File Handling & Standard Template Library (STL) Flashcards

What is the effect of opening a file with std::ios::app mode?

Answer: All writes go to the end of the file regardless of seekp()

In append mode, every write operation automatically moves the put pointer to end-of-file before writing.

Which STL container adaptor uses a std::deque as its default underlying container?

Answer: Both std::stack and std::queue

Both std::stack and std::queue default to std::deque as their underlying container.

What does std::lower_bound() return when no element satisfies the condition?

Answer: The end iterator of the range

std::lower_bound returns the end iterator if all elements are less than the value.

Which method checks whether a std::fstream has reached end-of-file?

Answer: std::fstream::eof()

eof() returns true when the eofbit is set, indicating end-of-file has been reached.

What is the time complexity of std::list::splice()?

Answer: O(1)

std::list::splice() moves elements between lists in O(1) by relinking pointers.

Which STL iterator category supports both increment and decrement but NOT random access?

Answer: Bidirectional iterator

Bidirectional iterators support ++ and -- but not arbitrary +n or -n arithmetic.

What does std::transform() do?

Answer: Applies a function to a range and stores results in another range

std::transform applies a unary or binary operation to each element and writes results to an output range.