Delete Nodes And Return Forest
Difficulty: Medium
Category: DSA
Topics: Array, Hash Table, Tree, Depth-First Search, Binary Tree
Asked at: Google, Amazon, Facebook, Salesforce
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]]
```
**Example 2:**
**Input:** root = [1,2,4,null,3], to_delete = [3]
**Output:** [[1,2,4]]
```
**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`.