57 二叉树的下一个结点

public class Test57 {
    public TreeLinkNode GetNext(TreeLinkNode pNode) {
        if (pNode == null) {
            return null;
        }
        if (pNode.right != null) {
            pNode = pNode.right;
            while (pNode.left != null) {
                pNode = pNode.left;
            }
            return pNode;
        }
        TreeLinkNode par = pNode.next;
        while (par != null && par.left != pNode) {
            pNode = par;
            par = par.next;
        }
        return par;
    }
}

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

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