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 <stdio.h>#include <stdlib.h>#include <pthread.h>#include <unistd.h>#include <string.h>//#define DEBUG 1#define NUM 3int n=0;pthread_mutex_t mylock=PTHREAD_MUTEX_INITIALIZER;//互斥量pthread_cond_t qready=PTHREAD_COND_INITIALIZER;//条件变量void * thread_func(void *arg){    int param=(int)arg;    char c='A'+param;    int ret,i=0;    for (; i < 10; i++)    {        pthread_mutex_lock(&mylock);        while (param != n)  //刚运行时，n = 0， param = 0,条件不成立，所以直接打印A        {#ifdef DEBUG            printf("thread %d waiting\n", param);#endif            ret = pthread_cond_wait(&qready, &mylock);            if (ret == 0)             {#ifdef DEBUG                printf("thread %d wait success\n", param);#endif            } else             {#ifdef DEBUG                printf("thread %d wait failed:%s\n", param, strerror(ret));#endif            }        }       // printf("%d ",param+1);        printf("%c ",c);  //打印A后        n=(n+1)%NUM;      //n变成了1，对线程2会产出影响！！！！        pthread_mutex_unlock(&mylock);//会唤醒所有的线程，因为当这个线程完后会等pthread_cond_wait()执行两次后才能退出while (param != n)        pthread_cond_broadcast(&qready);    }        return (void *)0;}#if 0//假设为线程2void * thread_func(void *arg)//传入值1{    int param=(int)arg;    char c='A'+param;    int ret,i=0;    for (; i < 10; i++)    {        pthread_mutex_lock(&mylock);        while (param != n)  //和线程1同时执行 parm = 1，n = 0，所以刚开始时条件满足        {#ifdef DEBUG            printf("thread %d waiting\n", param);#endif//执行到此时，等待线程1发送信号，当线程1的A打印完后，n的值也变成了1，条件就不成立了            ret = pthread_cond_wait(&qready, &mylock);            if (ret == 0)             {#ifdef DEBUG                printf("thread %d wait success\n", param);#endif            } else             {#ifdef DEBUG                printf("thread %d wait failed:%s\n", param, strerror(ret));#endif            }        }       // printf("%d ",param+1);        printf("%c ",c); //此时打印值B        n=(n+1)%NUM;    //对打印C的线程3产生影响！！！        pthread_mutex_unlock(&mylock);        pthread_cond_broadcast(&qready);    }        return (void *)0;}#endifint main(int argc, char** argv) {        int i=0,err;    pthread_t tid[NUM];    void *tret;    for(;i<NUM;i++)    {        err=pthread_create(&tid[i],NULL,thread_func,(void *)i);        if(err!=0)        {            printf("thread_create error:%s\n",strerror(err));            exit(-1);        }    }    for (i = 0; i < NUM; i++)    {        err = pthread_join(tid[i], &tret);        if (err != 0)        {            printf("can not join with thread %d:%s\n", i,strerror(err));            exit(-1);        }    }    printf("\n");    return 0;}

结果如下：