897. 递增顺序查找树

输入：[5,3,6,2,4,null,8,1,null,null,null,7,9]

       5
      /     3    6
   / \      2   4    8
 /        / \ 
1        7   9

输出：[1,null,2,null,3,null,4,null,5,null,6,null,7,null,8,null,9]

 1
     2
         3
             4
                 5
                     6
                         7
                             8
                                 9  

 1 /**
 2  * Definition for a binary tree node.
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     TreeNode* increasingBST(TreeNode* root) {
13         vector<int> vec;
14         inOrder(root,vec);
15         int size = vec.size();
16         TreeNode* p = root;
17       for(int i = 0;i<size;i++)
18       {
19         TreeNode*node = new TreeNode(vec[i]);
20         p->right = node;
21         p = p->right;
22       }
23       return root->right;
24           
25     }
26   void inOrder(TreeNode* root, vector<int>&vec)
27   {
28     if(root)
29     {
30       inOrder(root->left,vec);
31       vec.push_back(root->val);
32       inOrder(root->right,vec);
33     }
34   }
35 };