<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
{
private:
    void processChilds(TreeNode* node, vector<TreeNode*>& forest)
    {
        if(nullptr != node->left)
        {
            forest.push_back(node->left);
        }
        if(nullptr != node->right)
        {
            forest.push_back(node->right);
        }        
    }
    bool delNode(TreeNode* root, const int to_delete, vector<TreeNode*>& forest)
    {
        if(nullptr != root->left && to_delete == root->left->val)
        {
            processChilds(root->left, forest);
            delete root->left;
            root->left = nullptr;
            return true;
        }
        else if(nullptr != root->right && to_delete == root->right->val)
        {
            processChilds(root->right, forest);
            delete root->right;
            root->right = nullptr;
            return true;
        }
        else
        {
            auto deleted = false;
            if(nullptr != root->left)
            {
                deleted = delNode(root->left, to_delete, forest);
            }
            if(!deleted && nullptr != root->right)
            {
                deleted = delNode(root->right, to_delete, forest);
            }
            return deleted;
        }
    }
public:
    vector<TreeNode*> delNodes(TreeNode* root, vector<int>& to_deletes)
    {
        vector<TreeNode*> forest;
        if(nullptr != root)
        {
            forest.push_back(root);
            for(const auto to_delete : to_deletes)
            {
                auto deleted = false;
                auto i = forest.begin();
                while(!deleted && forest.end() != i)
                {
                    auto node = *i;
                    if(to_delete == node->val)
                    {
                        forest.erase(i);
                        processChilds(node, forest);
                        deleted = true;
                    }
                    else
                    {
                        deleted = delNode(node, to_delete, forest);
                        ++i;
                    }

                }
            }
            
        }
        
        return forest;
    }
};
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