代码

#include<iostream>
#include<thread>
#include<mutex>
#include<condition_variable>
using namespace std;
mutex mtx;
condition_variable cv;
int flag=0;
void A(){unique_lock<mutex>lk(mtx);int count=0;while(count<10){while(flag!=0) cv.wait(lk);cout<<"thread1 : a"<<endl;count++;this_thread::sleep_for(chrono::milliseconds(500));flag=1;cv.notify_all();}cout<<"thread 1 finish"<<endl;}
void B(){unique_lock<mutex>lk(mtx);int count=0;while(count<10){while(flag!=1) cv.wait(lk);cout<<"thread 2 : b"<<endl;this_thread::sleep_for(chrono::milliseconds(500));flag=2;cv.notify_all();count++;}cout<<"thread 2 finished"<<endl;}
void C(){unique_lock<mutex>lk(mtx);int count=0;while(count<10){while(flag!=2) cv.wait(lk);cout<<"thread 3 : c"<<endl;this_thread::sleep_for(chrono::milliseconds(500));flag=0;cv.notify_all();count++;}cout<<"thread 3 finished"<<endl;}
int main(){thread t1(A);thread t2(B);thread t3(C);t1.join();t2.join();t3.join();return 0;}

结果