char* entry);
protected:
struct Trie_node {
char *data;
Trie_node *branch[char_num]; //指向各個子樹的指針
Trie_node();
};
Trie_node *root;
};
Trie::Trie() : root(NULL) {};
Trie::Trie_node::Trie_node()
{
data = NULL;
for(int i=0; i<char_num; i++) branch[i]=NULL;
}
int Trie::trie_search(const char *word, char *entry) const //检索
{
int position = 0;
char char_code;
Trie_node *location = root;
while(location != NULL && *word != 0) {
if(*word>='a' && *word<='z') char_code = *word-'a';
else if(*word>='A' && *word<='Z') char_code = *word-'A';
else return 0; //不合法單詞
location = location->branch[char_code];
position++, word++;
}
if(location != NULL && location->data != NULL) {
strcpy(entry, location->data);
return 1;
}
return 0;
}
int Trie::insert(const char *word, char *entry) //插入
{
int result = 1, position = 0;
if(root == NULL) root = new Trie_node;
char char_code;
Trie_node *location = root;
while(location != NULL && *word != 0) {
if(*word>='a' && *word<='z') char_code = *word-'a';
else if(*word>='A' && *word<='Z') char_code = *word-'A';
else return 0; //不合法單詞
if(location->branch[char_code] == NULL)
location->branch[char_code] = new Trie_node;
location = location->branch[char_code];
position++, word++;
}
if(location->data != NULL) result = 0;
else {
location->data = new char(strlen(entry)+1);
strcpy(location->data, entry);
}
return result;
}
int main()
{
Trie t;
char entry[100];
t.insert("a", "DET"); t.insert("abacus","NOUN");
t.insert("abalone","NOUN"); t.insert("abandon","VERB");
t.insert("abandoned","ADJ"); t.insert("abashed","ADJ");
t.insert("abate","VERB"); t.insert("this", "PRON");
if (t.trie_search("this", entry))
cout<<"'this' was found. pos: "<<entry<<endl;
if (t.trie_search("abate", entry))
cout<<"'abate' is found. pos: "<<entry<<endl;
if (t.trie_search("baby", entry))
cout<<"'baby' is found. pos: "<<entry<<endl;
else
cout<<"'baby' does not exist at all!"<<endl;
return 0;
}
原文：http://blog.csdn.net/keshacookie/article/details/40082133