project restructured

Aufgaben/DuplicateCheckerLib/DuplicateCheckerLib/DuplicateCheckerLib.sln

@@ -0,0 +1,25 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 16
+VisualStudioVersion = 16.0.28803.352
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DuplicateCheckerLib", "DuplicateCheckerLib\DuplicateCheckerLib.csproj", "{17DFFFC5-D41F-4C9B-99AD-3A14920152DB}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{17DFFFC5-D41F-4C9B-99AD-3A14920152DB}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{17DFFFC5-D41F-4C9B-99AD-3A14920152DB}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{17DFFFC5-D41F-4C9B-99AD-3A14920152DB}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{17DFFFC5-D41F-4C9B-99AD-3A14920152DB}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {A67D4C42-99C6-4966-8AAB-083C0B66A643}
+	EndGlobalSection
+EndGlobal

Aufgaben/DuplicateCheckerLib/DuplicateCheckerLib/DuplicateCheckerLib/DuplicateChecker.cs

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+using System.Collections.Generic;
+
+namespace DuplicateCheckerLib {
+    public class DuplicateChecker {
+        public IEnumerable<IEntity> FindDuplicates(IEnumerable<IEntity> list) {
+            var hashSet = new HashSet<IEntity>();
+            var ret = new List<IEntity>();
+            foreach (var item in list) {
+                if (!hashSet.Add(item)) {
+                    ret.Add(item);
+                }
+            }
+
+            return ret;
+        }
+    }
+}

Aufgaben/DuplicateCheckerLib/DuplicateCheckerLib/DuplicateCheckerLib/DuplicateCheckerLib.csproj

@@ -0,0 +1,7 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netstandard2.0</TargetFramework>
+  </PropertyGroup>
+
+</Project>

Aufgaben/DuplicateCheckerLib/DuplicateCheckerLib/DuplicateCheckerLib/IEntity.cs

@@ -0,0 +1,8 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace DuplicateCheckerLib {
+    public interface IEntity {
+    }
+}