#include <stdio.h>
#include <semaphore.h>
#include <pthread.h>
#include <unistd.h>
#include <stdlib.h>
 
#define NUM_PHILOSOPHERS 3
 
sem_t chopsticks[NUM_PHILOSOPHERS];
 
void *philosopher(void *arg);
 
int main() {
    pthread_t t[NUM_PHILOSOPHERS];
 
    // Initialize semaphores (chopsticks)
    for (int i = 0; i < NUM_PHILOSOPHERS; i++) {
        sem_init(&chopsticks[i], 0, 1); // Initialize each chopstick to 1 (unlocked)
    }
 
    // Create philosopher threads
    for (int i = 0; i < NUM_PHILOSOPHERS; i++) {
        int *p = (int *)malloc(sizeof(int));
        *p = i;
        pthread_create(&t[i], NULL, philosopher, (void *)p);
    }
 
    // Join philosopher threads
    for (int i = 0; i < NUM_PHILOSOPHERS; i++) {
        pthread_join(t[i], NULL);
    }
 
    // Destroy semaphores
 
 
    return 0;
}
 
void *philosopher(void *arg) {
    int id = *(int *)arg;
    free(arg); // Free allocated memory for philosopher ID
 
    printf("Philosopher %d is thinking\n", id);
    sleep(1);
 
    printf("Philosopher %d wants to eat\n", id);
 
    sem_wait(&chopsticks[id]);                  // Pick up left chopstick
    sem_wait(&chopsticks[(id + 1) % NUM_PHILOSOPHERS]); // Pick up right chopstick
 
    printf("Philosopher %d is eating\n", id);
    sleep(2); // Simulate eating
 
    sem_post(&chopsticks[(id + 1) % NUM_PHILOSOPHERS]); // Release right chopstick
    sem_post(&chopsticks[id]);                  // Release left chopstick
 
    printf("Philosopher %d stops eating and came back to thinking state\n", id);
 
    return NULL;
}
 

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