Priority Queue

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-dotnet@v1
         with:
-          dotnet-version: '6.x'
+          dotnet-version: '7.x'
       - name: Build
         run: for dir in */; do cd $dir; for sln in *.sln; do dotnet build $sln; cd ..; done; done
         shell: bash

PriorityQueue/PriorityQueue.Tests/PriorityQueue.Tests.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net7.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+
+        <IsPackable>false</IsPackable>
+
+        <RootNamespace>PiorityQueue.Tests</RootNamespace>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.2" />
+        <PackageReference Include="NUnit" Version="3.13.3" />
+        <PackageReference Include="NUnit3TestAdapter" Version="4.2.1" />
+        <PackageReference Include="NUnit.Analyzers" Version="3.3.0" />
+        <PackageReference Include="coverlet.collector" Version="3.1.2" />
+    </ItemGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\PriorityQueue\PriorityQueue.csproj" />
+    </ItemGroup>
+
+</Project>

PriorityQueue/PriorityQueue.Tests/PriorityQueueTests.cs

@@ -0,0 +1,90 @@
+namespace PriorityQueue.Tests;
+
+using PriorityQueue;
+
+public class Tests
+{
+    private PriorityQueue<int> _priorityQueue = new ();
+
+    [SetUp]
+    public void Setup()
+    {
+        _priorityQueue = new PriorityQueue<int>();
+        var tasks = new Task[10];
+
+        for (var i = 0; i < 10; i++)
+        {
+            var priority = i;
+            tasks[i] = Task.Run(() => EnqueueValues(priority));
+        }
+
+        Task.WaitAll(tasks);
+    }
+
+    [Test]
+    public void DequeueShouldReturnFirstAddedValue()
+    {
+        var actualValue = _priorityQueue.Dequeue();
+        Assert.That(actualValue, Is.EqualTo(0));
+    }
+
+    [Test]
+    public void TestNumberOfElements()
+    {
+        Assert.That(_priorityQueue.Size, Is.EqualTo(100));
+    }
+
+    [Test]
+    public void DequeueShouldReturnAllElementsInCorrectOrder()
+    {
+        for (var i = 0; i < 10; i++)
+        {
+            for (var j = 0; j < 10; j++)
+            {
+                var actualValue = _priorityQueue.Dequeue();
+                Assert.That(actualValue, Is.EqualTo(j));
+            }
+        }
+    }
+
+    [Test]
+    public void ThreadsShouldWaitIfThereIsNoElementsInTheQueue()
+    {
+        for (var i = 0; i < 10; i++)
+        {
+            for (var j = 0; j < 10; j++)
+            {
+                var actualValue = _priorityQueue.Dequeue();
+            }
+        }
+
+        var tasks = new Task[5];
+        for (var taskNumber = 0; taskNumber < 5; taskNumber++)
+        {
+            tasks[taskNumber] = Task.Run(() => DequeueValueAndCompare(5));
+        }
+
+        for (var i = 0; i < 5; i++)
+        {
+            _priorityQueue.Enqueue(i, i);
+        }
+
+        Task.WaitAll(tasks);
+
+        Assert.That(_priorityQueue.Size, Is.EqualTo(0));
+    }
+
+    private void DequeueValueAndCompare(int expectedValue)
+    {
+        var actualValue = _priorityQueue.Dequeue();
+        Assert.That(actualValue, Is.LessThan(expectedValue));
+    }
+
+    private void EnqueueValues(int priority)
+    {
+        for (var value = 0; value < 10; value++)
+        {
+            _priorityQueue.Enqueue(value, priority);
+        }
+    }
+}

PriorityQueue/PriorityQueue.Tests/Usings.cs

@@ -0,0 +1 @@
+global using NUnit.Framework;

PriorityQueue/PriorityQueue.sln

@@ -0,0 +1,22 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "PriorityQueue", "PriorityQueue\PriorityQueue.csproj", "{A729599D-41D7-4A91-A884-3A50422DDC7E}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "PriorityQueue.Tests", "PriorityQueue.Tests\PriorityQueue.Tests.csproj", "{EEB7DAD5-E485-455F-A363-5DD9765E2AE4}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{A729599D-41D7-4A91-A884-3A50422DDC7E}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{A729599D-41D7-4A91-A884-3A50422DDC7E}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{A729599D-41D7-4A91-A884-3A50422DDC7E}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{A729599D-41D7-4A91-A884-3A50422DDC7E}.Release|Any CPU.Build.0 = Release|Any CPU
+		{EEB7DAD5-E485-455F-A363-5DD9765E2AE4}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{EEB7DAD5-E485-455F-A363-5DD9765E2AE4}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{EEB7DAD5-E485-455F-A363-5DD9765E2AE4}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{EEB7DAD5-E485-455F-A363-5DD9765E2AE4}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal

PriorityQueue/PriorityQueue/PriorityQueue.cs

@@ -0,0 +1,90 @@
+namespace PriorityQueue;
+
+using System.Linq;
+
+/// <summary>
+/// Thread safe priority queue.
+/// </summary>
+/// <typeparam name="TValue">Type of queue elements.</typeparam>
+public class PriorityQueue<TValue>
+{
+    private List<QueueElement<TValue>> _queueElementList = new ();
+
+    /// <summary>
+    /// Gets count of elements in the queue.
+    /// </summary>
+    public int Size => _queueElementList.Count;
+
+    /// <summary>
+    /// Enqueues value with given priority.
+    /// </summary>
+    /// <param name="value">Element value.</param>
+    /// <param name="priority">Priority of the element.</param>
+    public void Enqueue(TValue value, int priority)
+    {
+        lock (_queueElementList)
+        {
+            var newElement = new QueueElement<TValue>(value, priority);
+            _queueElementList.Add(newElement);
+
+            Monitor.PulseAll(_queueElementList);
+        }
+    }
+
+    /// <summary>
+    /// Gets element with the highest priority and removes it from the queue.
+    /// </summary>
+    /// <returns></returns>
+    public TValue Dequeue()
+    {
+        lock (_queueElementList)
+        {
+            while (Size == 0)
+            {
+                Monitor.Wait(_queueElementList);
+            }
+
+            return GetAndRemove().Value;
+        }
+    }
+
+    private QueueElement<TValue> GetAndRemove()
+    {
+        var maxElement = _queueElementList.Max() ?? throw new ArgumentNullException();
+        _queueElementList.Remove(maxElement);
+        return maxElement;
+    }
+
+    /// <summary>
+    /// Class for elements of the queue.
+    /// </summary>
+    /// <typeparam name="TValue">Elements value type.</typeparam>
+    private class QueueElement<TValue> : IComparable<QueueElement<TValue>>
+    {
+        /// <summary>
+        /// Element priority.
+        /// </summary>
+        public int Priority { get; }
+
+        /// <summary>
+        /// Element value.
+        /// </summary>
+        public TValue Value { get; }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="QueueElement"/> class.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="priority"></param>
+        public QueueElement(TValue value, int priority)
+        {
+            Priority = priority;
+            Value = value;
+        }
+
+        public int CompareTo(QueueElement<TValue>? other)
+        {
+            return this.Priority.CompareTo((other ?? throw new ArgumentNullException()).Priority);
+        }
+    }
+}

PriorityQueue/PriorityQueue/PriorityQueue.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net7.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+        <RootNamespace>Queue</RootNamespace>
+    </PropertyGroup>
+
+</Project>