1195_FizzBuzz.cpp

#include <condition_variable>
#include <functional>
#include <future>
#include <iostream>

class FizzBuzz {
private:
    int n;
    int mPos;
    std::mutex mMutex;
    std::condition_variable mConditionVariable;
    bool mFinished;

public:
    FizzBuzz(int n) {
        this->n = n;
        this->mPos = 1;
        this->mFinished = false;
    }

    // printFizz() outputs "fizz".
    void fizz(std::function<void()> printFizz) {
        std::unique_lock<std::mutex> lock(mMutex);
        mConditionVariable.wait(lock, [=]() {
            return (mPos % 3 == 0) && (mPos % 5 != 0) || mFinished;
        });
        if (mFinished) {
            lock.unlock();
            mConditionVariable.notify_all();
            return;
        }
        printFizz();
        if (mPos == n) {
            mFinished = true;
            lock.unlock();
            mConditionVariable.notify_all();
            return;
        }
        mPos += 1;
        lock.unlock();
        mConditionVariable.notify_all();
        fizz(printFizz);
    }

    // printBuzz() outputs "buzz".
    void buzz(std::function<void()> printBuzz) {
        std::unique_lock<std::mutex> lock(mMutex);
        mConditionVariable.wait(lock, [=]() {
            return (mPos % 5 == 0) && (mPos % 3 != 0) || mFinished;
        });
        if (mFinished) {
            lock.unlock();
            mConditionVariable.notify_all();
            return;
        }
        printBuzz();
        if (mPos == n) {
            mFinished = true;
            lock.unlock();
            mConditionVariable.notify_all();
            return;
        }
        mPos += 1;
        lock.unlock();
        mConditionVariable.notify_all();
        buzz(printBuzz);
    }

    // printFizzBuzz() outputs "fizzbuzz".
    void fizzbuzz(std::function<void()> printFizzBuzz) {
        std::unique_lock<std::mutex> lock(mMutex);
        mConditionVariable.wait(lock, [=]() {
            return (mPos % 3 == 0) && (mPos % 5 == 0) || mFinished;
        });
        if (mFinished) {
            lock.unlock();
            mConditionVariable.notify_all();
            return;
        }
        printFizzBuzz();
        if (mPos == n) {
            mFinished = true;
            lock.unlock();
            mConditionVariable.notify_all();
            return;
        }
        mPos += 1;
        lock.unlock();
        mConditionVariable.notify_all();
        fizzbuzz(printFizzBuzz);
    }

    // printNumber(x) outputs "x", where x is an integer.
    void number(std::function<void(int)> printNumber) {
        std::unique_lock<std::mutex> lock(mMutex);
        mConditionVariable.wait(lock, [=]() {
            return (mPos % 3 != 0) && (mPos % 5 != 0) || mFinished;
        });
        if (mFinished) {
            lock.unlock();
            mConditionVariable.notify_all();
            return;
        }
        printNumber(mPos);
        if (mPos == n) {
            mFinished = true;
            lock.unlock();
            mConditionVariable.notify_all();
            return;
        }
        mPos += 1;
        lock.unlock();
        mConditionVariable.notify_all();
        number(printNumber);
    }
};

int main(int argc, char *argv[]) {
    std::function<void()> printFizz = []() { std::cout << "Fizz"; };
    std::function<void()> printBuzz = []() { std::cout << "Buzz"; };

    std::function<void()> printFizzBuzz = []() { std::cout << "FizzBuzz"; };

    std::function<void(int)> printNumber = [](int num) { std::cout << num; };

    FizzBuzz fizzBuzz(17);
    auto fizz = std::async(&FizzBuzz::fizz, &fizzBuzz, printFizz);
    auto buzz = std::async(&FizzBuzz::buzz, &fizzBuzz, printBuzz);
    auto fizzbuzz = std::async(&FizzBuzz::fizzbuzz, &fizzBuzz, printFizzBuzz);
    auto number = std::async(&FizzBuzz::number, &fizzBuzz, printNumber);

    fizz.wait();
    buzz.wait();
    fizzbuzz.wait();
    number.wait();

    return 0;
}