LeetCode OJ：Recover Binary Search Tree（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(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     void recoverTree(TreeNode* root) {
13         vt.clear();
14         vi.clear();
15         if(!root) return;
16         tranverse(root);
17         sort(vi.begin(), vi.end());
18         for_each(vt.begin(), vt.end(), [this](TreeNode * t){static int i = 0; t->val = vi[i++];});
19     }
20 
21     void tranverse(TreeNode * root)
22     {
23         if(!root) return;
24         tranverse(root->left);
25         vt.push_back(root);
26         vi.push_back(root->val);
27         tranverse(root->right);
28     }
29 private:
30     vector<TreeNode *> vt;
31     vector<int> vi;
32 };

 1 class Solution {
 2 public:
 3     void recoverTree(TreeNode* root) 
 4     {
 5         p = q = prev = NULL;
 6         if(!root) return;
 7         tranverse(root);
 8         swap(p->val, q->val);
 9     }
10 
11     void tranverse(TreeNode * root)
12     {
13         if(!root) return ;
14         tranverse(root->left);
15         if(prev && (prev->val > root->val)){
16             if(!p) p = prev;//这里应该注意
17             q = root;//注意为什么q取的是root
18         }
19         prev = root;
20         tranverse(root->right);
21     }
22 private:
23     TreeNode * p, * q;
24     TreeNode * prev;
25 };