第四题（迅雷笔试题）：编写一个程序，开启3个线程，这3个线程的ID分别为A、B、C，每个线程将自己的ID在屏幕上打印10遍，要求输出结果必须按ABC的顺序显示；如：ABCABC….依次递推。

 #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=;
 void *ThreadFunc(void *arg)
 {
     int num=(int )arg;
     for (int i = ; i < ; ++i)
     {
         pthread_mutex_lock(&myloack);
         while (n!=num)
             pthread_cond_wait(&mycond,&myloack);

         if (num==)
             cout<<"A";
         else if(num==)
             cout<<"B";
         else
             cout<<"C"<<endl;
         n=(n+)%;
         pthread_mutex_unlock(&myloack);
         pthread_cond_broadcast(&mycond);
     }
     return (void *);
 }
 int  main(int argc, char const *argv[])
 {
     pthread_t id[];
     for (int i = ; i < ; ++i)
     {
         int err=pthread_create(&id[i],NULL,ThreadFunc,(void *)i);
         if (err!=)
         {
             cout<<"create err:"<<endl;
             exit(-);
         }

     }

     for (int i = ; i < ; ++i)
     {
         int ret=pthread_join(id[i],NULL);
         if (ret!=)
         {
             cout<<"join err:"<<endl;
             exit(-);
         }
     }
     return ;
 }