Updates the initialization of lists and dictionaries throughout the codebase

Add tests for `AStar` and related classes to validate A* algorithm functionality.

Author: kamikkels

Algorithms.Tests/Graph/BellmanFordTests.cs

@@ -35,7 +35,7 @@ public void CorrectDistancesTest()
             { vertex5, -4 }
         };
 
-        var bellmanFord = new BellmanFord<int>(graph, new Dictionary<Vertex<int>, double>(), new Dictionary<Vertex<int>, Vertex<int>?>());
+        var bellmanFord = new BellmanFord<int>(graph, [], []);
 
         var calculatedDistances = bellmanFord.Run(vertex1);
 
@@ -61,7 +61,7 @@ public void NegativeWeightCycleTest()
         graph.AddEdge(vertex2, vertex3, -2);
         graph.AddEdge(vertex3, vertex1, -3);
 
-        var bellmanFord = new BellmanFord<int>(graph, new Dictionary<Vertex<int>, double>(), new Dictionary<Vertex<int>, Vertex<int>?>());
+        var bellmanFord = new BellmanFord<int>(graph, [], []);
 
         Action action = () => bellmanFord.Run(vertex1);
 

Algorithms.Tests/Numeric/AutomorphicNumberTests.cs

@@ -55,21 +55,21 @@ public void TestInvalidAutomorphicNumbers(int number)
     [TestCase(1, 100)]
     public void TestAutomorphicNumberSequence(int lower, int upper)
     {
-        List<long> automorphicList = new() { 1, 5, 6, 25, 76 };
+        List<long> automorphicList = [1, 5, 6, 25, 76];
         Assert.That(AutomorphicNumber.GetAutomorphicNumbers(lower, upper), Is.EqualTo(automorphicList));
     }
 
     [TestCase(8, 12)]
     public void TestNoAutomorphicNumberInTheSequence(int lower, int upper)
     {
-        List<long> automorphicList = new();
+        List<long> automorphicList = [];
         Assert.That(AutomorphicNumber.GetAutomorphicNumbers(lower, upper), Is.EqualTo(automorphicList));
     }
 
     [TestCase(25, 25)]
     public void TestAutomorphicNumberSequenceSameBounds(int lower, int upper)
     {
-        List<long> automorphicList = new() { 25 };
+        List<long> automorphicList = [25];
         Assert.That(AutomorphicNumber.GetAutomorphicNumbers(lower, upper), Is.EqualTo(automorphicList));
     }
 

Algorithms.Tests/Other/KochSnowflakeTest.cs

@@ -8,7 +8,7 @@ public static class KochSnowflakeTest
     [Test]
     public static void TestIterateMethod()
     {
-        List<Vector2> vectors = new() { new Vector2(0, 0), new Vector2(1, 0) };
+        List<Vector2> vectors = [new Vector2(0, 0), new Vector2(1, 0)];
         List<Vector2> result = KochSnowflake.Iterate(vectors, 1);
         result[0].Should().Be(new Vector2(0, 0));
         result[1].Should().Be(new Vector2((float)1 / 3, 0));

Algorithms.Tests/Search/AStarTests.cs

@@ -0,0 +1,106 @@
+
+using System.Reflection;
+
+using Algorithms.Search.AStar;
+
+namespace Algorithms.Tests.Search;
+
+public static class AStarTests
+{
+    [Test]
+    public static void ResetNodes_ResetsAllNodeProperties()
+    {
+        var node = new Node(new VecN(0, 0), true, 1.0)
+        {
+            CurrentCost = 5,
+            EstimatedCost = 10,
+            Parent = new Node(new VecN(1, 1), true, 1.0),
+            State = NodeState.Closed
+        };
+        var nodes = new List<Node> { node };
+
+        AStar.ResetNodes(nodes);
+
+        node.CurrentCost.Should().Be(0);
+        node.EstimatedCost.Should().Be(0);
+        node.Parent.Should().BeNull();
+        node.State.Should().Be(NodeState.Unconsidered);
+    }
+
+    [Test]
+    public static void GeneratePath_ReturnsPathFromTargetToRoot()
+    {
+        var start = new Node(new VecN(0, 0), true, 1.0);
+        var mid = new Node(new VecN(1, 0), true, 1.0) { Parent = start };
+        var end = new Node(new VecN(2, 0), true, 1.0) { Parent = mid };
+
+        var path = AStar.GeneratePath(end);
+
+        path.Should().HaveCount(3);
+        path[0].Should().BeSameAs(start);
+        path[1].Should().BeSameAs(mid);
+        path[2].Should().BeSameAs(end);
+    }
+
+    [Test]
+    public static void Compute_ReturnsEmptyList_WhenNoPathExists()
+    {
+        var start = new Node(new VecN(0, 0), true, 1.0);
+        var end = new Node(new VecN(1, 0), true, 1.0);
+        start.ConnectedNodes = [];
+        end.ConnectedNodes = [];
+
+        var path = AStar.Compute(start, end);
+
+        path.Should().BeEmpty();
+    }
+
+    [Test]
+    public static void Compute_ReturnsPath_WhenPathExists()
+    {
+        var start = new Node(new VecN(0, 0), true, 1.0);
+        var mid = new Node(new VecN(1, 0), true, 1.0);
+        var end = new Node(new VecN(2, 0), true, 1.0);
+
+        start.ConnectedNodes = [mid];
+        mid.ConnectedNodes = [end];
+        end.ConnectedNodes = [];
+
+        var path = AStar.Compute(start, end);
+
+        path.Should().NotBeEmpty();
+        path[0].Should().Be(start);
+        path[^1].Should().Be(end);
+    }
+
+    [Test]
+    public static void VecN_Equality_WorksAsExpected()
+    {
+        var a = new VecN(1, 2);
+        var b = new VecN(1, 2);
+        var c = new VecN(2, 1);
+
+        a.Equals(b).Should().BeTrue();
+        a.Equals(c).Should().BeFalse();
+    }
+
+    [Test]
+    public static void AddOrUpdateConnected_ThrowsPathfindingException_OnSelfReference()
+    {
+        var node = new Node(new VecN(0, 0), true, 1.0);
+        node.ConnectedNodes = [node];
+        node.State = NodeState.Open;
+
+        var queue = new PriorityQueue<Node>();
+
+        Action act = () => {
+            // Directly call the private method using reflection, otherwise we can't test this case
+            var method = typeof(AStar).GetMethod("AddOrUpdateConnected", BindingFlags.NonPublic | BindingFlags.Static);
+            method!.Invoke(null, [node, node, queue]);
+        };
+
+        act.Should().Throw<TargetInvocationException>()
+            .WithInnerException<PathfindingException>()
+            .WithMessage("*same node twice*");
+    }
+}

Algorithms/Encoders/FeistelCipher.cs

@@ -118,7 +118,7 @@ public string Decode(string text, uint key)
     // the last block is extended up to 8 bytes if the tail of the text is smaller than 8 bytes
     private static List<ulong> SplitTextToBlocks(string text)
     {
-        List<ulong> blocksListPlain = new();
+        List<ulong> blocksListPlain = [];
         byte[] textArray = Encoding.ASCII.GetBytes(text);
         int offset = 8;
         for (int i = 0; i < text.Length; i += 8)
@@ -139,7 +139,7 @@ private static List<ulong> SplitTextToBlocks(string text)
     // convert the encoded text to the set of ulong values (blocks for decoding)
     private static List<ulong> GetBlocksFromEncodedText(string text)
     {
-        List<ulong> blocksListPlain = new();
+        List<ulong> blocksListPlain = [];
         for (int i = 0; i < text.Length; i += 16)
         {
             ulong block = Convert.ToUInt64(text.Substring(i, 16), 16);

Algorithms/Graph/BreadthFirstSearch.cs

@@ -18,7 +18,7 @@ public class BreadthFirstSearch<T> : IGraphSearch<T> where T : IComparable<T>
     /// <param name="action">Action that needs to be executed on each graph vertex.</param>
     public void VisitAll(IDirectedWeightedGraph<T> graph, Vertex<T> startVertex, Action<Vertex<T>>? action = default)
     {
-        Bfs(graph, startVertex, action, new HashSet<Vertex<T>>());
+        Bfs(graph, startVertex, action, []);
     }
 
     /// <summary>

Algorithms/Graph/DepthFirstSearch.cs

@@ -18,7 +18,7 @@ public class DepthFirstSearch<T> : IGraphSearch<T> where T : IComparable<T>
     /// <param name="action">Action that needs to be executed on each graph vertex.</param>
     public void VisitAll(IDirectedWeightedGraph<T> graph, Vertex<T> startVertex, Action<Vertex<T>>? action = default)
     {
-        Dfs(graph, startVertex, action, new HashSet<Vertex<T>>());
+        Dfs(graph, startVertex, action, []);
     }
 
     /// <summary>

Algorithms/Graph/Kosaraju.cs

@@ -74,9 +74,9 @@ public static void Assign(Vertex<T> v, Vertex<T> root, IDirectedWeightedGraph<T>
     /// <returns>A dictionary that assigns to each vertex a root vertex of the SCC they belong. </returns>
     public static Dictionary<Vertex<T>, Vertex<T>> GetRepresentatives(IDirectedWeightedGraph<T> graph)
     {
-        HashSet<Vertex<T>> visited = new HashSet<Vertex<T>>();
+        HashSet<Vertex<T>> visited = [];
         Stack<Vertex<T>> reversedL = new Stack<Vertex<T>>();
-        Dictionary<Vertex<T>, Vertex<T>> representatives = new Dictionary<Vertex<T>, Vertex<T>>();
+        Dictionary<Vertex<T>, Vertex<T>> representatives = [];
 
         foreach (var v in graph.Vertices)
         {
@@ -105,7 +105,7 @@ public static Dictionary<Vertex<T>, Vertex<T>> GetRepresentatives(IDirectedWeigh
     public static IEnumerable<Vertex<T>>[] GetScc(IDirectedWeightedGraph<T> graph)
     {
         var representatives = GetRepresentatives(graph);
-        Dictionary<Vertex<T>, List<Vertex<T>>> scc = new Dictionary<Vertex<T>, List<Vertex<T>>>();
+        Dictionary<Vertex<T>, List<Vertex<T>>> scc = [];
         foreach (var kv in representatives)
         {
             // Assign all vertex (key) that have the seem root (value) to a single list.
@@ -115,7 +115,7 @@ public static IEnumerable<Vertex<T>>[] GetScc(IDirectedWeightedGraph<T> graph)
             }
             else
             {
-                scc.Add(kv.Value, new List<Vertex<T>> { kv.Key });
+                scc.Add(kv.Value, [kv.Key]);
             }
         }
 

Algorithms/Graph/MinimumSpanningTree/Kruskal.cs

@@ -108,7 +108,7 @@ public static Dictionary<int, float>[] Solve(Dictionary<int, float>[] adjacencyL
         var mst = new Dictionary<int, float>[numNodes];
         for (var i = 0; i < numNodes; i++)
         {
-            mst[i] = new Dictionary<int, float>();
+            mst[i] = [];
         }
 
         foreach (var (node1, node2) in edges)

Algorithms/Knapsack/BranchAndBoundKnapsackSolver.cs

@@ -102,7 +102,7 @@ public T[] Solve(T[] items, int capacity, Func<T, int> weightSelector, Func<T, d
     // determine items taken based on the path
     private static T[] GetItemsFromPath(T[] items, BranchAndBoundNode lastNodeOfPath)
     {
-        List<T> takenItems = new();
+        List<T> takenItems = [];
 
         // only bogus initial node has no parent
         for (var current = lastNodeOfPath; current.Parent is not null; current = current.Parent)