private boolean sameTree(BinaryTreeNode a, BinaryTreeNode b) {
		
		if (a == null && b == null) {return true;}
		if (a != null && b != null) {			
			if (a.data == b.data) {
				boolean lst = sameTree(a.leftChild, b.leftChild);
				boolean rst = sameTree(a.rightChild, b.rightChild);
				return lst && rst;
			}			
		}
		
		return false;
	}