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。

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    public TreeNode Convert(TreeNode pRootOfTree) {
        if(pRootOfTree==null){
            return null;
        }
        if(pRootOfTree.left==null && pRootOfTree.right==null){
            return pRootOfTree;
        }
        //左子树
        TreeNode leftNode = Convert(pRootOfTree.left);//
        TreeNode p = leftNode;
        while(p!=null && p.right!=null ){
            p = p.right;
        }
        if(leftNode!=null){
            p.right = pRootOfTree;
            pRootOfTree.left = p;
        }
        
        TreeNode rightNode = Convert(pRootOfTree.right);
        if(rightNode!=null){
            rightNode.left = pRootOfTree;
            pRootOfTree.right = rightNode;
        }
        
        
        leftNode=leftNode!=null?leftNode:pRootOfTree;
        return leftNode;
    }        
}