Binary Tree Traversal Program in C

#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();
}

}

Posted in: C