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;
        root.next = null;
        nodeConnect(root.left, root.right);
    }
    
    public static void nodeConnect(TreeLinkNode left, TreeLinkNode right) {
        if (left == null) return;
        left.next = right;
        right.next = null;
        nodeConnect(left.left, left.right);
        nodeConnect(left.right, right.left);
        nodeConnect(right.left, right.right);
    }
}