【树】99. 恢复二叉搜索树

 1 /**
 2  * Definition for a binary tree node.
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 8  *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 9  *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
10  * };
11  */
12 class Solution {
13 public:
14     void recoverTree(TreeNode *root)
15     {
16         TreeNode* first=NULL;
17         TreeNode* second=NULL;
18         TreeNode* prv=NULL;
19 
20         treeWalk(root,prv,first,second);
21 
22         //change
23         int tmp=first->val;
24         first->val=second->val;
25         second->val=tmp;
26     }
27 
28     void treeWalk(TreeNode* root, TreeNode*& prv, TreeNode*& first, TreeNode*& second)
29     {
30         if(root==NULL)
31         {
32             return;
33         }
34         treeWalk(root->left,prv,first,second);
35 
36         if( (prv != NULL) && (prv->val > root->val) )
37         {
38             if(first == NULL)
39             {
40                 first = prv;
41             }
42             second = root;
43         }
44         prv=root;
45 
46         treeWalk(root->right,prv,first,second);
47     }
48 };