Top 50 C++ Interview Questions with Answers (Free PDF)

These are the 50 C++ questions that come up again and again in campus placements and fresher interviews, from "C vs C++" to move semantics and an LRU cache. Each answer starts with a short version you can say in 20 seconds, then explains why, with code and output.

What do the 50 C++ questions cover?

• OOP and classes. The four pillars, struct vs class, constructors, the copy constructor, Rule of 3/5/0, friend, static and const.
• Polymorphism. Virtual functions, how the vtable and vptr work, abstract classes, virtual destructors, object slicing and the diamond problem.
• Memory. Pointers vs references, new vs malloc, leaks and dangling pointers, smart pointers, RAII and undefined behaviour.
• STL and modern C++. Container complexities, vector internals, map vs unordered_map, iterator invalidation, lambdas, move semantics, perfect forwarding and C++11–20 features.
• Output and coding rounds. Predict-the-output questions, plus a String class, unique_ptr, a thread-safe Singleton and an LRU cache written in full.

How should you prepare with this PDF?

Read the short answer, say it out loud, then read the detailed answer and compile the example yourself. Questions marked most asked come up first in most interviews, so start there. The night before, go through the last pages: all 50 answers in one line each.

This is Part 2 of the Interview Q&A series. To learn each topic in depth first, see the C++ handwritten notes.