100 Must-Know C++ Interview Questions and Answers 2025

C++ Basics and Language Features

1.
What are the main features of C++?
2.
Explain the difference between C and C++.
3.
What is object-oriented programming in C++?
4.
What are the access specifiers in C++ and what do they do?
5.
Explain the concept of namespaces in C++.
6.
What is the difference between ‘struct’ and ‘class’ in C++?
7.
What is a constructor and what are its types in C++?
8.
Explain the concept of destructors in C++.
9.
What is function overloading in C++?
10.
What is operator overloading in C++?

Memory Management and Pointers

11.
What is dynamic memory allocation in C++?
12.
Explain the difference between ‘new’ and ‘malloc()’.
13.
What is a memory and how can it be prevented?
14.
What is a dangling pointer?
15.
Explain the concept of smart pointers in C++.
16.
What is the difference between unique_ptr, shared_ptr, and weak_ptr?
17.
How does reference counting work in shared_ptr?
18.
What is the rule of three in C++?
19.
What is the rule of five in C++?
20.
Explain move semantics in C++.

Object-Oriented Programming Concepts

21.
What is inheritance in C++? Explain its types.
22.
What is polymorphism and how is it implemented in C++?
23.
Explain the concept of virtual functions in C++.
24.
What is a pure virtual function?
25.
What is an abstract class in C++?
26.
Explain the diamond problem in multiple inheritance and how to solve it.
27.
What is function hiding in C++?
28.
Explain the concept of friend functions and classes.
29.
What is the difference between composition and inheritance?
30.
What is RAII (Resource Acquisition Is Initialization) in C++?

Templates and Generic Programming

31.
What are templates in C++?
32.
Explain the difference between function templates and class templates.
33.
What is template specialization?
34.
How does template metaprogramming work in C++?
35.
What are variadic templates?
36.
Explain the concept of type traits in C++.
37.
What is SFINAE (Substitution Failure Is Not An Error)?
38.
How do you implement a type-safe container using templates?
39.
What are the advantages and disadvantages of using templates?
40.
Explain the concept of template argument deduction.

Exception Handling

41.
What is exception handling in C++?
42.
Explain the try, catch, and throw keywords.
43.
What is the purpose of the ‘noexcept’ specifier?
44.
How do you create custom exception classes?
45.
What happens if an exception is not caught?
46.
Explain the concept of exception safety.
47.
What is the difference between synchronous and asynchronous exceptions?
48.
How do you handle constructor failures using exceptions?
49.
What is the purpose of std::exception and its derived classes?
50.
How do you implement a stack unwinding mechanism?

Standard Template Library (STL)

51.
What is the Standard Template Library (STL)?
52.
Explain the difference between vector and list in STL.
53.
What are the associative containers in STL?
54.
How does an unordered_map work internally?
55.
What is the difference between set and multiset?
56.
Explain the concept of iterators in STL.
57.
What are function objects (functors) in STL?
58.
How do you use algorithms like sort, find, and binary_search in STL?
59.
What is the purpose of std::pair and std::tuple?
60.
Explain the concept of allocators in STL.

Concurrency and Multithreading

61.
What is multithreading in C++?
62.
How do you create and manage threads using std::thread?
63.
Explain the concept of mutex and its types in C++.
64.
What is a deadlock and how can it be prevented?
65.
How do you use condition variables for thread synchronization?
66.
What is the purpose of std::atomic?
67.
Explain the difference between std::async and std::thread.
68.
What is a thread pool and how would you implement one?
69.
How do you handle race conditions in C++?
70.
Explain the concept of memory ordering in C++ concurrency.

C++11 and Beyond Features

71.
What are lambda expressions in C++?
72.
Explain the ‘auto’ keyword and type inference.
73.
What is uniform initialization in C++11?
74.
How does range-based for loop work?
75.
What are delegating constructors?
76.
Explain the concept of rvalue references.
77.
What is perfect forwarding in C++?
78.
How do you use std::chrono for time-related operations?
79.
What are the improvements in smart pointers introduced in C++11?
80.
Explain the concept of constexpr.

Advanced C++ Concepts

81.
What is CRTP (Curiously Recurring Template Pattern)?
82.
Explain the concept of type erasure in C++.
83.
What are fold expressions in C++17?
84.
How do you implement a singleton pattern in C++?
85.
What is the purpose of std::optional?
86.
Explain the concept of concepts in C++20.
87.
What are coroutines in C++20?
88.
How do you use std::variant and std::visit?
89.
What is the purpose of std::any?
90.
Explain the concept of modules in C++20.

Performance and Optimization

91.
What is cache coherence and how does it affect C++ program performance?
92.
How do you optimize memory usage in C++ programs?
93.
Explain the concept of branch prediction and its impact on performance.
94.
What is loop unrolling and when is it beneficial?
95.
How do you profile C++ code for performance optimization?
96.
What is the difference between constexpr and inline functions in terms of performance?
97.
Explain the concept of false sharing and how to avoid it.
98.
How do you optimize code for modern CPU architectures (e.g., SIMD instructions)?
99.
What are some techniques for reducing compile times in large C++ projects?
100.
How do you implement and use lock-free data structures for better concurrency performance?

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100 C++ interview questions

What are the main features of C++?

Explain the difference between C and C++.

What is object-oriented programming in C++?

What are the access specifiers in C++ and what do they do?

Explain the concept of namespaces in C++.

What is the difference between ‘struct’ and ‘class’ in C++?

What is a constructor and what are its types in C++?

Explain the concept of destructors in C++.

What is function overloading in C++?

What is operator overloading in C++?

What is dynamic memory allocation in C++?

Explain the difference between ‘new’ and ‘malloc()’.

What is a memory and how can it be prevented?

What is a dangling pointer?

Explain the concept of smart pointers in C++.

What is the difference between unique_ptr, shared_ptr, and weak_ptr?

How does reference counting work in shared_ptr?

What is the rule of three in C++?

What is the rule of five in C++?

Explain move semantics in C++.

What is inheritance in C++? Explain its types.

What is polymorphism and how is it implemented in C++?

Explain the concept of virtual functions in C++.

What is a pure virtual function?

What is an abstract class in C++?

Explain the diamond problem in multiple inheritance and how to solve it.

What is function hiding in C++?

Explain the concept of friend functions and classes.

What is the difference between composition and inheritance?

What is RAII (Resource Acquisition Is Initialization) in C++?

What are templates in C++?

Explain the difference between function templates and class templates.

What is template specialization?

How does template metaprogramming work in C++?

What are variadic templates?

Explain the concept of type traits in C++.

What is SFINAE (Substitution Failure Is Not An Error)?

How do you implement a type-safe container using templates?

What are the advantages and disadvantages of using templates?

Explain the concept of template argument deduction.

What is exception handling in C++?

Explain the try, catch, and throw keywords.

What is the purpose of the ‘noexcept’ specifier?

How do you create custom exception classes?

What happens if an exception is not caught?

Explain the concept of exception safety.

What is the difference between synchronous and asynchronous exceptions?

How do you handle constructor failures using exceptions?

What is the purpose of std::exception and its derived classes?

How do you implement a stack unwinding mechanism?

What is the Standard Template Library (STL)?

Explain the difference between vector and list in STL.

What are the associative containers in STL?

How does an unordered_map work internally?

What is the difference between set and multiset?

Explain the concept of iterators in STL.

What are function objects (functors) in STL?

How do you use algorithms like sort, find, and binary_search in STL?

What is the purpose of std::pair and std::tuple?

Explain the concept of allocators in STL.

What is multithreading in C++?

How do you create and manage threads using std::thread?

Explain the concept of mutex and its types in C++.

What is a deadlock and how can it be prevented?

How do you use condition variables for thread synchronization?

What is the purpose of std::atomic?

Explain the difference between std::async and std::thread.

What is a thread pool and how would you implement one?

How do you handle race conditions in C++?

Explain the concept of memory ordering in C++ concurrency.

What are lambda expressions in C++?

Explain the ‘auto’ keyword and type inference.

What is uniform initialization in C++11?

How does range-based for loop work?

What are delegating constructors?

Explain the concept of rvalue references.

What is perfect forwarding in C++?