rbegin

rbegin is a reverse iterator access function in the C++ Standard Library. It provides a means to access the last element of a container and iterate in reverse order. The concept is the opposite of begin and is complemented by rend, which marks the end of the reverse sequence. When used, rbegin returns an iterator that moves from the last element toward the first; for empty containers, rbegin equals rend.

Types and overloads: For non-const objects, rbegin returns a reverse_iterator that wraps the container’s normal iterator. For const objects, the member function rbegin() const returns a const_reverse_iterator. The corresponding end of the reverse range is rend() (and rend() const). In addition to member functions, the standard library provides non-member overloads std::rbegin and std::rend (from <iterator>) that work with containers and arrays and return reverse_iterator or const_reverse_iterator as appropriate. There are also std::crbegin and std::crend for const reverse iteration.

Usage: rbegin is commonly used in explicit reverse loops. Example:

std::vector<int> v{1, 2, 3};

for (auto it = v.rbegin(); it != v.rend(); ++it) {

// use *it

}

You can also use the non-member forms:

for (auto it = std::rbegin(v); it != std::rend(v); ++it) { ... }

rbegin and rend also apply to arrays and other standard sequence types, enabling uniform reverse traversal.

Relation to other iterators: rbegin yields a reverse_iterator that adapts a normal iterator, reversing the direction of traversal. It is part of the iteration tools alongside begin, end, and their reverse counterparts.