（某培训机构的练习题）子线程循环 10 次，接着主线程循环 100 次，接着又回到子线程循环 10 次，接着再回到主线程又循环 100 次，如此循环50次，试写出代码。

从题目看，首先想到是使用条件变量来实现，以下是实现代码：

#include <iostream>
#include <stdlib.h>
#include <pthread.h>
using namespace std;

pthread_mutex_t myloack=PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t mycond=PTHREAD_COND_INITIALIZER;
int n=0;
void *TreadFuncMa(void *arg)
{
    for (int i = 0; i < 50; ++i)
    {
        pthread_mutex_lock(&myloack);

        if(n!=0)
            pthread_cond_wait(&mycond,&myloack);

        for (int i = 0; i < 10; ++i)
            cout<<"A"<<" ";

        cout<<endl;
        n++;

        pthread_mutex_unlock(&myloack);
        pthread_cond_broadcast(&mycond);
    }
    return (void *)0;
}
int  main(int argc, char const *argv[])
{
    pthread_t id;
    int ret=pthread_create(&id,NULL,TreadFuncMa,NULL);
    if (rt!=0)
    {
        return 0;
    }

    /* code */
    for (int i = 0; i < 50; ++i)
    {
        pthread_mutex_lock(&myloack);

        if(n!=1)
            pthread_cond_wait(&mycond,&myloack);

        for (int i = 0; i < 100; ++i)
            cout<<"B"<<" ";

        cout<<endl;
        n--;
        
        pthread_mutex_unlock(&myloack);
        pthread_cond_broadcast(&mycond);
    }
    pthread_join(id,NULL);
    return 0;
}