find_leaves_of_binary_tree

Problem

Given a binary tree, find all leaves and then remove those leaves. Then repeat the previous steps until the tree is empty.

Example:
Given binary tree 
          1
         / \
        2   3
       / \ 
      4   5
Returns [4, 5, 3], [2], [1].

Explanation:

1. Remove the leaves [4, 5, 3] from the tree
                                    
  1
 / 
2

2. Remove the leaf [2] from the tree

1

3. Remove the leaf [1] from the tree
                                                                         
[]

Returns [4, 5, 3], [2], [1].