#include<stdio.h>
#include<conio.h>
#include<alloc.h>


struct book
{
 int code;
 char name [30];
 struct book*pleft;
 struct book*pright;
};

//add function
 struct book* add(struct book*proot,struct book*pleaf,struct book*pnode)
 {

     if (!pleaf)
     {
	 pnode->pleft=NULL;
	 pnode->pright=NULL;
	 if (proot)
	 {
		if (pnode->code<=proot->code)
			proot->pleft=pnode;
		else
		{
		 proot->pright=pnode;
		}
		return proot;
	  }


	return pnode;
	}

	if(pnode->code<=pleaf->code)
	  {add(pleaf,pleaf->pleft,pnode);
	  }
	else
	    {add (pleaf,pleaf->pright,pnode);
	    }



  return proot;
 }




//search function
 struct book* search(struct book*proot,int code)

 {
   while (proot && proot->code!=code)
    {
     if (proot->code>=code)
       {proot=proot->pleft;
       }
     else
       {proot=proot->pright;
       }

    }return proot;
 }

// print function
void print (struct book*proot)
  {
   if (proot)
    {print(proot->pleft);
     printf("%d%s",proot->code,proot->name);
     print(proot->pright);
    }


  }


// main

void main()
{
clrscr ();
 int x;
struct book*proot=NULL;
struct book*pnode;
while(x!=000)
{
printf("\n\t            to add a book enter 1\n \
		    to search for a book enter 2\n \
		    to print book list enter 3\n\
		    to Quit enter 000\n");

scanf("%d",&x);
switch (x)
{
 case 1:
       pnode=(struct book*)malloc(sizeof(struct book));
       printf("enter book code\n");
       scanf("%d",&pnode->code);
       printf("enter book name\n");
       scanf("%s",&pnode->name);

       proot=add(proot,proot,pnode);

 break;
 case 2:
       struct book*ps;

       int code;
       printf("enter code\n");
       scanf("%d",&code);
       ps=search(proot,code);
       printf("%d%s",ps->code,ps->name);
 break;

 case 3:
	print(proot);
 break;

 default:
 break;

}

}

}










/*
struct mem*phead=NULL;
struct mem*ptail=NULL;
struct mem
{int code;
char name[30];
struct mem*pn;
struct mem*pp;
};

//Add function

void addNode(struct mem*pnode)

{if(!phead)
 {phead=pnode;
  ptail=pnode;
  pnode->pn=NULL;
  pnode->pp=NULL;
 }
 else
 {ptail->pn=pnode;
 pnode->pp=ptail;
 ptail=pnode;
 ptail->pn=NULL;
 }
}

// find function

struct mem*find(int x)
{struct mem*ptr;
ptr=phead;
while(ptr&&ptr->code!=x)
{ptr=ptr->pn;
}
return ptr;
}

//delete function

int deleteNode (int code)

{struct mem*pnode;
 int delflag=0;
 pnode=find(code);

 if (pnode)

 {
     if(pnode==phead)
     {phead=phead->pn;
      phead->pp=NULL;
     }
     else if (pnode==ptail)
     {ptail=ptail->pp;
      ptail->pn=NULL;
     }
     else
     {pnode->pn->pp=pnode->pp;
      pnode->pp->pn=pnode->pn;
     }
 free (pnode);
 delflag=1;

 }
 return delflag;

};

//insert function

void insert (struct mem *pnode)
 {struct mem *ptrans;
  if (!phead)

  {addNode (pnode);}

  else
  {
   ptrans=phead;
   while(ptrans&&ptrans->code<pnode->code)
    {ptrans=ptrans->pn;}
     if (ptrans==phead)
      {pnode->pp=NULL;
       pnode->pn=phead;
       phead->pp=pnode;
       phead=pnode;

      }
     else if(!ptrans)
      {pnode->pp=ptail;
       pnode->pn=NULL;
       ptail->pn=pnode;
       ptail=pnode;
      }
     else
       {
       pnode->pn=ptrans;
       pnode->pp=ptrans->pp;
       pnode->pp->pn=pnode;
       ptrans->pp=pnode;
       }
  }

 }

// print function

void printList()
{struct mem*ptrans;
 ptrans=phead;

 while(ptrans)
 {printf("%d",ptrans->code);
  printf("%s",ptrans->name);
  ptrans=ptrans->pn;

 }

}


// free function

void freeList ()
{ struct mem*ptrans;

  while(ptrans)
  { ptrans=phead;
   phead=phead->pn;

  free (ptrans);
  }
  }

void main()
{
clrscr ();
 int x;
struct mem*pnode;
while(x!=000)
{
printf("            to add a member enter 1\n \
		    to find a member enter 2\n \
		    to delete a member enter 3\n\
		    to insert a member enter 4\n\
		    to print member list enter 5\n\
		    to free member list enter 6\n\
		    To Quit enter 000\n");

scanf("%d",&x);
switch (x)
{
 case 1:

pnode=(struct mem*)malloc(sizeof(struct mem));
printf("enter member code\n");
scanf("%d",&pnode->code);
printf("enter member name\n");
scanf("%s",&pnode->name);
addNode(pnode);
break;
 case 2:
 int y;
 printf("Enter Member Code\n\t");
 scanf("%d",&y);
     pnode=find(y);
     printf("\tMember Code\t%d\n\t",pnode->code);
     printf("Member Name\t%s\n\t",pnode->name);
 break;

 case 3:
 printf("Enter Member Code\n\t");
 scanf("%d",&y);
   int z= deleteNode (y);
   if (z==1)
   {printf("\nMember Deleted");}
   else
   {printf("\nList Is Embty");}
     break;

 case 4:

  pnode=(struct mem*)malloc(sizeof(struct mem));
  printf("enter member code\n");
  scanf("%d",&pnode->code);
  printf("enter member name\n");
  scanf("%s",&pnode->name);
  insert (pnode);
    break;

 case 5:
  printList ();
  break;


 case 6:
  freeList ();
  printf("List Freed");
  break;

 default:
 break;

}
 }

} */







// this is my code , check out the borrowBook and the returnBook functions . BTW I am not sure this works, it just compiles fine.



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


#define NLEN 30
struct book 
{
	int isbn;
	char name[NLEN];
	char auther[NLEN];
	char publisher[NLEN];
	struct user *hasMe;

	struct book *left;
	struct book *right;
};

struct user 
{
	int id;
	char name[NLEN];
	char address[NLEN];
	struct book *borrowed;

	struct user *next;
	struct user *prev;
};

struct user *head;
struct user *tail;



void addToList (struct user *p)
{
	if (!head)
	{
		head = p;
		tail = p;
		p->next = NULL;
		p->prev = NULL;
	}
	else
	{
		tail->next = p;
		p->prev = tail;
		p->next = NULL;
		tail = p;
	}
}

struct user *searchInList(int x)
{
	struct user *ptr;
	ptr = head;
	while (ptr && ptr->id != x)
		ptr = ptr->next;
	return (ptr);
}

int deleteFromList(int id)
{
	struct user *ptr;
	int delFlag = 0;
	ptr = searchInList(id);
	if (ptr)
	{
		if (ptr == head)
		{
			head = head->next;
			head->prev = NULL;
		}
		else if (ptr == tail)
		{
			tail = tail->prev;
			tail->next = NULL;
		}
		else
		{
			ptr->next->prev = ptr->prev;
			ptr->prev->next = ptr->next;
		}
		free(ptr);
		delFlag = 1;
	}
	return delFlag;
}

int borrowBook(struct user *u, struct book *b)
{
	if (u->borrowed)
		return 1;
	else if (b->hasMe)
		return 2;
	else
	{
		u->borrowed = b;
		b->hasMe = u;
		return 0;
	}
} 

void returnBook(struct user *u, struct book *b)
{
	u->borrowed = NULL;
	b->hasMe = NULL;
}

struct book *addToTree (struct book *root, struct book *leaf, struct book *p)
{
	if (!leaf)
	{
		p->left = NULL;
		p->right = NULL;

		if (root)
		{
			if (p->isbn <= root->isbn)
				root->left = p;
			else
				root->right = p;
			return root;
		}
		return p;
	}
	if (p->isbn <= leaf->isbn)
		addToTree (leaf, leaf->left, p);
	else
	      	addToTree (leaf, leaf->right, p);
	return root;

} 

struct book *searchInTree ( struct book *root, int x)
{
	while (root && root->isbn != x)
	{
		if (root->isbn >= x)
			root = root->left;
		else
		root= root->right;

	}
	return root;
}

		
int main ()
{
	//clrscr();
	struct book *p;
	struct book *root;
	struct user *u;
	int x, y, z;
	while (1)
	{
		printf("Please select an operation:\n\n");
		
		printf("\t1.Add a book\n\t2.Find a book\n\t3.Borrrow a book\n\t4.Add a user\n\t5.Find a user\n\t6.Delete a user\n\t7.Return a book\n\t8.Exit\n");
		printf("Selection: ");
		scanf("%d", &y);
		switch (y)
		{
			case 1: // add a book
				p = (struct book *) malloc (sizeof(struct book));
				printf ("Enter the ISBN: ");
				scanf("%d", &p->isbn);
				printf("Enter the book name: ");
				scanf("%s", p->name);
				printf("Enter the auther name: ");
				scanf("%s", p->auther);
				printf("Enter the publisher: ");
				scanf("%s", p->publisher);
				p->hasMe = NULL;
				root = addToTree(root, root, p);
				break;
			case 2: // find a book
				printf("Enter the ISBN: ");
				scanf("%d", &x);
				p = searchInTree (root, x);
				if (!p)
					printf("\nBook not found!\n");
				else
					printf("\n->Code: %d\n->Name: %s\n->Auther: %s\n->Publisher:%s", p->isbn, p->name, p->auther, p->publisher);
				break;
			case 3:  // borrow a book
				printf("Enter the book's ISBN: ");
				scanf("%d", &x);
				printf("Enter the user's ID: ");
				scanf("%d", &z);
				if(borrowBook (searchInList (z), searchInTree (root, x)))
					printf("Book is not available or user already has a book!\n");
				else
					printf("done!\n");
				break;
			case 4: // add a user
				u = (struct user *) malloc (sizeof(struct user));
				printf("Enter the user ID: ");
				scanf("%d", &u->id);
				printf("Enter the user name: ");
				scanf("%s", u->name);
				printf("Enter the user address: ");
				scanf("%s", u->address);
				u->borrowed = NULL;
				addToList (u);
				
				break;
			case 5: // find a user
				printf("Enter the user ID: ");
				scanf("%d", &x);
				u = searchInList (x);
				if (!u)
					printf("User not found!\n");
				else 
					printf("->ID: %d\n->Name: %s\n->Address: %s\n", u->id, u->name, u->address);
				
			case 6:  //delete a user
				printf("Enter the user ID: ");	
				scanf("%d", &x);
				if (!deleteFromList (x))
					printf("Can't delete user!\n");
				
				break;
			case 7: // return a book
				printf("Enter the book's ISBN: ");
				scanf("%d", &x);
				printf("Enter the user's ID: ");
				scanf("%d", &z);
				returnBook (searchInList (z), searchInTree (root, x));
				break;
			case 8:
				return (0);
				break;

			default:
				printf("Invalid operation!\n");
				break;
		}
	}
	return 0;
}