Daily C++ Interview

Introduction

The different typical interview processes

1. The Big Tech style interview process
2. The shorter interview process

auto and type deduction

1. Question 1: Explain auto type deduction!
2. Question 2: When can auto deduce undesired types?
3. Question 3: What are the advantages of using auto?
4. Question 4: What is the type of myCollection after the following declaration?
5. Question 5: What are trailing return types?
6. Question 6: Explain decltype!
7. Question 7: When to use decltype(auto)?
8. Question 8: Which data type do you get when you add two bools?

The keyword static and its different usages

1. Question 9: What does a static member variable in C++ mean?
2. Question 10: What does a static member function mean in C++?
3. Question 11: What is the static initialization order fiasco?
4. Question 12: How to solve the static initialization order fiasco?

Polymorphism, inheritance and virtual functions

1. Question 13: What is the difference between function overloading and function overriding?
2. Question 14: What is a virtual function?
3. Question 15: What is the override keyword and what are its advantages?
4. Question 16: Explain the concept of covariant return types and show a use-case where it comes in handy!
5. Question 17: What is virtual inheritance in C++ and when should you use it?
6. Question 18: Should we always use virtual inheritance? If yes, why? If not, why not?
7. Question 19: What’s the output of the following sample program? Is that what you’d expect? Why? Why not?
8. Question 20: Can you access the public and protected members and functions of a base class if you have private inheritance?
9. Question 21: What is private inheritance used for?
10. Question 22: Can you call a virtual function from a constructor or a destructor?
11. Question 23: What role does a virtual destructor play?
12. Question 24: Can we inherit from a standard container (such as std::vector)? If so what are the implications?
13. Question 25: What does a strong type mean and what advantages does it have?
14. Question 26: Explain short-circuit evaluation
15. Question 27: What is a destructor and how can we overload it?
16. Question 28: What is the output of the following piece of code and why?
17. Question 29: How to use the = delete specifier in C++?

Lambda functions

1. Question 30: What are immediately invoked lambda functions?
2. Question 31: What kind of captures are available for lambda expressions?

How to use the const qualifier in C++

1. Question 32: What is the output of the following piece of code and why?
2. Question 33: What are the advantages of using const local variables?
3. Question 34: Is it a good idea to have const members in a class?
4. Question 35: Does it make sense to return const objects by value?
5. Question 36: How should you return const pointers from a function?
6. Question 37: Should functions return const references?
7. Question 38: Should you take plain old data types by const reference as a function parameter?
8. Question 39: Should you pass objects by const reference as a function parameter?
9. Question 40: Does the signature of a function declaration has to match the signature of the function definition?
10. Question 41: Explain what consteval and constinit bring to C++?

Some best practices in modern C++

1. Question 42: What is aggregate initialization?
2. Question 43: What are explicit constructors and what are their advantages?
3. Question 44: What are user-defined literals?
4. Question 45: Why should we use nullptr instead of NULL or 0?
5. Question 46: What advantages does alias have over typedef?
6. Question 47: What are the advantages of scoped enums over unscoped enums?
7. Question 48: Should you explicitly delete unused/unsupported special functions or declare them as private?
8. Question 49: How to use the = delete specifier in C++?
9. Question 50: What is a trivial class in C++?

Smart pointers

1. Question 51: Explain the Resource acquisition is initialization (RAII) idiom
2. Question 52: When should we use unique pointers?
3. Question 53: What are the reasons to use shared pointers?
4. Question 54: When to use a weak pointer?
5. Question 55: What are the advantages of std::make_shared and std::make_unique compared to the new operator?
6. Question 56: Should you use smart pointers over raw pointers all the time?
7. Question 57: When and why should we initialize pointers to nullptr?

References, universal references, a bit of a mixture

1. Question 58: What does std::move move?
2. Question 59: What does std::forward forward?
3. Question 60: What is the difference between universal and rvalue references?
4. Question 61: What is reference collapsing?
5. Question 62: When constexpr functions are evaluated?
6. Question 63: When should you declare your functions as noexcept?

C++20

1. Question 64: What are concepts in C++?
2. Question 65: What are the available standard attributes in C++?
3. Question 66: What is 3-way comparison?
4. Question 67: Explain what consteval and constinit bring to C++?
5. Question 68: What are modules and what advantages do they bring?

Special function and the rules of how many?

1. Question 69: Explain the rule of three
2. Question 70: Explain the rule of five
3. Question 71: Explain the rule of zero
4. Question 72: What does std::move move?
5. Question 73: What is a destructor and how can we overload it?
6. Question 74: Should you explicitly delete unused/unsupported special functions or declare them as private?
7. Question 75: What is a trivial class in C++?
8. Question 76: What advantages does having a default constructor have?

Object oriented design, inheritance, polymorphism

1. Question 77: What are the differences between a class and a struct?
2. Question 78: What is constructor delegation?
3. Question 79: Explain the concept of covariant return types and show a use-case where it comes in handy!
4. Question 80: What is the difference between function overloading and function overriding?
5. Question 81: What is the override keyword and what are its advantages?
6. Question 82: Explain what is a friend class or a friend function
7. Question 83: What are default arguments? How are they evaluated in a C++ function?
8. Question 84: What is this pointer and can we delete it?
9. Question 85: What is virtual inheritance in C++ and when should you use it?
10. Question 86: Should we always use virtual inheritance? If yes, why? If not, why not?
11. Question 87: What does a strong type mean and what advantages does it have?
12. Question 88: What are user-defined literals?
13. Question 89: Why shouldn’t we use boolean arguments?
14. Question 90: Distinguish between shallow copy and deep copy
15. Question 91: Are class functions taken into consideration as part of the object size?
16. Question 92: What does dynamic dispatch mean?
17. Question 93: What are vtable and vpointer?
18. Question 94: Should base class destructors be virtual?
19. Question 95: What is an abstract class in C++?
20. Question 96: Is it possible to have polymorphic behaviour without the cost of virtual functions?
21. Question 97: How would you add functionality to your classes with the Curiously Recurring Template Pattern (CRTP)?
22. Question 98: What are the good reasons to use init() functions to initialize an object?

Observable behaviours

1. Question 99: What is observable behaviour of code?
2. Question 100: What are the characteristics of an ill-formed C++ program?
3. Question 101: What is unspecified behaviour?
4. Question 102: What is implementation-defined behaviour?
5. Question 103: What is undefined behaviour in C++?
6. Question 104: What are the reasons behind undefined behaviour’s existence?
7. Question 105: What approaches to take to avoid undefined behaviour?
8. Question 106: What is iterator invalidation? Give a few examples.

The Standard Template Library

1. Question 107: What is the STL?
2. Question 108: What are the advantages of algorithms over raw loops?
3. Question 109: Do algorithms validate ranges?
4. Question 110: Can you combine containers of different sizes?
5. Question 111: How is a vector’s memory layout organized?
6. Question 112: Can we inherit from a standard container (such as std::vector)? If so what are the implications?
7. Question 113: What is the type of myCollection after the following declaration?
8. Question 114: What are the advantages of const_iterators over iterators?
9. Question 115: Binary search an element with algorithms!
10. Question 116: What is an Iterator class?

Miscalleanous

1. Question 117: Can you call a virtual function from a constructor or a destructor?
2. Question 118: What are default arguments? How are they evaluated in a C++ function?
3. Question 119: Can virtual functions have default arguments?
4. Question 120: Should base class destructors be virtual?
5. Question 121: What is the function of the keyword mutable?
6. Question 122: What is the function of the keyword volatile?
7. Question 123: What is an inline function?
8. Question 124: What do we catch?
9. Question 125: What are the differences between references and pointers?
10. Question 126: Which of the following variable declarations compile and what would be the value of a?
11. Question 127: What will the line of code below print out and why?
12. Question 128: Explain the difference between pre- and post-increment/decrement operators
13. Question 129: What are the final values of a, b and c?
14. Question 130: Does this string declaration compile?
15. Question 131: What are Default Member Initializers in C++?
16. Question 132: What is the most vexing parse?
17. Question 133: Does this code compile? If yes, what does it do? If not, why not?
18. Question 134: What is std::string_view and why should we use it?
19. Question 135: How to check if a string starts or ends with a certain substring?
20. Question 136: What is RVO?
21. Question 137: How can we ensure the compiler performs RVO?
22. Question 138: What are the primary and mixed value categories in C++?
23. Question 139: Can you safely compare signed and unsigned integers?
24. Question 140: What is the return value of main and what are the available signatures?
25. Question 141: Should you prefer default arguments or overloading?
26. Question 142: How many variables should you declare on a line?
27. Question 143: Should you prefer a switch statement or chained if statements?
28. Question 144: What are include guards?
29. Question 145: Should you use angle brackets(<filename>) or double quotes(“filename”) to include?
30. Question 146: How many return statements should you have in a function?

C++ and algorithmic complexities

1. Question 147: Explain the differences between a std::map and a std::unordered_map!
2. Question 148: When to use a list over a vector?
3. Question 149: What are the algorithmic complexities of the most important algorithms?