#include <stdio.h>                          /* This is q3.c */
#include <stdlib.h>
#include <pthread.h>

struct ts {
  pthread_mutex_t *lock;
  pthread_cond_t *cv1, *cv2;
  char *command;
  int id;
};
  
void *thread(void *arg)
{
  struct ts *T;
  int i;

  T = (struct ts *) arg;
  // usleep(1000);

  pthread_mutex_lock(T->lock);
  for (i = 0; T->command[i] != '\0'; i++) {
    if (T->command[i] == 'S') {
      pthread_mutex_unlock(T->lock); 
      sleep(1); 
      pthread_mutex_lock(T->lock);
    }
    if (T->command[i] == 'X') pthread_cond_wait(T->cv1, T->lock);
    if (T->command[i] == 'Y') pthread_cond_wait(T->cv2, T->lock);
    if (T->command[i] == 'A') pthread_cond_signal(T->cv1);
    if (T->command[i] == 'B') pthread_cond_signal(T->cv2);
    if (T->command[i] == 'P') { printf("%c ", T->id); fflush(stdout); }
    if (T->command[i] == 'E') { printf("\n"); exit(1); }
  }
  pthread_mutex_unlock(T->lock);
  return NULL;
}

main(int argc, char **argv)
{
  pthread_mutex_t lock;
  pthread_cond_t cv1, cv2;
  int i;
  pthread_t *tids;
  struct ts *T;
  void *dummy;

  pthread_mutex_init(&lock, NULL);
  pthread_cond_init(&cv1, NULL);
  pthread_cond_init(&cv2, NULL);

  T = (struct ts *) malloc(sizeof(struct ts)*(argc-1));
  tids = (pthread_t *) malloc(sizeof(pthread_t)*(argc-1));
  for (i = 0; i < argc-1; i++) {
    T[i].id = 'A' + i;
    T[i].lock = &lock;
    T[i].cv1 = &cv1;
    T[i].cv2 = &cv2;
    T[i].command = argv[i+1];
    pthread_create(tids+i, NULL, thread, (void *) (T+i));
  }
  for (i = 0; i < argc-1; i++) pthread_join(tids[i], &dummy);
  printf("\n");
}