Prefix tree implementation for C - c

Question

I am trying to write a C program that provides autocomplete suggestions looking at the contents of a directory. I have most of it done, however I get errors where directory names contain symbols that are not alphabets (such as . , / _). I get errors whenever I try to change things, including array size and looping values. Could you please take a look at my code and suggest what changes I need to make to include symbols in autocomplete suggestions.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dirent.h>
#define MAX 1000
struct node {
int data;
struct node *array[26];
};
struct node* new_node(struct node *h)
{
int i;
h = malloc(sizeof (struct node));
for (i = 0; i < 24; ++i)
h->array[i] = 0;
return h;
}
struct node* insert(struct node *h, char *c, int value)
{
int i;
if (strlen(c) == 0)
return h;
if (h == NULL)
h = new_node(h);
struct node *p = h;
for (i = 0; i < strlen(c); ++i) {
if (p->array[c[i] - 'a'] == NULL)
p->array[c[i] - 'a'] = malloc(sizeof (struct node));
p = p->array[c[i] - 'a'];
}
p->data = value;
return h;
}
int dfs(struct node *h, char *dat)
{
int i;
char k[1000] = {0};
char a[2] = {0};
if (h == NULL)
return 0;
if (h->data > 0)
printf("Match: %s\n", dat);
for(i = 0; i < 26; ++i) {
strcpy(k, dat);
a[0] = i + 'a';
a[1] = '\0';
strcat(k, a);
dfs(h->array[i], k);
}
}
void search(struct node *h, char *s, char *dat)
{
int i;
char l[1000] = {0};
char a[2];
strcpy(l, dat);
if (strlen(s) > 0) {
a[0] = s[0];
a[1] = '\0';
if(h->array[a[0]-'a'] != NULL) {
strcat(dat, a);
search(h->array[a[0]-'a'], s+1, dat);
} else
printf("No Match \n");
} else {
if (h->data != 0)
printf("Match: ");
for (i = 0; i < 26; ++i) {
strcpy(l, dat);
a[0] = i + 'a';
a[1] = '\0';
strcat(l, a);
dfs(h->array[i], l);
}
}
}
struct node* read_keys(struct node *h, char *file)
{
char s[MAX];
FILE *a = fopen(file, "r");
if (a == NULL)
printf("Error while opening file");
else
while (feof(a) == 0) {
fscanf(a, "%s", s);
h = insert(h, s, 1);
}
return h;
}
int main()
{
DIR *d;
struct dirent *dir;
char direct[MAX];
printf("Enter a folder name: ");
scanf("%s",direct);
d = opendir(direct);
FILE *f = fopen("file.txt", "w");
if (f == NULL)
{
printf("Error opening file!\n");
exit(1);
}
if (d)
{
while ((dir = readdir(d)) != NULL)
{
fprintf(f,"%s\n", dir->d_name);
}
}
fclose(f);
char c[1000];
FILE *fptr;
if ((fptr = fopen("file.txt", "r")) == NULL)
{
printf("Error! opening file");
exit(1);
}
FILE* file = fopen("file.txt", "r");
char line[1000];
while (fgets(line, sizeof(line), file)) {
printf("%s", line);
}
fclose(fptr);
printf("Enter beginning of filename \n");
struct node *h = 0;
h = read_keys(h, "file.txt");
char s[MAX];
scanf("%s", s);
char dat[1000] = "";
search(h, s, dat);
return 0;
}