LeetCode 多线程练习2（1116. 打印零与奇偶数 / H2O 生成）

Posted 2021-09-20 Zephyr丶J

多线程练习2

1116. 打印零与奇偶数

题目描述

假设有这么一个类：

class ZeroEvenOdd {
  public ZeroEvenOdd(int n) { ... }      // 构造函数
  public void zero(printNumber) { ... }  // 仅打印出 0
  public void even(printNumber) { ... }  // 仅打印出 偶数
  public void odd(printNumber) { ... }   // 仅打印出 奇数
}

相同的一个 ZeroEvenOdd 类实例将会传递给三个不同的线程：

1. 线程 A 将调用 zero()，它只输出 0 。
2. 线程 B 将调用 even()，它只输出偶数。
3. 线程 C 将调用 odd()，它只输出奇数。

每个线程都有一个 printNumber 方法来输出一个整数。请修改给出的代码以输出整数序列 010203040506… ，其中序列的长度必须为 2n。

示例 1：

输入：n = 2
输出：“0102”
说明：三条线程异步执行，其中一个调用 zero()，另一个线程调用 even()，最后一个线程调用odd()。正确的输出为 “0102”。

示例 2：

输入：n = 5
输出：“0102030405”

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/print-zero-even-odd
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

思路

信号量

信号量简单好用，真香
超过85

class ZeroEvenOdd {
    private int n;
    
    private Semaphore ling = new Semaphore(1);
    private Semaphore ji = new Semaphore(0);
    private Semaphore ou = new Semaphore(0);

    public ZeroEvenOdd(int n) {
        this.n = n;
    }

    // printNumber.accept(x) outputs "x", where x is an integer.
    public void zero(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n; i++){
            ling.acquire();
            printNumber.accept(0);
            if(i % 2 == 1)
                ji.release();
            else
                ou.release();
        }
    }

    public void even(IntConsumer printNumber) throws InterruptedException {
        for(int i = 2; i <= n; i += 2){
            ou.acquire();
            printNumber.accept(i);
            ling.release();
        }
    }

    public void odd(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n; i += 2){
            ji.acquire();
            printNumber.accept(i);
            ling.release();
        }
    }
}

volatile+ Thread.yield()

85

class ZeroEvenOdd {
    private int n;
    
    private volatile boolean ling = true;
    private volatile boolean ou = false;
    private volatile boolean ji = false;

    public ZeroEvenOdd(int n) {
        this.n = n;
    }

    // printNumber.accept(x) outputs "x", where x is an integer.
    public void zero(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n;){
            if(!ling)
                Thread.yield();
            else{
                printNumber.accept(0);
                ling = false;
                if(i % 2 == 1)
                    ji = true;
                else    
                    ou = true;
                i++;
            }
        }    
    }

    public void even(IntConsumer printNumber) throws InterruptedException {
        for(int i = 2; i <= n;){
            if(!ou)
                Thread.yield();
            else{
                printNumber.accept(i);
                ou = false;
                ling = true;
                i += 2;
            }
        }
    }

    public void odd(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n;){
            if(!ji)
                Thread.yield();
            else{
                printNumber.accept(i);
                ji = false;
                ling = true;
                i += 2;
            }
        }
    }
}

原子类控制 + Thread.yield()

class ZeroEvenOdd {
    private int n;
    
    private AtomicInteger ji = new AtomicInteger(0);
    private AtomicInteger ou = new AtomicInteger(0);

    public ZeroEvenOdd(int n) {
        this.n = n;
    }

    // printNumber.accept(x) outputs "x", where x is an integer.
    public void zero(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n; i++){
            while(ji.get() != 0 || ou.get() != 0)
                Thread.yield();
            printNumber.accept(0);
            if(i % 2 == 1)
                ji.incrementAndGet();
            else
                ou.incrementAndGet();
        }    
    }

    public void even(IntConsumer printNumber) throws InterruptedException {
        for(int i = 2; i <= n; i += 2){
            while(ou.get() != 1)
                Thread.yield();
            printNumber.accept(i);
            ou.set(0);
        }
    }

    public void odd(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n; i += 2){
            while(ji.get() != 1)
                Thread.yield();
            printNumber.accept(i);
            ji.set(0);
        }
    }
}

ReentrantLock + Condition

85

class ZeroEvenOdd {
    private int n;

    private volatile int num = 0;
    private Lock lock = new ReentrantLock();
    private Condition ling = lock.newCondition();
    private Condition ou = lock.newCondition();
    private Condition ji = lock.newCondition();


    public ZeroEvenOdd(int n) {
        this.n = n;
    }

    // printNumber.accept(x) outputs "x", where x is an integer.
    public void zero(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n; i++){
            lock.lock();
            try{
                while(num != 0){
                    ling.await();
                }
                printNumber.accept(0);
                if(i % 2 == 1){
                    ji.signal();
                    num = 1;
                }
                else{
                    ou.signal();
                    num = 2;
                }
            } catch(Exception e){
                e.printStackTrace();
            } finally{
                lock.unlock();
            }
        }
    }

    public void even(IntConsumer printNumber) throws InterruptedException {
        for(int i = 2; i <= n; i += 2){
            lock.lock();
            try{
                while(num != 2){
                    ou.await();
                }
                printNumber.accept(i);
                ling.signal();
                num = 0;
            }catch(Exception e){
                e.printStackTrace();
            }finally{
                lock.unlock();
            }
        }
    }

    public void odd(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n; i += 2){
            lock.lock();
            try{
                while(num != 1){
                    ji.await();
                }
                printNumber.accept(i);
                ling.signal();
                num = 0;
            }catch(Exception e){
                e.printStackTrace();
            }finally{
                lock.unlock();
            }
        }
    }
}

CountDownLatch

100

class ZeroEvenOdd {
    private int n;
    
    CountDownLatch ling = new CountDownLatch(0);
    CountDownLatch ji = new CountDownLatch(1);
    CountDownLatch ou = new CountDownLatch(1);

    public ZeroEvenOdd(int n) {
        this.n = n;
    }

    // printNumber.accept(x) outputs "x", where x is an integer.
    public void zero(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n; i++){
            //变为0执行
            ling.await();
            printNumber.accept(0);
            ling = new CountDownLatch(1);
            if(i % 2 == 1)
                ji.countDown();
            else
                ou.countDown();
        }
    }

    public void even(IntConsumer printNumber) throws InterruptedException {
        for(int i = 2; i <= n; i += 2){
            ou.await();
            printNumber.accept(i);
            ou = new CountDownLatch(1);
            ling.countDown();
        }
    }

    public void odd(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n; i += 2){
            ji.await();
            printNumber.accept(i);
            ji = new CountDownLatch(1);
            ling.countDown();
        }
    }
}

SynchronousQueue

52

class ZeroEvenOdd {
    private int n;
    
    BlockingQueue<Integer> synzero = new SynchronousQueue<>();
    BlockingQueue<Integer> synodd = new SynchronousQueue<>();
    BlockingQueue<Integer> syneven = new SynchronousQueue<>();

    public ZeroEvenOdd(int n) {
        this.n = n;
    }

    // printNumber.accept(x) outputs "x", where x is an integer.
    public void zero(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n; i++){
            printNumber.accept(0);
            if(i % 2 == 1){
                //给奇数队列放东西
                synodd.put(1);
            }else
                syneven.put(1);
            //从0队列取东西，如果没有，阻塞
            synzero.take();
        }
    }

    public void even(IntConsumer printNumber) throws InterruptedException {
        for(int i = 2; i <= n; i += 2){
            syneven.take();
            printNumber.accept(i);
            synzero.put(1);
        }
    }

    public void odd(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n; i += 2){
            synodd.take();
            printNumber.accept(i);
            synzero.put(1);
        }
    }
}

BlockingQueue

100

class ZeroEvenOdd {
    private int n;
    
    private BlockingQueue<Integer> ling = new LinkedBlockingQueue<>();
    private BlockingQueue<Integer> ji = new LinkedBlockingQueue<>();
    private BlockingQueue<Integer> ou = new LinkedBlockingQueue<>();

    public ZeroEvenOdd(int n) {
        this.n = n;
    }

    // printNumber.accept(x) outputs "x", where x is an integer.
    public void zero(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n; i++){
            printNumber.accept(0);
            if(i % 2 == 1)
                ji.put(1);
            else
                ouLeetCode 多线程 1116. 打印零与奇偶数

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