一道有意思的多线程面试题 C# 代码实现
<p>文章转载自:http://www.pythonheidong.com/blog/article/2553/</p><p> </p>
<p><strong>如果你对多线程的控制不怎么了解,那么理解了这篇文章的内容也许对你有帮助。鼓励先自己动手实现一遍,做不出来在看代码。</strong></p>
<p> </p>
<h1>题目一:两个线程交替打印0~100的奇偶数</h1>
<p>这道题就是说有两个线程,一个名为偶数线程,一个名为奇数线程,偶数线程只打印偶数,奇数线程只打印奇数,两个线程按顺序交替打印。<strong>本文重点不是说的这道题,这道题是下面那道题的简单版本,用来做个过渡。</strong></p>
<p>效果图:</p>
<p><div align="center"></div></p>
<p>此题焦点点就是如何控制多线程的执行顺序,我们知道C#的System.Threading命名空间给开发者提供了控制线程相关的对象,线程同步常用对象有:Semaphore,ManualResetEvent,AutoResetEvent,这里我用AutoResetEvent来实现,代码如下:</p>
<div align="center"></div><div align="center"></div>
public class ThreadExample
{
/// <summary>
/// 两个线程交替打印0~100的奇偶数
/// </summary>
public static void PrintOddEvenNumber()
{
var work = new TheadWorkTest();
var thread1 = new Thread(work.PrintOddNumer) { Name = "奇数线程" };
var thread2 = new Thread(work.PrintEvenNumber) { Name = "偶数线程" };
thread1.Start();
thread2.Start();
}
}
public class TheadWorkTest
{
private static readonly AutoResetEvent oddAre = new AutoResetEvent(false);
private static readonly AutoResetEvent evenAre = new AutoResetEvent(false);
public void PrintOddNumer()
{
oddAre.WaitOne();
for (var i = 0; i < 100; i++)
{
if (i % 2 != 1) continue;
Console.WriteLine($"{Thread.CurrentThread.Name}:{i}");
evenAre.Set();
oddAre.WaitOne();
}
}
public void PrintEvenNumber()
{
for (var i = 0; i < 100; i++)
{
if (i % 2 != 0) continue;
Console.WriteLine($"{Thread.CurrentThread.Name}:{i}");
oddAre.Set();
evenAre.WaitOne();
}
}
}
View Code
<p>我这里是两个线程调用不同的方法实现,可读性会好点,如果只调用一个同样的方法你们会怎么实现呢?</p>
<h1>题目二:通过N个线程顺序循环打印0~100</h1>
<p>这篇文章主要是说这道题,此题据称是阿里的面试题,具体效果如下:</p>
<code>通过N个线程顺序循环打印从0至100,如给定N=3则输出:
<div align="center"></div><br></code>
<p> 这个题开始真没想出来,后来无意在github上有人用Java做出了答案,看到使用了Semaphore去控制,我就用C#代码做了下,代码如下:</p>
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public class ThreadExample
{
/// <summary>
/// N个线程顺序循环打印从0至100
/// </summary>
/// <param name="n"></param>
public static void PrintNumber(int n = 3)
{
var work = new TheadWorkTest { Semaphores = new Semaphore };
for (var i = 0; i < n; i++)
{
work.Semaphores = new Semaphore(1, 1);
if (i != n - 1)
work.Semaphores.WaitOne();
}
for (var i = 0; i < n; i++)
{
new Thread(work.PrintNumber) { Name = "线程" + i }.Start(i);
}
}
}
public class TheadWorkTest
{
public Semaphore[] Semaphores { get; set; }
public static int index;
public void PrintNumber(object c)
{
var i = Convert.ToInt32(c);
var preSemaphore = i == 0 ? Semaphores : Semaphores;
var curSemaphore = Semaphores;
while (true)
{
preSemaphore.WaitOne();
Interlocked.Increment(ref index);
if (index > 99)
return;
Console.WriteLine($"{Thread.CurrentThread.Name}:{index}");
curSemaphore.Release();
}
}
}
View Code
<p> </p>
<p>如果现实面试我第一次碰上了这样的题目,估计是答不上来了,那么你们以为出这样难度面试题的公司月薪给多少K符合?</p>
<p>完整代码:https://github.com/Ax0ne/Example.Leetcode/blob/master/src/Example.Leetcode/Problems/ThreadExample.cs欢迎star哟,后面会陆续添加一些有意思的题目代码。</p>
<p>博友们还能有不同的实现方式吗 ? ^_^</p>
<p>文章转载自:http://www.pythonheidong.com/blog/article/2553/</p><br>来源:<a href="https://www.cnblogs.com/xiongbatianxiaskjdskjdksjdskdtuti/p/11356741.html" target="_blank">https://www.cnblogs.com/xiongbatianxiaskjdskjdksjdskdtuti/p/11356741.html</a>
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