C Program to insert and delete a node from the binary search tree

#include<stdio.h>
#include<conio.h>
#include<alloc.h>
#define TRUE 1
#define FALSE 0
struct btreenode
{
   struct btreenode *leftchild;
   int data;
   struct btreenode *rightchild;
};
void insert(struct btreenode **,int);
void del(struct btreenode **,int);
void search(struct btreenode **,int,struct btreenode **,struct btreenode **,int *);
void inorder(struct btreenode *);
void main()
{
   struct btreenode *bt;
   int req;
   int i=0,num,a[]={10,7,11,5,8,12,16,15,6};
   bt=NULL; /* Empty Tree */
   clrscr();
   while(i<=8)
   {
      insert(&bt,a[i]);
      i++;
   }
   clrscr();
   printf(" Binary tree before deletion :\n");
   inorder(bt);
   del(&bt,11);
   printf("\n Binary tree after deletion :\n");
   inorder(bt);
   del(&bt,10);
   printf("\n Binary tree after deletion :\n");
   inorder(bt);
   del(&bt,6);
   printf("\n Binary tree after deletion :\n");
   inorder(bt);
   del(&bt,16);
   printf("\n Binary tree after deletion :\n");
   inorder(bt);
   getch();
}
/* inserts a new node in a binary search tree */
void insert(struct btreenode **sr,int num)
{
   if(*sr==NULL)
   {
      (*sr)=malloc(sizeof(struct btreenode));
      (*sr)->leftchild=NULL;
      (*sr)->data=num;
      (*sr)->rightchild=NULL;
   }
   else   /* Search the node to whilch new node will be attatched */
   {
       /* If new data is less, traverse to left*/
       if(num<(*sr)->data)
   insert(&((*sr)->leftchild),num);
       else
   /* Else traverse to right */
   insert(&((*sr)->rightchild),num);
   }
}
/* Deletes a node from the binary search tree */
void del(struct btreenode **root,int num)
{
   int found;
   struct btreenode *parent,*x,*xsucc;
   /* If tree is empty */
   if(*root == NULL)
   {
       printf("\n Tree is Empty ");
       return;
   }
   parent=x=NULL;
   /* Call to search function to find the node to be deleted */
   search(root,num,&parent,&x,&found);
   /* If the node to be deleted is not found */
   if(found == FALSE)
   {
     printf("\n Data to be deleted , not found ");
     return;
   }
   /* If the node to be deleted has two children */
   if(x->leftchild !=NULL && x->rightchild!=NULL)
   {
     parent=x;
     xsucc=x->rightchild;
     while(xsucc->leftchild != NULL)
     {
       parent=xsucc;
       xsucc=xsucc->leftchild;
     }
     x->data=xsucc->data;
     x=xsucc;
   }
   /* If the node to be deleted has no child */
   if(x->leftchild==NULL && x->rightchild==NULL)
   {
     if(parent->rightchild==x)
 parent->rightchild=NULL;
     else
 parent->rightchild=NULL;
     free(x);
     return;
   }
   /* If the node to be deleted has only right child */
   if(x->leftchild==NULL && x->rightchild !=NULL)
   {
     if(parent->leftchild==x)
       parent->leftchild=x->rightchild;
     else
       parent->rightchild=x->rightchild;
     free(x);
     return;
   }
   /* If the node to be deleted has only left child */
   if(x->leftchild != NULL && x->rightchild==NULL)
   {
     if(parent->leftchild==x)
       parent->leftchild=x->leftchild;
     else
       parent->rightchild=x->rightchild;
     free(x);
     return;
   }
}

/* Returns the address of the node to be deleted ,address of its parent and whether the node is found or not */
void search(struct btreenode **root,int num,struct btreenode **par,struct btreenode **x,int *found)
{
  struct btreenode *q;
  q=*root;
  *found=FALSE;
  *par=NULL;
  while(q!=NULL)
  {
     /* If the node to be deleted is found */
     if(q->data == num)
     {
       *found=TRUE;
       *x=q;
       return;
     }
     if(q->data==num)
     {
       *found=TRUE;
       *x=q;
       return;
     }
     *par=q;
     if(q->data > num)
 q=q->leftchild;
     else
 q=q->rightchild;
  }
}
/* Traverse a binary search tree in an LDR(Left-Data-Right) fashion */
void inorder(struct btreenode *sr)
{
   if(sr!=NULL)
   {
      inorder(sr->leftchild);
   /* Print the data of the node whose leftchild is NULL or the path has already been traversed */
   printf("%d\t",sr->data);
   inorder(sr->rightchild);
   }
}