交替输出ABAB

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include <string.h>
//#define DEBUG 1
#define NUM 2

int 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)
        {

            ret = pthread_cond_wait(&qready, &mylock);

        }
       // printf("%d ",param+1);
        printf("%c ",c);
        n=(n+1)%NUM;
        pthread_mutex_unlock(&mylock);
        pthread_cond_broadcast(&qready);
    }    
    return (void *)0;
}
int 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);
  
    }
	
    for (i = 0; i < NUM; i++)
    {
        err = pthread_join(tid[i], NULL);
   
    }
    printf("\n");
    return 0;
}