CPP Syntax Fundamentals & Data Structures 2

Question 1

What is the output of the following code?
```cpp
int x = 5;
std::cout << x++ << " " << ++x;
```

Accepted Answer

5 7

Answer

x++ returns 5 (post-increment), then ++x increments to 7 and returns 7, giving '5 7'.

Question 2

Which container provides O(1) average-case lookup by key in C++ STL?

Accepted Answer

std::unordered_map

Answer

std::unordered_map uses a hash table, giving O(1) average-case lookup, unlike std::map which is O(log n).

Question 3

What does the following declaration create?
```cpp
int* const ptr = &x;
```

Accepted Answer

A constant pointer to an integer

Answer

int* const ptr declares a constant pointer (the pointer itself cannot be reassigned) to a non-const integer.

Question 4

Which C++ standard introduced the range-based for loop?

Accepted Answer

C++11

Answer

The range-based for loop (for (auto x : container)) was introduced in C++11.

Question 5

What is the size of an empty class in C++?

Accepted Answer

1 byte

Answer

C++ guarantees that every object has a unique address, so an empty class has size 1 byte.

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