The 10 C++ Programming Questions to Expect in an Interview

July 27, 2021
8
min read
The 10 C++ Programming Questions to Expect in an Interview
Ana Gospodinova
by
Ana Gospodinova

If you are a c++ programmer, then you know how important it is to be prepared for job interviews.

Knowing the right questions and answers can make or break your chances of getting the position.

Below are some of the most common interview questions asked in c++ programming interviews and their answers.

What is the c++ string class?

The std::string is a templatized container for character strings. It supports basic operations such as: concatenation, comparison and iterators. The most common implementation of this template in C++11 and onward is called std::basic_string or just "basic_string".

What is the difference between a c++ string and an std::string?

The simple answer would be that both are containers for character strings. The main difference is in how they're implemented. A std::basic_string represents its content using a vector of characters, while a c++ string holds them inside themselves as part of the string object.

What are the advantages of using c++ strings over std::strings?

The main advantage is in how they're implemented: a vector of characters vs an internal representation. This means that when you use a c++ string, if someone has to copy it or change its content, he/she will only have to make a deep copy of the string, while with std::string you will need to make a full copy.

Explain what is meant by 'scope resolution operator' or ::?

The scope resolution operator allows access to names that are declared in an outer block without having to explicitly specify their namespace. For example: if we have some code like

int outer_var = 123;

namespace ns { int inner_var = 999; }

then, the scope resolution operator allows us to access outer_var without having to specify its namespace: ::outer::inner. In this example, we would be referring to "ns::inner". There are two other forms of the scope resolution operator:

- ::begin - refers to the namespace directly above the current level, or equivalently @namespace in XAML.

- ::end - refers to the namespace that is below this one, or equivalently ns::ns_var in C++ and "ns" : "inner" in XML.

What is encapsulation?

Encapsulation is the process of containing or bundling data and functions together into a single unit. It's important because it prevents access to data that may not be intended for public use, while still allowing other code outside the object itself to interact with those same functions. The benefit of this can be seen in the following example:

class myClass { public string name; int age = 31; }

If you want to access the data of an object, all you have to do is create a pointer or reference variable and assign it with the address of that class. This will give us read-write access to those variables as well. But if you're not careful, you might end up modifying the variables that are private.

What is meant by 'private' and public in c++?

Public functions or members can be accessed from anywhere within a program; whereas, private ones cannot. So when declaring an identifier as "private" it ensures that only other identifiers of the same type, in the same class or namespace, can access it.

What is virtuality?

Virtual methods are ones that only exist as a placeholder for derived classes to override; they're called "virtual" because they contain at least one function call to another virtual method and all functions from which these calls originate must also be declared with the keyword "virtual" in the base class.

What is a virtual function?

A virtual function is one with a declaration in its class that includes the keyword "virtual." When you include this keyword, several things happen. First of all, when derived classes are created from an original base class containing a virtual method, each must also contain at least one function with the same signature as that of the virtual method in its base class. Secondly, when an object is allocated from a derived class and a function call to one of those virtual methods is made on it, this could be overridden by any other function with the same name inside another derived class - even if that functions resides within some third party code or library.

What is refactoring?

Refactoring is a process of modifying code to improve its readability, maintainability and reusability without changing functionality or behavior. It's not easy but it really pays off when you do need to chanfe something and you can't because the code is in a bad shape.

What is the difference between a c++ string and an std::string?

The main difference is in how they're implemented: a vector of characters vs an internal representation. This means that when you use a c++ string, if someone when you use a c++ string, if someone has to copy it or change its content, he/she will only have to make a deep copy of the string, while with std::string you will need to make a full copy.

How can you improve the code?

There are a few ways to refactor c++ code. One way is using "extract method" which will extract part of your c++ code, sort of like a c++ function, and put it in another place. It's a good way to organize your c++ code and make it more readable.

Apart from coding questions you are usually asked to reveal more about yourself during an interview. So it is good if you prepare answers to the following questions:

- What are your strengths and weaknesses?

- How would you describe yourself as an employee?

- Why should we hire you?

- When have you had to take responsibility for a project that was not working out satisfactorily or when things went wrong in the company, what did you do about it?

- Tell me about your management style?

- How would you deal with a colleague who is not pulling their weight or one that doesn't get along well with others in the office?

- What are your expectations about this position and what do you see as its challenges and opportunities for growth?

- Why should I hire you over someone else, like somebody else in this company?

- What do you think are your key strengths and weaknesses relative to the position I am looking for?

- How would you describe yourself as an employee?

To be prepared for a job interview as a C++ developer you should also consider these 6 tips:

- Prepare an answer for the job that you're about to apply in terms with your experience, why you are qualified and what is beneficial for this company?

- Practice answering these questions with a friend or someone else who will ask them from time to time so it doesn't seem like it is your first time.

- Prepare for the interview by researching about this company and if possible know some of their competitors in order to show interest on what they do.

- Do not leave any question unanswered, but try to answer them as briefly as you can because nobody likes long answers that go nowhere or are too vague.

- Prepare a list of questions to ask the interviewer when it is your turn, but make sure they are not too personal or offensive such as "How much do you earn?"

- Research about this company and if possible know some of their competitors in order to show interest on what they do.

If you get asked to do a coding test during the interview try to be prepared for it. Here are some c++ coding test questions you will most likely come across during an interview:

- Write a program that calculates the total sum of all numbers in a given list

int main() { int counter = 0; while (!cin) { cout<<"Please enter input:" <<endl; char input; cin >> input; if (cin.eof()) break; counter++; } cout<<"Input entered: " <<endl

cout<<"Sum of the numbers in a list is: " <<counter

return 0;}

- Calculate and print the sum of all integers from n to m, inclusive, using a loop

int main() { int sum = 0; for (int n=0, m=1000000 ; n <= m ; ++n)

sum += n;}

- Write a function that will return the average of five numbers entered by the user. The function should take an array as input and output the result to the screen

int main() { int input[ ] ={0, 0, 0, 0}; cout<<"Please enter five numbers:" <<endl; cin >> input ;

cin.get(); return (input[0] + input[i])/n;}

- Write a program to calculate the square root of an integer

int main() { float input; cin >> input ;

return sqrt(input);}

- Write a program to calculate the factorial of an integer. The factorial is calculated by multiplying consecutive integers, starting with one and ending at n. For example, the factorial of four would be: (one*two*three*four)

int main() {

return (n)*(factorial(n-i));}

With this information at hand you should be well prepared for your job interview as a C++ developer.

If you are looking for a job and want to work on some of fast growing startups or future-proof and established businesses then check out our jobs for C++ developer.

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