Level order traversal in spiral form | Using one stack and one queue

Write a function to print spiral order traversal of a tree. For below tree, function should print 1, 2, 3, 4, 5, 6, 7. 
 

👁 Spiral image

You are allowed to use only one stack.

We have seen recursive and iterative solutions using two stacks . In this post, a solution with one stack and one queue is discussed. The idea is to keep on entering nodes like normal level order traversal, but during printing, in alternative turns push them onto the stack and print them, and in other traversals, just print them the way they are present in the queue.

Following is the implementation of the idea.  

1 2 3 4 5 6 7 

Complexity Analysis:

• Time Complexity : O(n) 
• Auxiliary Space : O(n)