Trie树检索字符串

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

typedef struct TrieNode_t
{
    char data;
    short int end_flag;//字符串完全添加标志位
    struct TrieNode_t* child_node[];
} TrieNode;

TrieNode root = {  };

//添加字符串到树中
void InsertString(char a[], int len)
{
    int i;
    TrieNode *p = &root;
    for (i = ; i < len; i++)
    {
        int index = a[i] - 'a';
        if (p->child_node[index] == )
        {
            TrieNode *p_child = (TrieNode *)malloc(sizeof(struct TrieNode_t));
            if (NULL == p_child)
            {
                printf("malloc fail\n");
                return;
            }
            p_child->data = a[i];
            p->child_node[index] = p_child;
        }
        p = p->child_node[index];
    }
    p->end_flag = ;
}

//查询字符串，时间复杂度为O(len)
int SearchString(TrieNode root, char a[], int len)
{
    int i;
    TrieNode *p = &root;
    for (i = ; i < len; i++)
    {
        int index = a[i] - 'a';
        if (p->child_node[index] == )
        {
            return -;
        }
        p = p->child_node[index];
    }

    if (p->end_flag == )
    {
        return ;
    }
    else
    {
        return -;
    }
}

int main()
{
    char a[] = "helloworld";
    char b[] = "gelloworld";
    char c[] = "helltworld";
    char d[] = "helloworlr";
    char e[] = "hello";
    InsertString(a, );
    printf("%d\n", SearchString(root, e, ));
    return ;
}