Pointers and binary search tree - c

Question

I am working on a program that uses a binary search tree (as an exercise).
My problem is that when I try to add a customer(in the middle of my code lines 65-69) I get an error that BS_node is undeclared, though I insert struct BST_node *root in this function..
Part of my code is below, just for the readers to read it easier, if requested I can upload the full code ! Thanks!
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_STRING 50
void flush();
struct customer {
char *name;
char *address;
char *email;
};
struct double_linked_list {
struct customer *data;
struct double_linked_list *previous;
struct double_linked_list *next;
};
struct double_linked_list *customers_head=0;
struct BST_node {
struct double_linked_list *data;
struct BST_node *left;
struct BST_node *right;
};
struct BST_node *BST_email_root = 0;
struct BST_node *BST_find_customer(struct BST_node *root, char *email) {
if (root==NULL)
return NULL;
if (strcmp(email,root->data->data->email)==0)
return root;
else
{
if (strcmp(email,root->data->data->email)==-1)
return BST_find_customer(root->left,email);
else
return BST_find_customer(root->right,email);
}
}
void find_customer() {
char email[MAX_STRING];
struct double_linked_list *l;
struct BST_node *b;
printf("Give the email of the customer (up to %d characters) : ", MAX_STRING-1);
gets(email);
b = BST_find_customer(BST_email_root, email);
if (b==0)
printf("There is no customer with this email.\n");
else
{
l = b->data;
printf("Customer found! \n");
printf("Name : %s\n", l->data->name);
printf("Address : %s\n", l->data->address);
printf("Email : %s\n", l->data->email);
}
}
struct BST_node *new_BST_node(struct BST_node *root, struct double_linked_list *l)
{
if (root==NULL);
{
root = (BST_node *) malloc (sizeof(BST_node ));
if (root==NULL)
{
printf("Out of Memory!");
exit(1);
}
root->data=l;
root->left=NULL;
root->right=NULL;
}
if (strcmp(l->data->email,root->data->data->email)==-1)
root->left =new_BST_node(root->left,l);
else root->right =new_BST_node(root->right,l);
return root;
};
struct double_linked_list *new_customer()
{
char name[MAX_STRING], address[MAX_STRING], email[MAX_STRING];
struct BST_node *b;
struct double_linked_list *l;
struct customer *c;
printf("\nADDING NEW CUSTOMER\n=\n\n");
printf("Give name (up to %d characters): ", MAX_STRING-1);
gets(name);
printf("Give address (up to %d characters): ", MAX_STRING - 1);
gets(address);
printf("Give email (up to %d characters): ", MAX_STRING - 1);
gets(email);
b = BST_find_customer(BST_email_root, email);
if (b)
{
printf("Duplicate email. Customer aborted.\n");
return 0;
}
c = (struct customer *) malloc(sizeof(struct customer));
if (c == 0)
{
printf("Not enough memory.\n");
return 0;
}
c->name = strdup(name); // check for memory allocation problem
if (c->name == 0) return 0;
c->address = strdup(address); // check for memory allocation problem
if (c->address == 0) return 0;
c->email = strdup(email); // check for memory allocation problem
if (c->email == 0) return 0;
l = (struct double_linked_list*) malloc(sizeof(struct double_linked_list));
if (l == 0)
{
printf("Not enough memory.\n");
free(c->name);
free(c->address);
free(c->email);
free(c);
return 0;
}
l->data = c;
l->previous = 0;
l->next = customers_head;
if (customers_head)
customers_head->previous = l;
customers_head = l;
BST_email_root = new_BST_node(BST_email_root, l);
return l;
}
void displaymenu() {
printf("\n\n");
printf("1. New customer\n");
printf("2. Find customer using email\n");
printf("0. Exit\n\n");
printf("Give a choice (0-6) : ");
}
void flush()
{
char ch;
while ((ch = getchar()) != '\n' && ch != EOF);
}
int main() {
int choice;
do {
displaymenu();
scanf("%d", &choice);
flush();
switch (choice) {
case 1:
new_customer();
break;
case 2:
find_customer();
break;
} while (choice != 0);
return 0;
}

Answer 1

On the line 69, you have to specify struct BST_node instead of BST_node:
root = (struct BST_node *) malloc (sizeof(struct BST_node ));
As for the rest of the code: read the manual for gets, it's clearly a function one should not use, I'd advise replacing it with fgets. There's also a little closing bracket missing in your final switch (line 178).