First Round Telephone interview

I had a technical phone interview and this was the first round in it. I am not disclosing the name since, I am still in the middle of the interview process. The interviewer asked me to briefly tell about myself. Before I could say 3 or 4 lines he cut me short and asked what was my role as a student programmer at Ohio Medical Center. Since my resume had C, C++, Java and C# he asked which languages I was most comfortable with and asked me to rate myself on a scale of 1-10.

Then he asked questions on OOPs concepts. He asked quite a lot of them and since I was answering pretty quickly he went on asking them. He asked questions on design patterns and asked about Singleton, Observer, Strategy, Factory, Composite. I did not know what Composite pattern was so could not answer it. Also asked me to elaborate on differences between C++ and Java, parameter passing types, auto-boxing in java. Also asked lot of questions on Collections in Java. Hash table, hashmap, vector, arraylist. I dont remember other questions but we spoke about 15 min on Java/C#.

Then he asked about data structures, stacks, queues. hashing, linked lists. The questions on linked lists were to find the 5th node from the last. This is popular question so I am not answering it here. Other question was to find if there is a loop in the linked list. I answered using Tortoise and Hare problem and we had discussion about why the method works. Again this is popular question, so you can find it on web.

The next question was to find the repeating element in an array where only one element is repeating and all are unique. The question was modified to find the element repeating thrice where are all other elements are unique and one element is repeating twice. I used hashtable approach for both the questions.

Then came the final decider question for which we need to write the code and send. He asked me to design an multi elevator system in a building and send the code in Java by evening. Since I had lot of time, it had to be quite exhaustive. I submitted the code but afterward, I was not happy with the design. May be I should have used a different approach. I used elevatorchallenge.com as reference but I did not copy that.

The interviewer said that I did very well in the interview but I have to see if he would like the elevator system code. Waiting to hear back from them.