public static void connectHelper2(TreeLinkNode root){
		if (root == null) return;
		if (root.left != null &&root.right != null) {
			TreeLinkNode rootLeft = root.right.left;
			TreeLinkNode rootRight = root.left.right;
			while (rootLeft != null && rootRight != null) {
				rootRight.next = rootLeft;
				rootRight = rootRight.right;
				rootLeft = rootLeft.left;
			}
			connectHelper2(root.left);
			connectHelper2(root.right);
		}
	}