std::list with iterator pointing to the middle of the list

main.cpp

#include <iostream>
#include <list>

// std::list with iterator pointing to the middle of the list
int main() {
	std::list<int> lst{};
	size_t N;
	char op;
	int i;

	std::cin >> N;
	std::list<int>::iterator mid = lst.begin();

	while (N--)
	{
		std::cin >> op;
		switch (op)
		{
		case '+':
			std::cin >> i;
			lst.push_back(i);
			if (lst.size() == 1)
			{
				mid = lst.end();
			}
			else if (lst.size() == 2)
			{
				--mid;
			}
			else if (lst.size() % 2 == 1 and mid != lst.end())
			{
				++mid;
			}
			break;
		case '*':
			std::cin >> i;
			lst.insert(mid, i);
			if (lst.size() == 1)
			{
				mid = lst.end();
			}
			else if (lst.size() == 2)
			{
				--mid;
			}
			else if (lst.size() % 2 == 0 and mid != lst.end())
			{
				--mid;
			}
			break;
		case '-':
			std::cout << lst.front() << '\n';
			lst.pop_front();
			if (lst.size() % 2 == 1)
			{
				++mid;
			}
			break;
		}
	}

	return EXIT_SUCCESS;
}