C++ interviews are deep because the language is. They test object-oriented design, the Standard Template Library, memory and ownership, and the modern features (smart pointers, move semantics) that separate current C++ from legacy C++. Used heavily in systems, finance, gaming, and embedded roles. Here are the C++ interview questions that actually get asked, with answers.
OOP in C++
- The four OOP pillars in C++ (our OOPs guide).
- What is a virtual function, and how does the vtable work?
- Virtual vs pure virtual function; abstract classes.
- What is a virtual destructor and why does it matter?
- Function overloading vs overriding; operator overloading.
Pointers, references & memory
- Pointer vs reference — key differences.
- Smart pointers — unique_ptr, shared_ptr, weak_ptr.
- What is RAII?
- Shallow vs deep copy; the rule of three/five.
- Move semantics and rvalue references.
The STL
- vector vs list vs deque — when to use each.
- map vs unordered_map; set vs unordered_set.
- Iterators and iterator invalidation.
- What are templates, and template specialization?
How to prepare
C++ rounds probe the "why" behind features. Practise explaining ownership, virtual dispatch, and container choices out loud. Greenroom runs spoken technical interviews that follow up on your reasoning. Pair it with our C and OOPs guides.
Frequently asked questions
What are the most common C++ interview questions?
Common C++ questions cover OOP (the four pillars, virtual functions and the vtable, pure virtual functions, virtual destructors, overloading vs overriding), memory and ownership (pointer vs reference, smart pointers, RAII, the rule of three/five, move semantics), and the STL (vector vs list, map vs unordered_map, iterators and iterator invalidation, templates).
What is a virtual function in C++?
A virtual function is a member function declared with the virtual keyword that can be overridden in derived classes, enabling runtime polymorphism. When called through a base-class pointer or reference, the actual derived implementation runs, resolved via a per-class table of function pointers called the vtable. A virtual destructor is essential when deleting derived objects through base pointers.
What are smart pointers in C++?
Smart pointers are RAII wrappers that manage dynamic memory automatically. unique_ptr provides exclusive ownership and frees the resource when it goes out of scope; shared_ptr provides shared ownership via reference counting; and weak_ptr is a non-owning reference that breaks reference cycles. They prevent leaks and dangling pointers compared to raw new/delete.
How should I prepare for a C++ interview?
Go deep on virtual functions and the vtable, smart pointers and ownership, RAII and move semantics, and STL container trade-offs, since C++ interviews probe the 'why' behind features. Practise explaining these out loud, ideally with a voice-based mock interview that follows up, because surface-level knowledge cracks quickly under follow-up questions.