Why it is raising exception 🤔

Question

https://code.sololearn.com/cWoUz8F09aKy/?ref=app

Answer 1

I changed line 17 to
head=newnode;

And it prints.

Answer 2

Happy I could help!
Enjoy your coding!

Answer 3

Ausgrindtube the first element inserted into queue must be it's head as well as tail. Thanks a lot for clarifying my doubt.