#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <semaphore.h>
#include <unistd.h>
 
sem_t chopsticks[5];
 
void *philos(void *);
void eat(int);
 
int main() {
    int n[5], i;
    pthread_t T[5];
 
    for (i = 0; i < 5; i++) {
        sem_init(&chopsticks[i], 0, 1);
    }
 
    for (i = 0; i < 5; i++) {
        n[i] = i;
        pthread_create(&T[i], NULL, philos, (void *)&n[i]);
    }
 
    for (i = 0; i < 5; i++) {
        pthread_join(T[i], NULL);
    }
 
    return 0;
}
 
void *philos(void *n) {
    int ph = *(int *)n;
 
    printf("Philosopher %d wants to eat\n", ph);
 
    // To avoid deadlock: odd philosophers pick right first
    if (ph % 2 == 0) {
        printf("Philosopher %d tries to pick up left chopstick\n", ph);
        sem_wait(&chopsticks[ph]);
        printf("Philosopher %d picks left chopstick\n", ph);
 
        printf("Philosopher %d tries to pick up right chopstick\n", ph);
        sem_wait(&chopsticks[(ph + 1) % 5]);
        printf("Philosopher %d picks right chopstick\n", ph);
    } else {
        printf("Philosopher %d tries to pick up right chopstick\n", ph);
        sem_wait(&chopsticks[(ph + 1) % 5]);
        printf("Philosopher %d picks right chopstick\n", ph);
 
        printf("Philosopher %d tries to pick up left chopstick\n", ph);
        sem_wait(&chopsticks[ph]);
        printf("Philosopher %d picks left chopstick\n", ph);
    }
 
    eat(ph);
    sleep(2);
 
    printf("Philosopher %d finished eating\n", ph);
 
    sem_post(&chopsticks[(ph + 1) % 5]);
    printf("Philosopher %d puts down right chopstick\n", ph);
 
    sem_post(&chopsticks[ph]);
    printf("Philosopher %d puts down left chopstick\n", ph);
 
    return NULL;
}
 
void eat(int ph) {
    printf("Philosopher %d starts eating...\n", ph);
}
 

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