Runtime Driver Selection

#include <iostream>
using namespace std;

class Driver {
public:
    virtual void start() {
        cout << "Generic driver started" << endl;
    }
};

class SpiDriver : public Driver {
public:
    void start() {
        cout << "SPI driver started" << endl;
    }
};

class I2cDriver : public Driver {
public:
    void start() {
        cout << "I2C driver started" << endl;
    }
};

int main() {
    int mode;
    cin >> mode;

    SpiDriver spi;
    I2cDriver i2c;

    Driver* driver = nullptr;

    if (mode == 0) {
        driver = &spi;
    } else {
        driver = &i2c;
    }

    driver->start();   // correct behavior

    return 0;
}

Solving Approach