[C++知识库]交替打印ABC多线程（互斥量+条件变量）

#include <iostream>
#include <thread>
#include <mutex>
#include <condition_variable>
using namespace std;

mutex mymutex; //全局锁
condition_variable cv;//全局条件变量
int flag = 0;

void func_a() {
	unique_lock<mutex> locka(mymutex);
	for (int i = 0; i < 5; i++) {
		while (flag != 0) cv.wait(locka);
		//如果falg == 0，不会阻塞，直接运行后面的
		cout << "thread1: A" << endl;
		flag = 1;
		cv.notify_all();
	}
	cout << "thread1 finsh" << endl;
}

void func_b() {
	unique_lock<mutex> lockb(mymutex);
	for (int i = 0; i < 5; i++) {
		while (flag != 1) cv.wait(lockb);
		//如果falg == 1，不会阻塞，直接运行后面的
		cout << "thread2: B" << endl;
		flag = 2;
		cv.notify_all();
	}
	cout << "thread2 finsh" << endl;
}

void func_c() {
	unique_lock<mutex> lockc(mymutex);
	for (int i = 0; i < 5; i++) {
		while (flag != 2) cv.wait(lockc);
		//如果falg == 2，不会阻塞，直接运行后面的
		cout << "thread3: C" << endl;
		flag = 0;
		cv.notify_all();
	}
	cout << "thread2 finsh" << endl;
}

int main() {
	thread th1(func_a);
	thread th2(func_b);
	thread th3(func_c);

	th1.join();
	th2.join();
	th3.join();

	return 0;
}