Syntax Fundamentals & Data Structures Flashcards

Which of the following correctly declares a lambda that captures all local variables by reference?

Answer: [&](int x){ return x; }

[&] in the capture list tells the lambda to capture all local variables from the enclosing scope by reference.

What is the output of this code? ```cpp std::vector v = {1, 2, 3}; v.erase(v.begin() + 1); std::cout << v[1]; ```

Answer: 3

Erasing index 1 (value 2) shifts the remaining elements left, so v[1] becomes 3.

What is a std::pair most analogous to?

Answer: A struct with two fields 'first' and 'second' of the specified types

std::pair holds exactly two values accessible as .first and .second of the types specified in the template arguments.

Which of the following is NOT a valid way to initialize a variable in C++11?

Answer: int x := 5;

C++ does not use := for initialization; that syntax belongs to languages like Pascal or Go.

What happens when you access a std::map with a key that doesn't exist using operator[]?

Answer: It returns a default-constructed value and inserts the key

operator[] on std::map value-initializes and inserts a new element for missing keys, returning a reference to it.

In C++, what is 'object slicing'?

Answer: Losing derived class data when assigning a derived object to a base class by value

Object slicing occurs when a derived class object is assigned/copied to a base class variable by value, discarding the derived portion.

Which STL algorithm finds the first element in a range satisfying a predicate?

Answer: std::find_if

std::find_if takes a unary predicate and returns an iterator to the first element for which the predicate returns true.