C++ Construction and initialization test

1. What does std::set::lower_bound(key) return?

The last element less than key The first element greater than or equal to key The first element strictly greater than key The largest element in the container

lower_bound() returns the first element that is greater than or equal to the specified key.

2. What does std::set::upper_bound(key) return?

The first element greater than or equal to key The last element less than key The first element strictly greater than key The last element less than or equal to key

upper_bound() returns the first element that is strictly greater than the specified key.

3. Which property defines a Binary Search Tree?

All leaves must have the same depth Every left child is smaller and every right child is greater Every node has exactly two children The tree is always balanced

In a BST, all values in the left subtree are smaller and all values in the right subtree are greater.

4. Why are balanced trees preferred over naive BSTs?

They use less memory They guarantee O(log n) height They avoid dynamic allocation They require no rotations

Balanced trees maintain logarithmic height, making search, insert and erase efficient.

5. Which condition must always hold for an AVL tree?

Every node must be red or black The heights of left and right subtrees differ by at most one Every leaf is on the same level The tree height is exactly log₂(n)

AVL trees maintain a balance factor whose absolute value cannot exceed one.

6. Which condition is NOT a Red-Black Tree invariant?

The root is black Red nodes have black children All root-to-leaf paths contain the same number of black nodes The height difference between subtrees is at most one

Height difference ≤ 1 is an AVL property, not a Red-Black Tree property.

7. What operation is used to rebalance binary search trees?

Copying Hashing Rotations Sorting

Left and right rotations preserve BST ordering while changing tree shape.

8. Which of the following breaks aggregate initialization?

Adding another public field Adding a private data member Adding a typedef Adding a comment

A class with private members is no longer an aggregate.

9. Which initialization syntax performs aggregate initialization?

Node n(5); Node n = Node(5); Node n{5}; Node n();

Brace initialization is used for aggregates.

10. What is direct initialization?

T obj; T obj(value); T obj = value; T obj{};

Direct initialization uses parentheses.

11. What is copy initialization?

T obj(value); T obj{}; T obj = value; T obj;

Copy initialization uses the assignment-like syntax.

12. What famous parsing problem does this trigger? MyClass m(List(), List());

Double delete Rule of Three Most Vexing Parse Dangling reference

The compiler interprets this as a function declaration.

13. Which syntax avoids Most Vexing Parse?

MyClass m(); MyClass m{}; MyClass m{List(), List()}; MyClass m = List();

Brace initialization cannot be interpreted as a function declaration.

14. Why is an initializer list preferred over assignment in the constructor body?

It generates smaller executables Members are initialized directly It skips constructors It avoids templates

Initialization happens before entering the constructor body.

15. Which member must be initialized in the initializer list?

int double reference std::string

References cannot be default-initialized and assigned later.

16. In what order are members initialized?

Order of the initializer list Alphabetical order Order of declaration in the class Compiler-dependent

The declaration order always determines initialization order.

17. What is a delegating constructor?

A constructor calling a base constructor A constructor calling another constructor of the same class A constructor calling a destructor A constructor using virtual dispatch

C++11 introduced constructor delegation.

18. Why is a recursive tree destructor dangerous?

It leaks memory It may cause stack overflow It disables copy construction It cannot delete nullptr

Deep recursion can exhaust the stack.

19. Is delete nullptr valid?

No Only for arrays Yes Only in C++11

Deleting a null pointer is guaranteed to do nothing.

20. Why is setting members to nullptr inside a destructor usually useless?

The compiler forbids it The object's lifetime ends immediately after destruction nullptr is deprecated delete already clears memory

The object no longer exists after the destructor completes.

21. What does int x{}; perform?

Default initialization Copy initialization Value initialization Aggregate initialization

Value initialization zero-initializes built-in types.

22. What value does int x{} contain?

Garbage 0 1 nullptr

Value initialization of int results in zero.

23. What value does int x; contain?

0 Undefined value 1 nullptr

Local built-in variables are not initialized automatically.

24. What is the purpose of a copy constructor?

Destroy an object Initialize a new object from an existing one Assign to an existing object Move an object

Copy construction creates a new object.

25. Which signature is the canonical copy constructor?

A(A&) A(const A&) A(A) A& operator=(const A&)

The canonical copy constructor takes a const reference.

26. What is assignment?

Creating a new object Replacing the state of an existing object Destroying an object Calling a constructor

Assignment works on objects that already exist.

27. What should operator= normally return?

void A A& const A

Returning a reference enables assignment chaining.

28. Why do we check if (this != &other) in operator=?

For thread safety To detect self-assignment For move semantics For performance profiling

Self-assignment can corrupt the object if resources are released first.

29. When should a custom copy constructor usually be written?

Always Never When managing resources such as dynamic memory Whenever a class contains STL containers

STL containers already implement correct copy semantics.

30. What does '= delete' on a copy constructor do?

Deletes the object Prevents copying at compile time Deletes memory automatically Forces move semantics

The compiler rejects any attempt to copy the object.