Deutsche Bank interview questions

Consultant forwarded my resume to the Company and it got shortlisted. The initial round was telephone - It was more of get to know the job profile and whether I fit the job role or not. Got a call from the HR asking me to come for the further rounds. When I met the technical interview person, looked like he was busy with his work and asked me to write code for singleton design pattern. When I wrote and showed it to him, he asked me to write the code that I implemented in my project. I was like shocked and surprised, it takes days to implement the requirement that I did in my project. I asked him to provide more details or the requirement only then I will be able to write the code. Then he asked me write complete code for single linked list. When I was explaining him while I was coding, he stopped from explaining it to him and finish off the code. I took around 10 min to code completely. Did a small mistake when trying to introduce circular linked list and was politely thrown out saying HR will get back to me.