【剑指offer】二叉树的下一个结点

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

    TreeLinkNode(int val) {
        this.val = val;
    }
}

public TreeLinkNode GetNext(TreeLinkNode pNode) {
    if (pNode == null)
        return null;

    if (pNode.right != null) {
        pNode = pNode.right;

        while (pNode.left != null)
            pNode = pNode.left;
    }
    else {
        while (pNode.next != null && pNode.next.right == pNode)
            pNode = pNode.next;

        pNode = pNode.next;
    }

    return pNode;
}