Binary Tree

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


struct btree
{
int data;
struct btree * right;
struct btree * left;
};


struct btree * head = NULL;


struct btree * getNode(int data)
{
struct btree * temp =NULL;
temp = (struct btree*)malloc( sizeof(struct btree) );
temp -> left = NULL;
temp -> right = NULL;
        temp -> data = data ;
printf("\n getNode :: temp -> data = %d", temp -> data );
return temp;

}

struct btree * insert(struct btree * root, int data)
{

if ( root == NULL )
{
head = getNode(data);
return  head ;
}
else
{
printf("\n insert:: root is not null");

if ( data <= ( (root) -> data ) )
{
printf("\n  LESS THAN ");
root -> left = insert(  ( (root) -> left ), data ) ;
}
if ( data > ( (root) -> data ) )
{
printf("\n  MORE THAN ");
root -> right =  insert( ( (root) ->right ) , data  ) ;
}
return root ;
}
}


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

}


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

}

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

int main()
{
struct btree * root = NULL;
printf("\n In main ");

printf("\n  main: Adding nodes ");
root = insert(head, 9) ;

root = insert(root, 4);
root = insert(root, 15);
root = insert(root, 6);
root = insert(root, 12);
root = insert(root, 17);
root = insert(root, 2);

printf("\n main:: nodes added ");

printf("\n main:: root -> data  = %d", root  -> data);
printf("\n main:: Pre order display");
printf("\n main:: head -> data  = %d", head -> data);
printf("\n ");
preorder( root );

printf("\n");

printf("\n Inorder display");
inorder( root );


printf("\n");
printf("\n post order display");
postorder( root );


return 0;
}