I had a 1:1 on-campus interview. The recruiter asked me the following question:

"We have two sorted, single-direction linked lists. Write an efficient algorithm to merge them together so that the outcome is also sorted. Creating a new linked list is not allowed."

Then, they asked whether I was graduating the following quarter, to which I answered no.

After two weeks, I received an email stating that they could not proceed with the second round of interviews and could not provide a reason.

How would you merge two sorted linked lists without creating a new one, so that the outcome is sorted as well?