leetcode

0 class Solution {

1 public:

2 void recoverTree(TreeNode *root) {

3 stack<TreeNode *> st;

4 TreeNode *head = root, *prev = new TreeNode(INT_MIN), *l1 = nullptr, *l2 = nullptr;

5 while (true) {

6 while (root) {

7 st.push(root);

8 root = root->left;

9 }

10 if (st.empty()) break;

11 root = st.top(), st.pop();

12 if (root->val < prev->val) {

13 if (!l1) l1 = prev;

14 l2 = root;

15 }

16 prev = root;

17 root = root->right;

18 }

19 swap(l1->val, l2->val);

20 }

21 };