220-让三个线程循环打印ABC

我会带着你远行 2022-11-07 14:39 202阅读 0赞

## 互斥锁+条件变量实现版本 ##

#include <iostream>
    #include <thread>
    #include <condition_variable>
    #include <mutex>
    using namespace std;
    
    condition_variable cv;//条件变量
    mutex mx;//互斥量
    int isReady = 0;//初始化为0
    
    void printf_1()
    {
        
        unique_lock<mutex> lc(mx);
        int i = 0;
        while(i < 10)
        {
        
            while(isReady != 0)//如果还没有准备好 那么久开始等待，并且释放锁
                cv.wait(lc);
            cout << "A" ;
            isReady = 1;
            i++;
            cv.notify_all();
        }
    }
    
    void printf_2()
    {
        
        unique_lock<mutex> lc(mx);
        int i = 0;
        while(i < 10)
        {
        
            while(isReady != 1)
                cv.wait(lc);
            cout << "B" ;
            isReady = 2;
            i++;
            cv.notify_all(); //我已经打印完了 轮到别的线程打印了
        }
    }
    
    void printf_3()
    {
        
        unique_lock<mutex> lc(mx);
        int i = 0;
        while (i < 10)
        {
        
            while (isReady != 2)
                cv.wait(lc);
            cout << "C" ;
            isReady = 0;
            i++;
            cv.notify_all(); //我已经打印完了,轮到别的线程打印了
        }
    }
    
    int main()
    {
        
        thread t1(printf_1);
        thread t2(printf_2);
        thread t3(printf_3);
        t1.join();
        t2.join();
        t3.join();
    
        return 0;
    }

**运行截图如下：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0xJTlpFWVU2NjY_size_16_color_FFFFFF_t_70_pic_center]

## 信号量实现版本 ##

#include <iostream>
    #include <thread>
    #include <semaphore.h>
    using namespace std;
    
    sem_t sem1;
    sem_t sem2;
    sem_t sem3;
    
    void pthread_fun1()
    {
        
        int i = 0;
        for (; i < 10; ++i)
        {
        
            sem_wait(&sem1); //P操作
            cout << "A" ;
            std::this_thread::sleep_for(std::chrono::milliseconds(200));
            sem_post(&sem2); //V操作
        }
    }
    void pthread_fun2()
    {
        
        int i = 0;
        for (; i < 10; ++i)
        {
        
            sem_wait(&sem2);
            cout << "B" ;
            std::this_thread::sleep_for(std::chrono::milliseconds(200));
            sem_post(&sem3);
        }
    }
    void pthread_fun3()
    {
        
        int i = 0;
        for (; i < 10; ++i)
        {
        
            sem_wait(&sem3);
            cout << "C" ;
            std::this_thread::sleep_for(std::chrono::milliseconds(200));
            sem_post(&sem1);
        }
    }
    int main()
    {
        
        sem_init(&sem1, 0, 1); //初始化
        sem_init(&sem2, 0, 0);
        sem_init(&sem3, 0, 0);
        thread s1(pthread_fun1);
        thread s2(pthread_fun2);
        thread s3(pthread_fun3);
        s1.join();
        s2.join();
        s3.join();
    
        sem_destroy(&sem1); //销毁信号量
        sem_destroy(&sem2);
        sem_destroy(&sem3);
    
        return 0;
    }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0xJTlpFWVU2NjY_size_16_color_FFFFFF_t_70_pic_center]: /images/20221023/390e9cec022743838a4674974221d80e.png