leetcode

0 class Solution {

1 public:

2 TreeNode *pruneTree(TreeNode *root) {

3 TreeNode dummy(1, root, nullptr);

4 unordered_set<TreeNode *> has;

5 stack<TreeNode *> st;

6 st.push(&dummy);

7 while (!st.empty()) {

8 TreeNode *root = st.top();

9 if (!root) {

10 st.pop();

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

12 if (has.count(root->left))

13 has.insert(root);

14 else

15 root->left = nullptr;

16

17 if (has.count(root->right))

18 has.insert(root);

19 else

20 root->right = nullptr;

21

22 if (root->val == 1) has.insert(root);

23 continue;

24 }

25 st.push(nullptr);

26 if (root->left) st.push(root->left);

27 if (root->right) st.push(root->right);

28 }

29 return dummy.left;

30 }

31 };