[Java]LeetCode1116. 打印零与奇偶数 | Print Zero Even Odd

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Suppose you are given the following code:

class ZeroEvenOdd {
  public ZeroEvenOdd(int n) { ... }  // constructor
public void zero(printNumber) { ... } // only output 0's
public void even(printNumber) { ... } // only output even numbers
public void odd(printNumber) { ... } // only output odd numbers
}
The same instance of ZeroEvenOdd will be passed to three different threads:

Thread A will call zero() which should only output 0's.
Thread B will call even() which should only ouput even numbers.
Thread C will call odd() which should only output odd numbers.
Each of the thread is given a printNumber method to output an integer. Modify the given program to output the series 010203040506... where the length of the series must be 2n.

Example 1:

Input: n = 2
Output: "0102"
Explanation: There are three threads being fired asynchronously. One of them calls zero(), the other calls even(), and the last one calls odd(). "0102" is the correct output.
Example 2:

Input: n = 5
Output: "0102030405"

---

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：

线程 A 将调用 zero()，它只输出 0 。
线程 B 将调用 even()，它只输出偶数。
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"

---

4ms

import java.util.concurrent.*;

class ZeroEvenOdd {
    private int n;
    Semaphore s1, s2, s3;
    
    public ZeroEvenOdd(int n) {
        this.n = n;
        s1 = new Semaphore(1);
        s2 = new Semaphore(0);
        s3 = new Semaphore(0);
    }

    // printNumber.accept(x) outputs "x", where x is an integer.
    public void zero(IntConsumer printNumber) throws InterruptedException {
        for (int i = 0; i < n; i++) {
            s1.acquire();
            printNumber.accept(0);
            if (i % 2 == 0) {
                s3.release();
            } else {
                s2.release();
            }
        }
    }

    public void even(IntConsumer printNumber) throws InterruptedException {
        for (int i = 2; i <= n; i += 2) {
            s2.acquire();
            printNumber.accept(i);
            s1.release();
        }
    }

    public void odd(IntConsumer printNumber) throws InterruptedException {
        for (int i = 1; i <= n; i += 2) {
            s3.acquire();
            printNumber.accept(i);
            s1.release();
        }
    }
}

---

7ms

import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.Condition;
import java.util.function.IntConsumer;
class ZeroEvenOdd {
    private int n;
    private ReentrantLock lock = new ReentrantLock();
    private Condition z = lock.newCondition();
    private Condition e = lock.newCondition();
    private Condition o = lock.newCondition();
    private boolean isZero = true;
    private boolean isOld = true;
    public ZeroEvenOdd(int n) {
        this.n = n;
    }

    // printNumber.accept(x) outputs "x", where x is an integer.
    public void zero(IntConsumer printNumber) throws InterruptedException {
        lock.lock();
        for (int i = 1; i <= n; i++) {
            if (!isZero) {
                z.await();
            }
            printNumber.accept(0);
            isZero = false;
            if (i%2!=0) {
                o.signal();
            } else {
                e.signal();
            }
        }
        lock.unlock();
    }

    public void even(IntConsumer printNumber) throws InterruptedException {
        lock.lock();
        for (int i = 2; i <= n; i+=2) {
            if (isZero||isOld) {
                e.await();
            }
            printNumber.accept(i);
            isZero = true;
            isOld = true;
            z.signal();
        }
        lock.unlock();
    }

    public void odd(IntConsumer printNumber) throws InterruptedException {
        lock.lock();
        for (int i = 1; i <= n; i+=2) {
            if (isZero||!isOld) {
                o.await();
            }
            printNumber.accept(i);
            isZero = true;
            isOld=false;
            z.signal();
        }
        lock.unlock();
    }
}

---

8ms

import java.util.concurrent.locks.*;
class ZeroEvenOdd {
    private int n;
    private volatile boolean e = false;
    private volatile boolean o = false;
    private ReentrantLock lock = new ReentrantLock();
    private Condition zeroCondition = lock.newCondition();
    private Condition evenCondition = lock.newCondition();
    private Condition oddCondition = 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 {
                if (i != 1) {
                    zeroCondition.await();
                }
                printNumber.accept(0);
                if (isOdd(i)) {
                    o = true;
                    oddCondition.signal();
                } else {
                    e = true;
                    evenCondition.signal();
                }
            } finally {
                lock.unlock();
            }
        }
    }

    public void even(IntConsumer printNumber) throws InterruptedException {
        for (int i = 2; i <= n; i += 2) {
            lock.lock();
            try {
                while (!e) {
                    evenCondition.await();
                }
                e = false;
                printNumber.accept(i);
                zeroCondition.signal();
            } finally {
                lock.unlock();
            }
        }

    }

    public void odd(IntConsumer printNumber) throws InterruptedException {
        for (int i = 1; i <= n; i += 2) {
            lock.lock();
            try {
                while (!o) {
                    oddCondition.await();
                }
                o = false;
                printNumber.accept(i);
                zeroCondition.signal();
            } finally {
                lock.unlock();
            }
        }
    }

    private static boolean isOdd(final int number) {
        return (number & 1) == 1;
    }
}