Print Binary Tree levels in sorted order | Set 2 (Using set)

Given a tree, print the level order traversal in sorted order.
Examples : 
 

Input :     7
         /    \
       6       5
      / \     / \
     4  3    2   1
Output : 
7
5 6
1 2 3 4

Print Binary Tree levels in sorted order  Set 2 (Using set): https://www.geeksforgeeks.org/print-binary-tree-levels-sorted-order-2/