//This dummy head is awesome!!!! /** * Definition for binary tree with next pointer. * public class TreeLinkNode { * int val; * TreeLinkNode left, right, next; * TreeLinkNode(int x) { val = x; } * } */ public class Solution { public void connect(TreeLinkNode root) { TreeLinkNode dummy = new TreeLinkNode(0); TreeLinkNode pre = dummy; while(root!=null){ if(root.left!=null){ pre.next = root.left; pre = pre.next; } if(root.right!=null){ pre.next = root.right; pre = pre.next; } root = root.next; //dont forget!!! if(root == null){ root = dummy.next; pre = dummy; dummy.next = null; } } } }