public boolean insert(int key)
	{
		TreeNode pnode = parentHead;
		TreeNode node = pnode.left;
		while(node!=null) //left or right subtree
		{
			if(node.key>key)
			{
				pnode=node;
				node=node.left;
			}else if(node.key<key)
			{
				pnode=node;
				node=node.right;
			}else if(node.key==key)
				return false;
		}
		if(pnode.key>key)
			pnode.left=new TreeNode(key);
		else if(pnode.key<key)
			pnode.right=new TreeNode(key);
		else if(pnode.key==key) // duplicate values
		{
			return false;
		}
		return true;

	}