Implementation of Binary Tree in C Programming

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

struct node
{
 int data;
 struct node *right, *left;
}*root,*p,*q;

struct node *make(int y)
{
 struct node *newnode;
 newnode=(struct node *)malloc(sizeof(struct node));
 newnode->data=y;
  newnode->right=newnode->left=NULL;
 return(newnode);
}

void left(struct node *r,int x)
{
 if(r->left!=NULL)
  printf("\n Invalid !");
 else
  r->left=make(x);
}

void right(struct node *r,int x)
{
 if(r->right!=NULL)
  printf("\n Invalid !");
 else
  r->right=make(x);
}


void inorder(struct node *r)
{
 if(r!=NULL)
 {
  inorder(r->left);
  printf("\t %d",r->data);
  inorder(r->right);
 }
}

void preorder(struct node *r)
{
 if(r!=NULL)
 {
  printf("\t %d",r->data);
  preorder(r->left);
  preorder(r->right);
}
}

void postorder(struct node *r)
{
 if(r!=NULL)
 {
  postorder(r->left);
  postorder(r->right);
  printf("\t %d",r->data);
 }
}

void main()
{

 int no;
 int choice;
 clrscr();
 printf("\n Enter the root:");
 scanf("%d",& no);
 root=make(no);
 p=root;

  while(1)
  {
   printf("\n Enter another number:");
   scanf("%d",& no);

   if(no==-1)
    break;
   p=root;
   q=root;

   while(no!=p->data && q!=NULL)
   {
    p=q;
    if(no < p->data)
     q=p->left;
    else
     q=p->right;
   }

   if(no < p->data)
   {
    printf("\n Left branch of %d is %d",p->data,no);
    left(p,no);
   }
   else
   {
    right(p,no);
    printf("\n Right Branch of %d is %d",p->data,no);
   }
  }
 
  while(1)
  {
   printf("\n 1.Inorder Traversal \n 2.Preorder Traversal \n 3.Postorder Traversal \n 4.Exit");
   printf("\n Enter choice:");
   scanf("%d",&choice);


   switch(choice)
   {
    case 1 :
     inorder(root);
     break;
    case 2 :
     preorder(root);
     break;
    case 3 :
     postorder(root);
     break;
    case 4 :exit(0);

    default:printf("Error ! Invalid Choice ");
     break;
   }
   getch();
  }

}

OUTPUT

 Enter the root:74

 Enter another number:71

 Left branch of 74 is 71
 Enter another number:12

 Left branch of 71 is 12
 Enter another number:72

 Right Branch of 71 is 72
 Enter another number:73

 Right Branch of 72 is 73
 Enter another number:100

 Right Branch of 74 is 100
 Enter another number:99

 Left branch of 100 is 99
 Enter another number:10

 Left branch of 12 is 10
 Enter another number:-1

 1.Inorder Traversal
 2.Preorder Traversal
 3.Postorder Traversal
 4.Exit
 Enter choice:1
         10      12      71      72      73      74      99      100
 1.Inorder Traversal
 2.Preorder Traversal
 3.Postorder Traversal
 4.Exit
 Enter choice:2
         74      71      12      10      72      73      100     99

 1.Inorder Traversal
 2.Preorder Traversal
 3.Postorder Traversal
 4.Exit
 Enter choice:3
         10      12      73      72      71      99      100     74