#include <cstdio>
#include <ctime>

#include <unistd.h>

class StopWatch
{
public:
    StopWatch();

    void start();
    void stop();
    void reset();
    double get_elapsed_time();
    bool is_running();

private:
    double elapsed_time;
    bool running;
    time_t start_time;
};

StopWatch::StopWatch()
{
    running = false;
    elapsed_time = 0;
}

void
StopWatch::reset()
{
    running = false;
    elapsed_time = 0;
}

bool
StopWatch::is_running()
{
    return running;
}

void
StopWatch::start()
{
    if (running) {
        return;
    }

    start_time = time(NULL);
    running = true;
}

void
StopWatch::stop()
{
    if (! running) {
        return;
    }

    time_t current_time = time(NULL);
    running = false;
    elapsed_time += difftime(current_time, start_time);
}

double
StopWatch::get_elapsed_time()
{
    double elapsed = elapsed_time;

    if (running) {
        time_t current_time = time(NULL);
        elapsed += difftime(current_time, start_time);
    }

    return elapsed;
}

int
main()
{
    StopWatch watch;

    watch.start();
    for (int i = 0; i < 5; ++i) {
        sleep(1);
        printf("Elapsed time: %f\n", watch.get_elapsed_time());
    }
    watch.stop();
    sleep(5);
    printf("Elapsed time: %f\n", watch.get_elapsed_time());

    return 0;
}