输入一棵二叉搜索树，将该二叉搜索树转换成一个排序的双向链表。要求不能创建任何新的结点，只能调整树中结点指针的指向。

正确：

TreeNode pre = null;    public TreeNode Convert(TreeNode pRootOfTree) {        if (pRootOfTree == null)            return null;        Convert1(pRootOfTree);        TreeNode res = pRootOfTree;        while (res.left != null)            res = res.left;        return res;    }    public void Convert1(TreeNode pRootOfTree) {        if (pRootOfTree == null)            return;        Convert1(pRootOfTree.left);        System.out.print("1:");        System.out.println(pre == null ? "null" : pre.val);        // 记录链表中当前节点的前一个节点        pRootOfTree.left = pre;        if (pre != null)            pre.right = pRootOfTree;        pre = pRootOfTree;        System.out.print("2:");        System.out.println(pre == null ? "null" : pre.val);        Convert1(pRootOfTree.right);    }

错误：

public TreeNode Convert(TreeNode pRootOfTree) {        if (pRootOfTree == null)            return null;                TreeNode pre = null;        Convert(pRootOfTree, pre);        TreeNode res = pRootOfTree;        while (res.left != null)            res = res.left;        return res;    }    public void Convert(TreeNode pRootOfTree, TreeNode pre) {        if (pRootOfTree == null)            return;        Convert(pRootOfTree.left, pre);        System.out.print("1:");        System.out.println(pre == null ? "null" : pre.val);        // 记录链表中当前节点的前一个节点        pRootOfTree.left = pre;        if (pre != null)            pre.right = pRootOfTree;        pre = pRootOfTree;        System.out.print("2:");        System.out.println(pre == null ? "null" : pre.val);        Convert(pRootOfTree.right, pre);    }