多线程 Leetcode 打印零与奇偶数

现有函数 printNumber 可以用一个整数参数调用，并输出该整数到控制台。

• 例如，调用 printNumber(7) 将会输出 7 到控制台。

给你类 ZeroEvenOdd 的一个实例，该类中有三个函数：zero、even 和 odd 。ZeroEvenOdd 的相同实例将会传递给三个不同线程：

• 线程 A：调用 zero() ，只输出 0
• 线程 B：调用 even() ，只输出偶数
• 线程 C：调用 odd() ，只输出奇数

修改给出的类，以输出序列 "010203040506..." ，其中序列的长度必须为 2n 。

实现 ZeroEvenOdd 类：

• ZeroEvenOdd(int n) 用数字 n 初始化对象，表示需要输出的数。
• void zero(printNumber) 调用 printNumber 以输出一个 0 。
• void even(printNumber) 调用printNumber 以输出偶数。
• void odd(printNumber) 调用 printNumber 以输出奇数。

示例 1：

输入：n = 2
输出："0102"
解释：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"

1. Semaphore

class ZeroEvenOdd {private int n;private Semaphore zeroSema = new Semaphore(1);private Semaphore oddSema = new Semaphore(0);//奇数private Semaphore evenSema = new Semaphore(0);//偶数public ZeroEvenOdd(int n) {this.n = n;}public void zero(IntConsumer printNumber) throws InterruptedException {for (int i = 1; i <= n; i++) {zeroSema.acquire();printNumber.accept(0);if (i % 2!= 0) {//奇数oddSema.release();} else {evenSema.release();}}}public void even(IntConsumer printNumber) throws InterruptedException {for (int i = 1; i <= n; i++) {if (i % 2== 0) {//偶数 打印偶数 并释放zero的线程evenSema.acquire();printNumber.accept(i);zeroSema.release();}}}public void odd(IntConsumer printNumber) throws InterruptedException {for (int i = 1; i <= n; i++) {if (i % 2 != 0) {//奇数，打印奇数，并释放zero的线程oddSema.acquire();printNumber.accept(i);zeroSema.release();}}}
}

2. synchronized

class ZeroEvenOdd {private int n;private final Object ob=new Object();private volatile int flag=0;public ZeroEvenOdd(int n) {this.n = n;}public void zero(IntConsumer printNumber) throws InterruptedException {for (int i = 1; i <= n; i++) {synchronized (ob){while (flag!=0){ob.wait();}printNumber.accept(0);if(i%2==0)flag=2;elseflag=1;ob.notifyAll();}}}public void even(IntConsumer printNumber) throws InterruptedException {for (int i = 1; i <= n; i++) {if (i % 2== 0) {//偶数 打印偶数 并释放zero的线程synchronized (ob){while (flag!=2){ob.wait();}printNumber.accept(i);flag=0;ob.notifyAll();}}}}public void odd(IntConsumer printNumber) throws InterruptedException {for (int i = 1; i <= n; i++) {if (i % 2!= 0) {//偶数 打印偶数 并释放zero的线程synchronized (ob){while (flag!=1){ob.wait();}printNumber.accept(i);flag=0;ob.notifyAll();}}}}
}

3. CountDownLatch

class ZeroEvenOdd {private int n;private CountDownLatch countDownLatch_zero=new CountDownLatch(0);private CountDownLatch countDownLatch_even=new CountDownLatch(1);private CountDownLatch countDownLatch_odd=new CountDownLatch(1);public ZeroEvenOdd(int n) {this.n = n;}public void zero(IntConsumer printNumber) throws InterruptedException {for (int i = 1; i <= n; i++) {countDownLatch_zero.await();printNumber.accept(0);countDownLatch_zero=new CountDownLatch(1);if (i % 2!= 0) {//奇数countDownLatch_odd.countDown();} else {countDownLatch_even.countDown();}}}public void even(IntConsumer printNumber) throws InterruptedException {for (int i = 1; i <= n; i++) {if (i % 2== 0) {//偶数 打印偶数 并释放zero的线程countDownLatch_even.await();printNumber.accept(i);countDownLatch_even=new CountDownLatch(1);countDownLatch_zero.countDown();}}}public void odd(IntConsumer printNumber) throws InterruptedException {for (int i = 1; i <= n; i++) {if (i % 2 != 0) {//奇数，打印奇数，并释放zero的线程countDownLatch_odd.await();printNumber.accept(i);countDownLatch_odd=new CountDownLatch(1);countDownLatch_zero.countDown();}}}
}

4. Lock

class ZeroEvenOdd {private int n;private volatile int flag=0;Lock lock=new ReentrantLock();Condition condition_zero = lock.newCondition();Condition conditon_even = lock.newCondition();Condition condition_odd = lock.newCondition();public ZeroEvenOdd(int n) {this.n = n;}public void zero(IntConsumer printNumber) throws InterruptedException {for (int i = 1; i <= n; i++) {lock.lock();try{while (flag!=0){condition_zero.await();}printNumber.accept(0);if(i%2==0) {flag = 2;conditon_even.signal();}else {flag = 1;condition_odd.signal();}}finally {lock.unlock();}}}public void even(IntConsumer printNumber) throws InterruptedException {for (int i = 1; i <= n; i++) {if (i % 2== 0) {//偶数 打印偶数 并释放zero的线程lock.lock();try {while (flag != 2) {conditon_even.await();}printNumber.accept(i);flag = 0;condition_zero.signal();}finally {lock.unlock();}}}}public void odd(IntConsumer printNumber) throws InterruptedException {for (int i = 1; i <= n; i++) {if (i % 2!= 0) {//偶数 打印偶数 并释放zero的线程lock.lock();try {while (flag != 1) {condition_odd.await();}printNumber.accept(i);flag = 0;condition_zero.signal();}finally {lock.unlock();}}}}
}