g1201_1300.s1226_the_dining_philosophers.DiningPhilosophers Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g1201_1300.s1226_the_dining_philosophers;

// #Medium #Concurrency #2022_03_12_Time_10_ms_(83.56%)_Space_42.9_MB_(80.88%)

import java.util.concurrent.Semaphore;

public class DiningPhilosophers {
    private Semaphore[] forks = new Semaphore[5];
    private Semaphore eating = new Semaphore(4);

    public DiningPhilosophers() {
        for (int i = 0; i < 5; i++) {
            forks[i] = new Semaphore(1);
        }
    }

    // call the run() method of any runnable to execute its code
    public void wantsToEat(
            int philosopher,
            Runnable pickLeftFork,
            Runnable pickRightFork,
            Runnable eat,
            Runnable putLeftFork,
            Runnable putRightFork)
            throws InterruptedException {
        eating.acquire();
        forks[philosopher].acquire();
        forks[(philosopher + 1) % 5].acquire();
        pickLeftFork.run();
        pickRightFork.run();
        eat.run();
        putLeftFork.run();
        putRightFork.run();
        forks[philosopher].release();
        forks[(philosopher + 1) % 5].release();
        eating.release();
    }
}