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 pNode)
    {
        if(pNode==null){
            return null;
        }
        if(pNode.right!=null){
            TreeLinkNode right=pNode.right;
            while(right.left!=null){
                right=right.left;
            }
            return right;
        }
        while(pNode.next!=null){
            TreeLinkNode pp=pNode.next;
            if(pp.left==pNode){
                return pp;
            }
            pNode=pp;
        }

        return null;
    }
}