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    vector<TreeNode*> vet;
14     TreeNode* KthNode(TreeNode* pRoot, int k)
15     {
16         midsearch(pRoot);
17         if (k<1 || k>vet.size())
18             return NULL;
19         else
20         {
21             return vet[k - 1];
22         }
23     }
24     void midsearch(TreeNode * root)
25     {
26 
27         if (root == NULL)
28             return;
29         if (root != NULL)
30         {
31             midsearch(root->left);
32             vet.push_back(root);
33             midsearch(root->right);
34         }
35     }
36     
37 };