#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <string.h>
#include <semaphore.h>

void* A(void* arg);
void* B(void* arg);
void* C(void* arg);

int A_counter = 0;
int B_counter = 0;
int C_counter = 0;

sem_t handler_A;
sem_t handler_B;
sem_t handler_C;







void* A(void *arg)
{

int lock = 1;
int start = 0;
int counter = 0;

	while(counter < 11)
		{
			if (start == 0)
			{
				sem_wait(&handler_A);
				printf("A");
				fflush(stdout);
				sleep(1);
				counter++;

				sem_post(&handler_B);
				start = 1;
			}
			else if (start == 1)
			{
				sem_wait(&handler_A);
				printf(" A");
				fflush(stdout);
				sleep(1);
				counter++;

				if (lock == 1)
				{
					lock = 0;
					sem_post(&handler_B);

				}
				else if (lock == 0)
				{
					sem_post(&handler_C);
					lock = 1;
				}
			}
		}
	pthread_exit(0);
}
void* B(void *arg)
{
	int start = 0;
	int counter = 0;
	while (counter < 6)
	{
		if (start == 0)
		{
			sem_wait(&handler_B);
			printf("B");
			fflush(stdout);
			sleep(1);
			counter++;

			sem_post(&handler_C);
			start = 1;
		}
		else if(start == 1)
		{
			sem_wait(&handler_B);
			printf("B");
			fflush(stdout);
			sleep(1);
			counter++;

			sem_post(&handler_A);
		}
	}

		pthread_exit(0);
}

void* C(void *arg)
{
	int counter = 0;
	while (counter < 6)
	{
		sem_wait(&handler_C);
		printf("C");
		fflush(stdout);
		sleep(1);
		counter++;

		sem_post(&handler_A);
	}

	pthread_exit(0);
}






int main()
{
	int i[3];
	pthread_t thread_a;
	pthread_t thread_b;
	pthread_t thread_c;

	i[0] = 0;
	i[1] = 1;
	i[2] = 2;

	sem_init (&handler_A, 0, 1);
	sem_init (&handler_B, 1, 0);
	sem_init (&handler_C, 0, 0);


	pthread_create (&thread_a, NULL, (void *) &A, (void *) &i[0]);
	pthread_create (&thread_b, NULL, (void *) &B, (void *) &i[1]);
	pthread_create (&thread_c, NULL, (void *) &C, (void *) &i[2]);

	pthread_join (thread_a, NULL);
	pthread_join (thread_b, NULL);
	pthread_join (thread_c, NULL);

	sem_destroy (&handler_A);
	sem_destroy (&handler_B);
	sem_destroy (&handler_C);

	exit(0);
	return 0;
}