二叉树的下一个结点

/*
public class TreeLinkNode {
    int val;
    TreeLinkNode left = null;
    TreeLinkNode right = null;
    TreeLinkNode next = null;

    TreeLinkNode(int val) {
        this.val = val;
    }
}
*/
public class Solution {
    public TreeLinkNode GetNext(TreeLinkNode node){
        if(node==null){
            return null;
        }
        if(node.right!=null){
            node=node.right;
            while(node.left!=null){
                node=node.left;
            }
            return node;
        }
        while(node.next!=null){
            TreeLinkNode root=node.next;
            if(root.left==node){
                return root;
            }
            node=node.next;
        }
        return null;
    }
}