Reverse Level Order

Given a binary tree, return the reverse level order traversal of its nodes values. (i.e, from left to right and from last level to starting level).

1 <= number of nodes <= 5 * 10⁵

1 <= node value <= 10⁵

First and only argument is a pointer to the root node of the Binary Tree, A.

Return an integer array denoting the reverse level order traversal from left to right.

Input 1:

    3
   / \
  9  20
    /  \
   15   7

Input 2:

   1
  / \
 6   2
    /
   3

Output 1:

 [15, 7, 9, 20, 3] 

Output 2:

 [3, 6, 2, 1]

Explanation 1:

 Nodes as level 3 : [15, 7]
 Nodes at level 2: [9, 20]
 Nodes at level 1: [3]
 Reverse level order traversal will be: [15, 7, 9, 20, 3]

Explanation 2:

 Nodes as level 3 : [3]
 Nodes at level 2: [6, 2]
 Nodes at level 1: [1]
 Reverse level order traversal will be: [3, 6, 2, 1]