[剑指offer] 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 node = pNode.right;
            while(node.left != null){
                node = node.left;
            }
            return node;
        }
        while(pNode.next != null){
            TreeLinkNode root = pNode.next;
            if(pNode == root.left)
                return root;
            pNode = root;
        }
        return null;
    }
}