三个线程分别打印 A，B，C，要求这三个线程一起运行，打印 n 次，输出形如“ABCABCABC....”的字符串

using System;
using System.Threading;

class PrintThread
{
    private string text;
    private int count;
    private Semaphore semaphore;
    private Semaphore nextSemaphore;

    public PrintThread(string text, int count, Semaphore semaphore, Semaphore nextSemaphore)
    {
        this.text = text;
        this.count = count;
        this.semaphore = semaphore;
        this.nextSemaphore = nextSemaphore;
    }

    public void Run()
    {
        for (int i = 0; i < count; i++)
        {
            semaphore.WaitOne();  // 等待信号量
            Console.Write(text);
            nextSemaphore.Release();  // 释放下一个线程的信号量
        }
    }
}

class Program
{
    static void Main(string[] args)
    {
        Semaphore semaphoreA = new Semaphore(1, 1);
        Semaphore semaphoreB = new Semaphore(0, 1);
        Semaphore semaphoreC = new Semaphore(0, 1);

        int n = 10;  // 打印 n 次
        PrintThread threadA = new PrintThread("A", n, semaphoreA, semaphoreB);
        PrintThread threadB = new PrintThread("B", n, semaphoreB, semaphoreC);
        PrintThread threadC = new PrintThread("C", n, semaphoreC, semaphoreA);

        Thread t1 = new Thread(threadA.Run);
        Thread t2 = new Thread(threadB.Run);
        Thread t3 = new Thread(threadC.Run);

        t1.Start();
        t2.Start();
        t3.Start();

        t1.Join();
        t2.Join();
        t3.Join();
    }
}