/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    vector<TreeNode*> ret;
    set<int> s;
    void Ord(TreeNode* root) {
        if (!root) return;
        if (s.find(root->val) != s.end()) {
            root->val = 0;
            if (root->left) ret.push_back(root->left);
            if (root->right) ret.push_back(root->right);
        }
        Ord(root->left);
        Ord(root->right);
    }
    void Del(TreeNode* root) {
        if (!root) return;
        auto t1 = root->left;
        auto t2 = root->right;
        if (t1 && !t1->val) root->left = nullptr;
        if (t2 && !t2->val) root->right = nullptr;
        Del(t1);
        Del(t2);
    }
    void delVector() {
        for (int i = 0; i < ret.size(); ) {
            if (ret[i] && !ret[i]->val)
                ret.erase(ret.begin() + i);
            else i++;
        }
    }
    vector<TreeNode*> delNodes(TreeNode* root, vector<int>& to_delete) {
        int len = to_delete.size();
        if (!root) return ret;
        ret.push_back(root);
        if (!len) return ret;
        s = set<int>(to_delete.begin(), to_delete.end());
        Ord(root);
        Del(root);
        delVector();
        return ret;
    }
};