Print middle level of perfect binary tree without finding height

// Tree node definition 
class Node 
{ 
	public int key; 
	public Node left; 
	public Node right; 
	public Node(int val) 
	{ 
		this.left = null; 
		this.right = null; 
		this.key = val; 
	} 
} 

public class PrintMiddle 
{ 
	// Takes two parameters - same initially and 
	// calls recursively 
	private static void printMiddleLevelUtil(Node a, 
											Node b) 
	{ 
		// Base case e 
		if (a == null || b == null) 
			return; 

		// Fast pointer has reached the leaf so print 
		// value at slow pointer 
		if ((b.left == null) && (b.right == null)) 
		{ 
			System.out.print(a.key + " "); 
			return; 
		} 

		// Recursive call 
		// root.left.left and root.left.right will 
		// print same value 
		// root.right.left and root.right.right 
		// will print same value 
		// So we use any one of the condition 
		printMiddleLevelUtil(a.left, b.left.left); 
		printMiddleLevelUtil(a.right, b.left.left); 
	} 

	// Main printing method that take a Tree as input 
	public static void printMiddleLevel(Node node) 
	{ 
		printMiddleLevelUtil(node, node); 
	} 

	public static void main(String[] args) 
	{ 
		Node n1 = new Node(1); 
		Node n2 = new Node(2); 
		Node n3 = new Node(3); 
		Node n4 = new Node(4); 
		Node n5 = new Node(5); 
		Node n6 = new Node(6); 
		Node n7 = new Node(7); 

		n2.left = n4; 
		n2.right = n5; 
		n3.left = n6; 
		n3.right = n7; 
		n1.left = n2; 
		n1.right = n3; 

		printMiddleLevel(n1); 
	} 
}