all-nodes-distance-k-in-binary-tree

Given the root of a binary tree, the value of a target node target, and an integer k, return an array of the values of all nodes that have a distance k from the target node.

You can return the answer in any order.

Example 1:

Input: root = [3,5,1,6,2,0,8,null,null,7,4], target = 5, k = 2
Output: [7,4,1]
Explanation: The nodes that are a distance 2 from the target node (with value 5) have values 7, 4, and 1.

Example 2:

Input: root = [1], target = 1, k = 3
Output: []

Constraints:

• The number of nodes in the tree is in the range [1, 500].


• 0 <= Node.val <= 500


• All the values Node.val are unique.


• target is the value of one of the nodes in the tree.


• 0 <= k <= 1000