Print Binary Tree levels in sorted order

Given a Binary tree, the task is to print its all level in sorted order

Examples:

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

Input :     7
          /    \
        16       1
       / \      
      4   13    
Output :
7 
1 16
4 13

Here we can use two Priority queue for print in sorted order. We create an empty queue q and two priority queues, current_level and next_level. We use NULL as a separator between two levels. Whenever we encounter NULL in normal level order traversal, we swap current_level and next_level.

Output:

Level Order traversal of binary tree is 
7 
5 6 
1 2 3 4