【LeetCode 99】Recover Binary Search Tree

 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 
13     vector<TreeNode* > errs;
14     TreeNode *preNode;
15     
16     void rec(TreeNode *root)
17     {
18         if(root->left != 0)
19             rec(root->left);
20         
21         if(preNode != 0 && root->val < preNode->val)
22         {
23             errs.push_back(preNode);
24             errs.push_back(root);
25         }
26         
27         preNode = root;
28         
29         if(root->right != 0)
30             rec(root->right);
31     }
32     
33     void recoverTree(TreeNode* root) {
34         if(root == 0)
35             return ;
36         
37         preNode = 0;
38         
39         rec(root);
40         
41         int temp = 0, index = 1;
42         
43         if(errs.size() == 4)
44             index = 3;
45             
46         temp = errs[0]->val;
47         errs[0]->val = errs[index]->val;
48         errs[index]->val = temp;
49     }
50 };