<p>Given the <code>root</code> of a binary tree, each node in the tree has a distinct value.</p>

<p>After deleting all nodes with a value in <code>to_delete</code>, we are left with a forest (a disjoint union of trees).</p>

<p>Return the roots of the trees in the remaining forest. You may return the result in any order.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2019/07/01/screen-shot-2019-07-01-at-53836-pm.png" style="width: 237px; height: 150px;" />
<pre>
<strong>Input:</strong> root = [1,2,3,4,5,6,7], to_delete = [3,5]
<strong>Output:</strong> [[1,2,null,4],[6],[7]]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> root = [1,2,4,null,3], to_delete = [3]
<strong>Output:</strong> [[1,2,4]]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the given tree is at most <code>1000</code>.</li>
	<li>Each node has a distinct value between <code>1</code> and <code>1000</code>.</li>
	<li><code>to_delete.length &lt;= 1000</code></li>
	<li><code>to_delete</code> contains distinct values between <code>1</code> and <code>1000</code>.</li>
</ul>

/**
 * 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:
    void visit(TreeNode* node,set<TreeNode*>&vis){
        if(node==NULL)
        return;
        vis.insert(node);
        visit(node->left, vis);
        visit(node->right, vis);
    }
    void solve(TreeNode* node,int l, map<int,pair<TreeNode*,TreeNode*>>&mpp, TreeNode* parent,  map<int,set<TreeNode*>>& level){
        if(node==NULL){
            return;
        }
        mpp[node->val].first=node;      
        mpp[node->val].second=parent;
        level[l].insert(node);
        solve(node->left,l+1,mpp,node,level);
        solve(node->right,l+1,mpp,node,level);
    }
    vector<TreeNode*> delNodes(TreeNode* root, vector<int>& to_delete) {
        set<TreeNode*>st;
        set<int>del;
        map<int,set<TreeNode*>>level;
        map<int,pair<TreeNode*,TreeNode*>>mpp;
        TreeNode* parent=NULL;
        solve(root,0,mpp,parent,level);
        for(int i=0;i<to_delete.size();i++){
            del.insert(to_delete[i]);     
            mpp[to_delete[i]].first->left=NULL; 
            mpp[to_delete[i]].first->right=NULL; 
            if(mpp[to_delete[i]].second!=NULL){
                if(mpp[to_delete[i]].second->left==mpp[to_delete[i]].first)
                mpp[to_delete[i]].second->left=NULL;
                else
                mpp[to_delete[i]].second->right=NULL;
            }
        }
        set<TreeNode*>vis;
        vector<TreeNode*>ans;
        for(auto i:level){
            for(auto j:i.second){
                if(vis.find(j)==vis.end() && del.find(j->val)==del.end()){
                    ans.push_back(j);
                    visit(j,vis);
                }
            }
        }
        return ans;
    }
};
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