LeetCode 116. Populating Next Right Pointers in Each Node

/**
 * 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) {
    	if (root == null) return;
        TreeLinkNode pre = root;
    	TreeLinkNode cur = null;
    	while (pre.left != null) {
    		cur = pre;
    		while (cur != null) {
    			cur.left.next = cur.right;
    			if (cur.next != null) cur.right.next = cur.next.left;
    			cur = cur.next;
    		}
    		pre = pre.left;
    	}
    }
}