#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
    for (int i = 0; i < NUM_PHILOSOPHERS; i++) {
        sem_destroy(&chopsticks[i]);
    }
 
    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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