并发 练习代码

#include 
     
      #include 
      
       #include 
       
        #include 
        
         using namespace std;std::mutex mtx;std::condition_variable cv;char arr[] = { 'a','b','c' };char message = 'a';void test(int i) {    for(int j = 0 ;j < 10;++j){        std::unique_lock
         
           lk(mtx);        cv.wait(lk, [=] {
   return message == arr[i]; });        std::cout << arr[i];        message = arr[(i + 1) % 3];        lk.unlock();        cv.notify_all();    }}int main(){    std::thread t[3];    for (int i = 0; i < 3; ++i) {        t[i] = std::thread(test,i);    }    for (int i = 0; i < 3; ++i) {        t[i].join();    }    std::cout << std::endl;    return 0;}