Delete Nodes And Return Forest

Description

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.

Solution(javascript)

const delNodes = function (root, to_delete = []) {
  const map = new Map()
  const toDeleteSet = new Set(to_delete)
  const aux = (node, currentRoot) => {
    if (!node) {
      map.set(currentRoot, currentRoot)
      return null
    }
    const { val } = node
    if (toDeleteSet.has(val)) {
      if (node.left) {
        aux(node.left, node.left)
      }
      if (node.right) {
        aux(node.right, node.right)
      }
      if (node !== currentRoot) {
        map.set(currentRoot, currentRoot)
      }
      return null
    }
    node.left = aux(node.left, currentRoot)
    node.right = aux(node.right, currentRoot)
    return node
  }
  aux(root, root)
  return [...map.values()]
}