二叉搜索树的第k个节点

 1 /*
 2 struct TreeNode {
 3     int val;
 4     struct TreeNode *left;
 5     struct TreeNode *right;
 6     TreeNode(int x) :
 7             val(x), left(NULL), right(NULL) {
 8     }
 9 };
10 */
11 class Solution {
12 public:
13     void DFS(TreeNode *pRoot, int &k, TreeNode **pres)
14     {
15         if(pRoot->left && k)DFS(pRoot->left, k, pres);
16         --k;
17         if(k==0)
18         {
19             *pres=pRoot;
20             return;
21         }
22         if(pRoot->right && k)DFS(pRoot->right, k, pres);
23     }
24     TreeNode* KthNode(TreeNode* pRoot, int k)
25     {
26         if(pRoot==NULL || k<=0)return NULL;
27         TreeNode *res=NULL;
28         DFS(pRoot, k, &res);
29         return res;
30     }
31 
32     
33 };