Polymorphism - recruitment questions

Hello!

I think it's time to get back to a bit more technical topics. Today I would like to talk about polymorphism recruitment questions. I my opinion, this is a very important element of any job interview as a C++ developer. We may have trouble answering other questions, but here in the case of polymorphism, we need to demonstrate a very good understanding of the subject. Typically, questions related to this topic are theoretical and practical in nature. Below are some questions I encountered:

• What is polymorphism? - Such a question may be asked at the phone screening stage.
• Can you give an example? - This question also came up at the phone screening stage. It was necessary to present simple hierarchy of classes.
• Questions about vptr and vtable - It is also very important topic and appears in virtually every job interview. Some argue that this is a bit more advanced and difficult to understand. Perhaps it is so, but if we have good study materials, we should catch the topic.
• Diamond problem - It's also a classic. Usually there is a question about how to solve this problem.
• Code snippets - I encountered various things here. Usually it is to check what will be the result of calling the method. You need to demonstrate your understanding of how polymorphism works in practice. You need to pay attention to whether it is enabled by the key word virtual, whether a virtual destructor is defined etc.

I think these questions above are such classics. We will answer the first two today. I will devote a separate post to questions related to snippets, vptr, vtable and the diamond problem.

The first question was about the definition of polymorphism. I must admit that during my first recruitment interviews, it was difficult for me to answer this question. The more I understood object-oriented programming, the answer was more and more natural to me. I think with a clear conscience we can answer in this way and it will be the answer accepted by the recruiter:

The second question was to give an example of polymorphism on the example of class hierarchy. I was asked about this during a phone interview. My verbal answer was based on the following example:

I described in words what you can see, i.e. the base class "Animal" with one virtual method "animalSound". Two classes that inherit from it and create their own implementations of this method. It is also important to discuss the lines between 38 and 40 after the reassignment to the base class type pointer.

I think that would be enough for today. In the next post, I will present some snippets that you can come across at a job interview.