Given the root of a binary tree, each node in the tree has a distinct value.

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

Return the roots of the trees in the remaining forest.  You may return the result in any order.

Example 1:

Input: root = [1,2,3,4,5,6,7], to_delete = [3,5]
Output: [[1,2,null,4],[6],[7]]

Constraints:

• The number of nodes in the given tree is at most 1000.
• Each node has a distinct value between 1 and 1000.
• to_delete.length <= 1000
• to_delete contains distinct values between 1 and 1000.

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:    
    def delNodes(self, root, to_delete):
        """
        :type root: TreeNode
        :type to_delete: List[int]
        :rtype: List[TreeNode]
        """
        self.forests = []
        self.delete = to_delete
        
        node = self.divideAndConquer(root)
        
        if node:
            self.forests.append(node)
        
        return self.forests
    
    def divideAndConquer(self, node):
        
        if not node:
            return None
        
        left = self.divideAndConquer(node.left)
        right = self.divideAndConquer(node.right)
        
        if node.val not in self.delete:
            node.left = left
            node.right = right
            return node
        else:
            if left:
                self.forests.append(left)
            if right:
                self.forests.append(right)
                
            return None