二叉搜索树与双向链表

/*
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
TreeNode(int x) :
val(x), left(NULL), right(NULL) {
}
};*/
class Solution {
public:
void link(TreeNode *root,TreeNode** last)
{
if(!root)
return ;
TreeNode* cur=root;
if(cur->left)
link(cur->left,last);
cur->left=*last;
if((*last)!=NULL)
(*last)->right=cur;
*last=cur;
if(cur->right)
link(cur->right,last);
}
TreeNode* Convert(TreeNode* pRootOfTree)
{
TreeNode * last=NULL;
link(pRootOfTree,&last);
while(last!=NULL&&last->left!=NULL)
last=last->left;
return last;
}
};