덱

#include <iostream> #include <deque> #define endl "\n" int N; std::deque<int> dq; void io_faster() { std::ios_base::sync_with_stdio(false); std::cin.tie(0); std::cout.tie(0); } void input() { io_faster(); std::cin >> N; } void solve() { int num; std::string op; while (N--) { std::cin >> op; if (op == "push_back") { std::cin >> num; dq.push_back(num); } else if (op == "push_front") { std::cin >> num; dq.push_front(num); } else if (op == "front") { if (dq.size()) std::cout << dq.front() << endl; else std::cout << -1 << endl; } else if (op == "size") { std::cout << dq.size() << endl; } else if (op == "back") { if (dq.size()) std::cout << dq.back() << endl; else std::cout << -1 << endl; } else if (op == "empty") { if (dq.size()) std::cout << 0 << endl; else std::cout << 1 << endl; } else if (op == "pop_front") { if (dq.size()) { std::cout << dq.front() << endl; dq.pop_front(); } else std::cout << -1 << endl; } else if (op == "pop_back") { if (dq.size()) { std::cout << dq.back() << endl; dq.pop_back(); } else std::cout << -1 << endl; } } } int main() { input(); solve(); return (0); }