Iterators

Iterators are the essential link between STL containers and algorithms. An iterator is an object that behaves like a pointer, pointing to an element within a container. It allows you to traverse the container's elements sequentially. Every STL container provides a way to get iterators. The `.begin()` member function returns an iterator pointing to the first element of the container. The `.end()` member function returns an iterator pointing to a theoretical element that is *one past* the last element. This `end` iterator acts as a sentinel; when your traversal reaches `end`, you know you've processed all the elements. To access the element an iterator points to, you use the dereference operator (`*`), just like with a pointer. To move to the next element, you use the increment operator (`++`). A typical loop for traversing a container with an iterator looks like this: `for (std::vector<int>::iterator it = myVec.begin(); it != myVec.end(); ++it) { std::cout << *it; }`. Iterators provide a uniform interface for traversal across different container types. Whether you are using a `std::vector`, `std::list`, or `std::map`, the basic mechanism of using `begin()`, `end()`, `*`, and `++` remains the same. This abstraction allows algorithms to be written generically, so a single `std::sort` algorithm can work on any container that provides the required type of iterator.