#include <forward_list>
#define CATCH_CONFIG_MAIN
#include <catch2/catch.hpp>

std::forward_list<int>::iterator advance_forward(std::forward_list<int>::iterator it, int steps);

TEST_CASE("Advance by 0 steps returns original iterator", "[advance_forward]") {
    std::forward_list<int> flist = {10, 20, 30, 40, 50};
    auto it = flist.begin();
    auto result = advance_forward(it, 0);
    REQUIRE(result == it);
}

TEST_CASE("Advance by 2 steps returns iterator to 30", "[advance_forward]") {
    std::forward_list<int> flist = {10, 20, 30, 40, 50};
    auto it = flist.begin();
    auto result = advance_forward(it, 2);
    REQUIRE(result != flist.end());
    REQUIRE(*result == 30);
}

TEST_CASE("Advance by 5 steps returns end iterator", "[advance_forward]") {
    std::forward_list<int> flist = {10, 20, 30, 40, 50};
    auto it = flist.begin();
    auto result = advance_forward(it, 5);
    REQUIRE(result == flist.end());
}

TEST_CASE("Advance from end returns end", "[advance_forward]") {
    std::forward_list<int> flist = {10, 20, 30};
    auto end_it = flist.end();
    auto result = advance_forward(end_it, 3);
    REQUIRE(result == flist.end());
}

TEST_CASE("Advance by 1 step returns iterator to 20", "[advance_forward]") {
    std::forward_list<int> flist = {10, 20, 30, 40, 50};
    auto it = flist.begin();
    auto result = advance_forward(it, 1);
    REQUIRE(result != flist.end());
    REQUIRE(*result == 20);
}

test.cpp

This course explains how iterators work in the C++ Standard Template Library and how they connect containers and algorithms. You will learn what iterators are, how different iterator categories behave, and how to use them safely and idiomatically with STL containers and algorithms. By the end of the course, you will confidently read, write, and reason about iterator-based code, including const iterators, reverse iterators, and iterator invalidation rules.

Learn the foundational concepts of iterators, their purpose in the STL, and how to use them for basic container traversal.

Delve into the different categories of iterators, their capabilities, and which containers support each category.

Investigate how iterators behave with different STL containers, including sequence and associative containers, and the importance of const iterators.

Learn how STL algorithms interact with iterators, how to use them safely, and how to avoid iterator invalidation.

Challenge: Forward Iterator Traversal

Lösning