Trie (in C)

Trie树的解释参见：
http://blog.csdn.net/hguisu/article/details/8131559

下面是用C实现的代码

头文件：

#ifndef TRIE_H
#define TRIE_H

#define TRIE_SIZE_DEF 128
const int TRIE_SIZE = TRIE_SIZE_DEF;

union NODE_TYPE
{
    COMPLETED;
    UNCOMPLETED;
};

typedef struct Node_
{
    union NODE_TYPE type;
    char ch;
    struct Node_ *child[TRIE_SIZE];
}trie_t;

trie_t * trie_init(void);
void trie_add(trie_t *trie, char *word);
void trie_delete(trie_t *trie, char *word);
int trie_exists(trie_t *trie, char *word);

#endif // TRIE_H

源文件：

#include <stdio.h>
#include <stdlib.h>

#include "trie.h"

static trie_t * createNewNode(char ch)
{
    trie_t *newNode = (trie_t *) malloc(sizeof(trie_t));
    newNode->ch = ch;
    newNode->type = UNCOMPLETED;
    int i;
    for (i = 0; i < TRIE_SIZE; i++)
    {
        newNode->child[i] = NULL;
    }
    return newNode;
}

static int char2int(char ch)
{
    return ch - 'a';
}

trie_t * trie_init(void)
{
    return createNewNode('');
}

void trie_add(trie_t *trie, char *word)
{
    char ch;
    while ((ch = *word++) != '\0')
    {
        if (trie->child[char2int(ch)] == NULL)
            trie->child[char2int(ch)] = createNewNode(ch);
        trie = trie->child[char2int(ch)];
    }
    trie->type =COMPLETED;
}

void trie_delete(trie_t *trie, char *word)
{
    char ch;
    while ((ch = *word++) != '\0')
    {
        if (trie->child[char2int(ch)] == NULL)
            return;
        trie = trie->child[char2int(ch)];
    }
    trie->type = UNCOMPLETED;
}

int trie_exists(trie_t *trie, char *word)
{
    char ch;
    while ((ch = *word++) != '\0')
    {
        if (trie->child[char2int(ch)] == NULL)
            return 0;
        trie = trie->child[char2int(ch)];
    }
    return (trie->tpye == COMPLETED) ? 1 : 0;
}