字典树实现

字典树，插入时检测单词是否存在。

#include 
#include 
#include 
#include 

/*默认只处理26个小写字母
 *将小写字母转换为数字
 */
#define MAX 26
typedef struct word_node
{
    bool is_word_end;
    int num;  //字母-'a'后的数字
    struct word_node* next[MAX];
}word_node_t;

#define INSERT_FAIL -1
#define INSERT_SUCCESS 0
#define INSERT_EXIST 1

word_node_t *create_word(const int num)
{
    word_node_t *p = (word_node_t*)malloc(sizeof(word_node_t));
    if (p == NULL)
    {
        printf("malloc error\n");
        exit(1);
    }
    memset(p->next, 0, MAX);
    p->is_word_end = false;
    p->num = num;

    return p;
}

//调用时，root必须存在且不为NULL
int insert_word(const char *str, word_node_t *pos)
{
    const int str_length = strlen(str);
    int i;
    for (i = 0; i < str_length; ++i)
    {
        int num = str[i] - 'a';
        if (pos->next[num] == NULL)
        {
            pos->next[num] = create_word(num);
        }
        pos = pos->next[num];
    }

    if (pos->is_word_end)  //已存在单词或字串与插入单词相同
      return INSERT_EXIST;
    else
    {
        pos->is_word_end = true;
        return INSERT_SUCCESS;
    }
}

void free_tree(word_node_t *root)
{
    int i;
    for (i = 0; i < MAX; ++i)
    {
        if (root->next[i] != NULL)
        {
            free_tree(root->next[i]);
            root->next[i] = NULL;
        }
    }
    free(root);
}

int main(int argc, char **argv)
{
    word_node_t *root = create_word(-1);
    char *a[] = {"abc", "abcd", "abcde", "abc", "bcd", "bbde", "bbde", "abcd", "xyz", "xy", "xyz"};
    int i;
    int result;
    for (i = 0; i < sizeof(a)/sizeof(char*); ++i)
    {

        if ((result = insert_word(a[i], root)) == INSERT_EXIST)
        {
            printf("exit:%s\n", a[i]);
        }
        else if (result == INSERT_SUCCESS)
          printf("success:%s\n", a[i]);
    }
    free_tree(root);
}