第十八周 6.27 --- 7.3

 1 class Solution{
 2 public:
 3     TreeNode* p1;
 4     TreeNode* p2;
 5     TreeNode* pre;
 6     void recoverTree(TreeNode* root){
 7         inorder(root);
 8         if(p1 != NULL && p2 != NULL){
 9             swap(p1->val,p2->val);
10         }
11     }
12 
13     void inorder(TreeNode* root){
14         if(root == NULL) return;
15         if(root->left != NULL) inorder(root->left);
16         if(pre != NULL && pre->val > root->val){
17             if(p1 == NULL){
18                 p1 = pre;
19                 p2 = root;
20             }
21             else p2 = root;
22         }
23         pre = root;
24         if(root->right != NULL) inorder(root->right);
25     }
26 };