#include #include #include using namespace std; class OrderCommand { public: virtual ~OrderCommand() = default; virtual void execute() = 0; virtual void undo() = 0; }; class Kitchen { public: void prepareDish(const string& dish) { cout << "Preparing: " << dish << endl; } void cancelDish(const string& dish) { cout << "Cancelling: " << dish << endl; } }; class PlaceOrderCommand : public OrderCommand { Kitchen* kitchen; string dish; public: PlaceOrderCommand(Kitchen* kitchen, const string& dish) : kitchen(kitchen), dish(dish) {} void execute() override { kitchen->prepareDish(dish); } void undo() override { kitchen->cancelDish(dish); } }; class CancelOrderCommand : public OrderCommand { Kitchen* kitchen; string dish; public: CancelOrderCommand(Kitchen* kitchen, const string& dish) : kitchen(kitchen), dish(dish) {} void execute() override { kitchen->cancelDish(dish); } void undo() override { kitchen->prepareDish(dish); } }; class Waiter { vector pending; vector history; public: void takeOrder(OrderCommand* command) { pending.push_back(command); } void submitOrders() { for (auto* cmd : pending) { cmd->execute(); history.push_back(cmd); } pending.clear(); } void undoLast() { if (!history.empty()) { history.back()->undo(); history.pop_back(); } } }; int main() { Kitchen kitchen; Waiter waiter; waiter.takeOrder(new PlaceOrderCommand(&kitchen, "Pasta")); waiter.takeOrder(new PlaceOrderCommand(&kitchen, "Salad")); waiter.submitOrders(); waiter.takeOrder(new CancelOrderCommand(&kitchen, "Salad")); waiter.submitOrders(); waiter.undoLast(); return 0; }

Exercise: Command Design Pattern

Exercise 1: Restaurant Order System

Exercise 2: File System Operations

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