Differentiate virtual and pure virtual functions
Company: TikTok
Role: Machine Learning Engineer
Category: Coding & Algorithms
Difficulty: Medium
Interview Round: Technical Screen
In C++, what is the difference between a virtual function and a pure virtual function? Provide syntax examples, describe dynamic dispatch via the vtable, and explain how overriding works. When does a class become abstract, and can a pure virtual function still have a definition? Discuss whether constructors or destructors should be virtual, implications for resource management, and guidelines on when to use each in interface design.
Quick Answer: This question evaluates a candidate's understanding of C++ object-oriented polymorphism and interface design, including distinctions between virtual and pure virtual functions, dynamic dispatch via the vtable, overriding semantics, abstract class formation, and lifecycle concerns for constructors and destructors.