Top 40 C++ Interview Questions and Answers

C++ is one of the most popular Object-Oriented Programming languages used by developers to design and build software and applications. C++ interview questions are asked extensively in technical interviews at FAANG and Tier-1 companies. The language goes way back to 1985, when it was first introduced, and can still perform advanced programming tasks.

If you are preparing for your upcoming technical interview and want to use C++ as your choice of programming language, knowing answers to the commonly asked C++ interview questions is essential. Questions asked at C++ interviews can be around programming theory and coding problems on Data Structures and Algorithms. So in this article, we’ll look at C++ interview questions and answers on programming theory, C++ coding interview questions, basic and C++ interview questions, and more.

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Let’s go ahead and look at some popular C++ interview questions and answers for freshers and experienced developers to help you prepare for your upcoming interview.

Here’s what we’ll discuss:

• Difference between C and C++
• Most Popular C++ Interview Questions
• C++ Coding Interview Questions
• How to Prepare for C++ Interviews
• FAQs on C++ Interview Questions

Difference Between C and C++

This is a common C++ interview question asked at software developer interviews. Both C and C++ have similar Syntaxes and code structures, but C++ allows developers to perform more advanced tasks and build comprehensive software programs. While C is a Procedural Oriented Programming Language, C++ is an Object-Oriented Programming Language, thereby incorporating more advanced features. C++ is essentially a superset of C and was developed to address the limitations of C.

Let’s quickly look at the main differences between both these languages.

Most Popular C++ Interview Questions Asked in Tech Interviews

In this section, we’ll look at some common and popularly asked C++ interview questions that you can expect at your next technical interview.

Basic C++ Interview Questions

Q1. What is a Class in C++?

A Class in C++ is a data type defined by the user. It is a fundamental data type in C++ that defines the behavior and attributes of the entity.

Q2. Define and Object in C++

An Object in C++ is an instance of a class. It is an entity that exhibits behavior and state, defined by the Class that it is part of.

Q3. What are the various data types available in C++?

There are four different data types in C++. They are:

• Enumeration. E.g., enum
• Primitive Datatype(basic datatype). E.g., float, char, short, int, long, bool, double, etc.
• User-defined data types. E.g., structure, union, class, etc.
• Derived datatype. E.g., pointer, array, reference, pointers, etc.

Q4. What are some advantages of using C++ to build software programs and applications?

This is a popular C++ interview question asked in software engineer interviews. The advantages of C++ are:

• The programming language is general-purpose and can perform various functions and activities.
• Code developed using C++ can be used in any platform and OS.
• C++ comprises an extensive library of functions that help perform a wide array of tasks.
• C++ allows for data hiding, a feature that enables programmers to secure data and programs.

Q5. What concepts of OPPs does C++ exhibit?

This is another popular C++ interview question asked at software engineering interviews. C++ is fundamentally Object-Oriented Programming (OOP). The OOP concepts that C++ exhibits include are:

• Objects
• Classes
• Inheritance
• Polymorphism
• Encapsulation
• Abstraction
• Data Binding

Q6. What do you understand by Inheritance in C++?

Inheritance is a feature in C++ that allows the reusability of functions in a class, thereby preventing code redundancy. It is a core feature of the Object-Oriented Programming model. Through inheritance, a new class is enabled to inherit the characteristics of an older class. When this happens, the new class is called the Derived Class, while the new class is called the Base class.

Q7. What is encapsulation in C++?

This is a standard C++ interview question in C++ software developer interviews and FAANG+ software engineer interviews. Encapsulation is a core feature in C++ that binds the data members and functions in a single unit. Data and information within the class are wrapped and made visible when a request is sent. External methods are prevented from accessing the data within the class through encapsulation.

Q8. What is abstraction in C++?

Abstraction is a core feature in C++ that allows developers only to show the required details while hiding the details on the implementation. If the members of a class are public, they are visible and accessible by external methods and functions.

Q9. Explain Polymorphism in C++

Polymorphism is a feature in which multiple functions have the same definition but can perform different functionalities. Static polymorphism and dynamic polymorphism are the two types of polymorphism in C++.

Q10. State the basis by which Method Overloading can be performed in C++?

In C++, method overloading is a technique through which multiple functions can have the same name but perform different actions. Method overloading in C++ is dependent on the following aspects:

• The number of parameters that are used to pass the function
• The different types of parameters that are passed
• The return type of the function

Q11. What do you understand about Namespace in C++?

A namespace is a provision in C++ to prevent naming conflicts while running batches of code. Namespace removes the ambiguity in task execution, where different tasks can sometimes run with the same name.

C++ has a standard Namespace called “std,” and various classes, functions, and methods are contained within the Namespace.

Q12. What is the difference between the commands delete and delete[]

The difference between delete and delete[] commands in C++ is that delete is used to remove a unit of memory in a class, delete[] is used to remove an entire array.

Advanced C++ Interview Questions

Q13. What are access specifiers in C++

This gain is a common C++ interview question asked in developer interviews. Access specifiers in C++ declare how functions and class variables contained within a class are accessed. There are three fundamental access specifiers in C++. They are:

• Private: In this type of access specifier, functions and variables can only be accessed by methods within the class.
• Public: In this type of access specifier, functions and variables can be accessed by outside classes.
• Protected: In this type, the child class can only access variables and functions, which is a subset of the parent class. This type of class is relevant while employing the concept of inheritance in OOP.

Q14. Name the ways by which you can export a function from DLL

You can export a function from DLL by:

• Taking a function reference from the DLL instance
• Employing DLL’s Type Library

Q15. What is a friend function in C++?

A friend function in C++ is a function type that behaves as a friend of a given class and can access the protected and private members (functions and variables) of the class. A friend function isn’t a member of the class in question, but it needs to be specified in the class definition.

Q16. What are some characteristics of the friend function in C++?

This is another common C++ interview question asked in technical interviews. Some characteristics of the friend function include:

• It uses objects in the class as arguments.
• Friend functions cannot be called by objects within the class, as these functions aren’t contained within the class.
• The friend function cannot directly access private members of a class. The function has to use the object name and a dot operator every time a member from the class needs to be accessed.

Q17. What is Data Binding in C++ and OPP models?

Data Binding is a core feature in C++  that allows developers to bind the business logic and application UI. If any changes are made to the program’s business logic, the same will reflect in the application UI.

Q18. What is the fundamental difference between arrays and lists in the OOP model?

Arrays and lists are common data types used in Object-Oriented Programming to build software programs and applications. The fundamental difference between the two Arrays is a collection of homogeneous elements, while lists are a collection of heterogeneous elements.

Additionally, the memory allocation for arrays is continuous and static, while the memory allocation for lists is random and dynamic.

Q19. What is a Virtual Function in C++?

A Virtual Function in C++ is fundamentally a member function present in the base class and defined by the derived class. When a function in C++ is virtual, the program decides when the function must be called, depending on the type of the object pointed by the base pointer. C++ can execute different versions of a virtual function.

Q20. What are some rules to be followed when working with virtual functions in C++?

• A virtual function can be a friend function of another class
• Virtual functions cannot be static members of the class
• Virtual functions need to be members of the same class and need to be contained within the class
• These functions are called by using Object Pointers

Q21. What is overloading in C++? What are the types of overloading in C++?

This is another common C++ interview question asked in technical interviews. Overloading in C++ is when a particular object of a class exhibits multiple behavioral features. The object, during overloading, returns different versions of the function.

The two types of overloading are Function Overloading and Operator Overloading.

Q22. Is it possible to have a recursive inline function in C++?

While it is possible to call an inline function in C++, the compiler won’t generate the code without a good optimizer. That way, you’re able to execute both recursive and non-recursive functions depending on the depth of recursion.

Q23. What is the function of the “this” pointer in C++?

This again is one of the most popular C++ interview questions asked at technical interviews. The “this” pointer contains the memory address of the given object. Passed in the form of a hidden argument, the “this” pointer is a constant pointer available as a local variable in the body of nonstatic functions.

Q24. What is the difference between Function Overloading and Operator Overloading?

Operator Overloading is a feature that allows developers to redefine the way an operator functions for user-defined data types. Function Overloading is a feature that enables different functions that exhibit different parameters and behaviors to possess the same name.

Q25. What is a destructor in C++?

Another popular C++ interview question asked at technical interviews pertains to destructors and constructors. In C++, destructors are member functions within the class and possess the same name as the class. Destructors are exhibited automatically when objects lose their scope.

Q26. What is a constructor in C++?

Constructors are special member functions within a class that doesn’t have return types. They are used to initialize new objects of a class. Constructors in C++ are called automatically when objects are created in a class.

Q27.  What do you understand about Static members in C++?

Static member functions and static member data are contained within a class and must be declared. When a function is declared static, only a single copy of the data is maintained for the class. Static functions in the class don’t contain the “this” pointer.

Q28. What is a pure virtual function in C++?

In C++, a pure virtual function does not have a formal definition in a class. Pure virtual functions in C++ are succeeded by a “0”.

Q29. What is the function of the Scope Resolution operator in C++?

Scope Resolution operators, specified by the symbol - (::), are fundamentally used to define member functions outside of the class. They come into use when creating protected and private classes in C++.

Q30. What do you mean by class templates in C++?

This again is one of the most common C++ interview questions asked at software developer interviews. Class templates are generally used while creating a family of classes and functions. For instance, while creating an array class, you can create a template to help create various array types such as float, int, etc. Similarly, you can create function templates to define similar functions.

The above C++ interview questions and answers will give you a fair understanding of the concepts that feature in C++ developer and software engineer interviews.

C++ Coding Interview Questions for Technical Interviews

In technical interviews, you will have to attempt coding interview questions around core data structures and algorithms. In fact, in the technical Phone Screen and On-site rounds of tech interviews, your problem-solving skills are tested through the extent of your knowledge and understanding of concepts in core data structures and algorithms.

In this section, we’ll look at some sample C++ coding interview questions asked at FAANG+ interviews.

Before that, here are the topics that are important from the perspective of the interview:

• Arrays, strings, and linked lists
• Sorting algorithms — quicksort, merge sort, heap sort, etc.
• Hash tables and queues
• Recursion
• Trees and graphs
• Graph algorithms, including greedy algorithms
• Dynamic programming

Let’s look at some sample C++ coding interview questions:

1. You are given a linked list “L,” Write a program function to pick a random node from the linked list.
2. Write a code to convert a given binary tree to a Doubly Linked List (DLL) in place. The left and right pointers in the nodes are to be used as previous and next pointers, respectively, in the converted DLL.
3. Write a code to count the leaves in a given binary search tree BT.
4. Write a program function to implement the serialize and deserialize functions for a given binary search tree.
5. Given an array of integers, write a program to return the next greater element for each element in the array. The array comprises all distinct numbers. If a greater element doesn’t exist to the right of a given element, the value returned in that position should be -1.
6. You are given a positive array with n positive integers. Write a program to determine the inversion count of the array.
7. You are given a binary tree T. Write a program to print the right view of the tree.
8. You’re given a binary tree T. Write a code to print the height of the binary tree.
9. For a given binary tree, write a program to connect the nodes of the binary tree that are at the same level.
10. Two node values are given for a binary search tree with unique values. Write a program to find the lowest common ancestors of the two nodes.

If you want to check out more C++ coding interview questions (problems) along with solutions to practice for technical interviews, check out our Problems Page.

How to Prepare for C++ Interviews

If you’re looking to get started with your C++ interview preparation, this section will give you some important tips to answer C++ interview questions effectively and ace your upcoming interview. Here are some tips that will help you with your prep.

• Practice theory-based questions: Knowing answers to commonly asked C++ theory-based interview questions should be an essential part of your C++ interview preparation. These questions mostly pertain to Object-Oriented programming concepts and core concepts in C++.
  

• Practice questions around problem-solving - At technical interviews, you’re required to solve problems around core data structures and algorithms. Solving these problems requires a good command of the language and diligent practice. Using power patterns to solve problems by identifying and classifying problems based on similar solution patterns is the best way to improve your problem-solving skills.
  

• Practice Mock Interviews - Another essential tip to crack tough technical interviews at FAANG+ companies is to practice mock interviews with FAANG Hiring managers. At Interview Kickstart, you get the unique opportunity to practice mocks with hiring managers who’re closely acquainted with the interview process at FAANG companies.
  

• Begin your prep well in advance - Starting your interview prep at least 5-6 weeks before your interview is key if you wish to cover all the crucial concepts adequately. Start early, pace your prep steadily, and remain consistent with your C++ interview preparation.
  

• Think out loud in the interview - This is another tip to help you ace your technical interview. By thinking out loud, you give recruiters a peek into your approach. If your approach is correct, you’re often given the green signal by the hiring manager and are awarded points even if you don’t arrive at the optimal solution.

FAQs on C++ Interview Questions

Q1. What is C++, and what is it used for?

C++ is a popular general-purpose programming language that allows developers to build scalable user interfaces, software programs, and applications.

Q2. In which interviews C++ interview questions are asked?

You can expect C++ interview questions in C ++developer interviews and coding interviews at FAANG+ companies.

Q3. Do you need in-depth knowledge of C++ to crack technical FAANG interviews?

Knowing your way around how C++ works is vital if you’re choosing C++ as your choice of language. At FAANG interviews, you need to be good with at least one Object-Oriented programming language to solve problem-styled questions in core data structures and algorithms.  

Q4. What are some C++ concepts on which tech interview questions are asked?

Some common concepts around which you’re asked C++ interview questions at tech interviews are methods, events in C++, lists, inheritance, polymorphism, abstraction, data binding, and commands used in C++.

Q5. Do you need to answer C++ interview questions to ace design interviews at FAANG+ companies?

Knowing the core concepts in C++ is crucial to ace design interviews at FAANG+ companies. Concepts like inheritance and polymorphism, among others, are extensively used to build scalable applications and systems.

Get Ready for Your Upcoming Technical Interview

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