I got a question that is flatten multilevel single linked list
similar to 430. Flatten a Multilevel Doubly Linked List, but There is NO prev pointer.
I firstly use BFS and Queue to solve this. But one interviewer tell me Queue may not solve this problem base on my idea. he let me use stack. Hopefully, I got it right.
Four interviewers, one asked about BQ, one asked coding, other two are shadow.