Board-Independent Status Indicator

#include <iostream>
using namespace std;

/*
Select exactly ONE hardware board at build time.
*/
// #define BOARD_TYPE_A
#define BOARD_TYPE_B

// --- BUILD CONFIGURATION VALIDATION ---
#if defined(BOARD_TYPE_A) && defined(BOARD_TYPE_B)
    #error "Invalid Configuration: Multiple boards selected. Select only ONE."
#endif

#if !defined(BOARD_TYPE_A) && !defined(BOARD_TYPE_B)
    #error "Invalid Configuration: No board selected. Define BOARD_TYPE_A or BOARD_TYPE_B."
#endif

// Abstract interface used by application code
class StatusIndicator {
public:
    virtual void toggle() = 0;
    virtual bool isOn() const = 0;
    virtual ~StatusIndicator() = default;
};

// --- BOARD SPECIFIC IMPLEMENTATIONS ---

#ifdef BOARD_TYPE_A
class BoardAIndicator : public StatusIndicator {
private:
    bool state = false; // Initial state OFF
public:
    void toggle() override { state = !state; }
    bool isOn() const override { return state; }
};
#endif

#ifdef BOARD_TYPE_B
class BoardBIndicator : public StatusIndicator {
private:
    bool state = false; // Initial state OFF
public:
    void toggle() override { state = !state; }
    bool isOn() const override { return state; }
};
#endif

// --- FACTORY IMPLEMENTATION ---

StatusIndicator& getStatusIndicator() {
    #ifdef BOARD_TYPE_A
        static BoardAIndicator instance;
        return instance;
    #else // BOARD_TYPE_B
        static BoardBIndicator instance;
        return instance;
    #endif
}

// DO NOT modify main()
int main() {
    int n;
    if (!(cin >> n)) return 0;

    StatusIndicator& indicator = getStatusIndicator();

    for (int i = 0; i < n; ++i) {
        int evt;
        cin >> evt;

        if (evt == 1) {
            indicator.toggle();
        }

        cout << (indicator.isOn() ? "STATUS=ON\n" : "STATUS=OFF\n");
    }

    return 0;
}