Create a digraph base class

Author: Kapil Borle

Engine/Helper.cs

@@ -3557,81 +3557,58 @@ public object VisitUsingExpression(UsingExpressionAst usingExpressionAst)
     }
 
     /// Class to represent a directed graph
-    public class Digraph<T>
+    public class Digraph
     {
-        public int NumVertices
-        {
-            get { return graph.Count; }
-        }
-
         private List<List<int>> graph;
-        private Dictionary<T, int> vertexIndexMap;
-
 
-        private int GetIndex(T vertex)
+        public Digraph()
         {
-            int idx;
-            return vertexIndexMap.TryGetValue(vertex, out idx) ? idx : -1;
+            graph = new List<List<int>> ();
         }
 
-        public IEnumerable<T> GetNeighbors(T vertex)
+        public int GetNumVertices()
         {
-            ValidateVertexArgument(vertex);
-            var idx = GetIndex(vertex);
-            var idxVertexMap = vertexIndexMap.ToDictionary(x => x.Value, x => x.Key);
-            foreach (var neighbor in graph[idx])
-            {
-                yield return idxVertexMap[neighbor];
-            }
+            return graph.Count;
         }
 
-        public int GetNumNeighbors(T vertex)
+        public int GetNumNeighbors(int vertex)
         {
-            ValidateVertexArgument(vertex);
-            return graph[GetIndex(vertex)].Count;
+            return GetNeighbors(vertex).Count();
         }
 
-        public Digraph()
+        public IEnumerable<int> GetNeighbors(int vertex)
         {
-            graph = new List<List<int>> ();
-            vertexIndexMap = new Dictionary<T, int>();
+            ValidateVertex(vertex);
+            return graph[vertex];
         }
 
-        public void AddVertex(T vertex)
+        public bool ContainsVertex(int vertex)
         {
-            if (vertex == null)
-            {
-                throw new ArgumentNullException("vertex");
-            }
-
-            if (GetIndex(vertex) != -1)
-            {
-                throw new ArgumentException("Vertex already present! Cannot add it to the Digraph", "vertex");
-            }
+            return vertex >= 0 && vertex < graph.Count;
+        }
 
-            vertexIndexMap.Add(vertex, graph.Count);
+        public void AddVertex()
+        {
             graph.Add(new List<int>());
         }
 
-        public void AddEdge(T fromVertex, T toVertex)
+        public void AddEdge(int fromVertex, int toVertex)
         {
-            ValidateVertexArgument(fromVertex);
-            ValidateVertexArgument(toVertex);
-
-            var toIdx = GetIndex(toVertex);
-            var fromVertexList = graph[GetIndex(fromVertex)];
-            if (!fromVertexList.Contains(toIdx))
+            ValidateVertex(fromVertex);
+            ValidateVertex(toVertex);
+            if (graph[fromVertex].Contains(toVertex))
             {
-                fromVertexList.Add(toIdx);
+                throw new ArgumentException(String.Format("Edge from {0} to {1} already present", fromVertex, toVertex));
             }
+            graph[fromVertex].Add(toVertex);
         }
 
-        public bool IsConnected(T vertex1, T vertex2)
+        public bool IsConnected(int vertex1, int vertex2)
         {
-            ValidateVertexArgument(vertex1);
-            ValidateVertexArgument(vertex2);
+            ValidateVertex(vertex1);
+            ValidateVertex(vertex2);
             var visited = new bool[graph.Count];
-            return IsConnected(GetIndex(vertex1), GetIndex(vertex2), ref visited);
+            return IsConnected(vertex1, vertex2, ref visited);
         }
 
         private bool IsConnected(int fromIdx, int toIdx, ref bool[] visited)
@@ -3659,26 +3636,12 @@ private bool IsConnected(int fromIdx, int toIdx, ref bool[] visited)
             return isConnected;
         }
 
-        private void ValidateNotNull(T vertex)
+        private void ValidateVertex(int vertex)
         {
-            if (vertex == null)
-            {
-                throw new ArgumentNullException("vertex");
-            }
-        }
-
-        private void ValidateVertexPresence(T vertex)
-        {
-            if (GetIndex(vertex) == -1)
+            if (!ContainsVertex(vertex))
             {
                 throw new ArgumentOutOfRangeException("vertex not present in the Digraph.", "vertex");
             }
         }
-
-        private void ValidateVertexArgument(T vertex)
-        {
-            ValidateNotNull(vertex);
-            ValidateVertexPresence(vertex);
-        }
     }
 }

Tests/Engine/Helpers.tests.ps1

@@ -2,30 +2,26 @@ Import-Module PSScriptAnalyzer
 
 Describe "Test Directed Graph" {
     Context "When a graph is created" {
-        $digraph = New-Object -TypeName 'Microsoft.Windows.PowerShell.ScriptAnalyzer.DiGraph[string]'
-        $digraph.AddVertex('v1');
-        $digraph.AddVertex('v2');
-        $digraph.AddVertex('v3');
-        $digraph.AddVertex('v4');
-        $digraph.AddVertex('v5');
+        $digraph = New-Object -TypeName 'Microsoft.Windows.PowerShell.ScriptAnalyzer.DiGraph'
+        0..4 | ForEach-Object {$digraph.AddVertex()}
 
-        $digraph.AddEdge('v1', 'v2');
-        $digraph.AddEdge('v1', 'v5');
-        $digraph.AddEdge('v2', 'v4');
+        $digraph.AddEdge(0, 1);
+        $digraph.AddEdge(0, 4);
+        $digraph.AddEdge(1, 3);
 
         It "correctly adds the vertices" {
-            $digraph.NumVertices | Should Be 5
+            $digraph.GetNumVertices() | Should Be 5
         }
 
         It "correctly adds the edges" {
-            $digraph.GetNumNeighbors('v1') | Should Be 2
-            $neighbors = $digraph.GetNeighbors('v1')
-            $neighbors -contains 'v2' | Should Be $true
-            $neighbors -contains 'v5' | Should Be $true
+            $digraph.GetNumNeighbors(0) | Should Be 2
+            $neighbors = $digraph.GetNeighbors(0)
+            $neighbors -contains 1 | Should Be $true
+            $neighbors -contains 4 | Should Be $true
         }
 
         It "finds the connection" {
-            $digraph.IsConnected('v1', 'v4') | Should Be $true
+            $digraph.IsConnected(0, 3) | Should Be $true
         }
     }
 }