Trie的一個實現

Trie.h 檔案

#ifndef _TRIE_H
#define _TRIE_H

#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <algorithm>
using namespace std;

inline int sub_size(int level)
{
     return level > 5 ? 1 : 256 / (level * level * level);
}   

struct search_tree
{
    search_tree(int level)
    {
        int len = sub_size(level);
        word = false;
        sub_tree = new search_tree *[len];
        next = NULL;
        for (int i = 0; i < len; i++)
            sub_tree[i] = NULL;     
    }
      
    char cchar;
    bool word;
    search_tree **sub_tree;
    search_tree *next;
};

class Trie
{
    public:
        Trie()
        {
            for (int i = 0; i < 256; i++)
                T[i] = NULL;
       }
       ~Trie()
       {
           for (int i = 0; i < 256; i++)
               search_tree_delete(T[i], 1);
       }
      int add(char *str); 
      int prefix_in_tree(char *str); 
  
    private:
         void search_tree_delete(search_tree *s_tree, int level);  
         void search_tree_add(search_tree *&s_tree, char *str, int level);
         int prefix_in_tree(search_tree *s_tree, char *str, int level);
         unsigned int hash(unsigned char cchar, int len);
         search_tree *T[256];
};

#endif

trie.cpp

#include "trie.h"
using namespace std;

unsigned int Trie::hash(unsigned char cchar, int len)
{
     return cchar % len;
}

int Trie::add(char *str)
{
     int hash_code = hash((unsigned char)(*str), 256);
     search_tree_add(T[hash_code], str, 1);
     return 1;
}
   
int Trie::prefix_in_tree(char *str)
{
    return prefix_in_tree(*(T + (unsigned char)(*str)), str, 1);
}

void Trie::search_tree_add(search_tree *&s_tree, char *str, int level)
{
    search_tree *cur = NULL;
    if (s_tree == NULL)
    {
        s_tree = new search_tree(level + 1);
        s_tree->cchar = *str;
        cur = s_tree;
    }
    else
    {
        if (s_tree->cchar != *str)
        {
            s_tree->next = new search_tree(level + 1);
            s_tree->next->cchar = *str;
            cur = s_tree->next;
       }
      else
           cur = s_tree;
    }
 
     if (*(str + 1) == '/0')
     {
         cur->word = true;
         return;
     }
 
    int hash_code = hash(*(str + 1), sub_size(level + 1));
    search_tree_add(cur->sub_tree[hash_code], str + 1, level + 1);  
    return;
}   

int Trie::prefix_in_tree(search_tree *s_tree, char *str, int level)
{   
    if (s_tree == NULL || *str == '/0')
    return 0;

    int hash_code;

    for (search_tree *cur = s_tree; cur != NULL; cur = cur->next)
    {
        if (cur->cchar == *str)
        {
             if (cur->word)
             return level;
   
             hash_code = hash(*(str + 1), sub_size(level + 1));
             return prefix_in_tree(cur->sub_tree[hash_code], str + 1, level + 1);
        }
    }
       
    return 0;
}

void Trie::search_tree_delete(search_tree *s_tree, int level)
{
    if (s_tree == NULL)
        return;

    search_tree_delete(s_tree->next, level);
     int len = sub_size(level + 1);
     for (int i = 0; i < len; i++)
     {
         search_tree_delete(s_tree->sub_tree[i], level + 1);
     }
     delete s_tree;
}