Data commit

Task/Tarjan/C-sharp/tarjan.cs

@@ -0,0 +1,73 @@
+using System;
+using System.Collections.Generic;
+
+class Node
+{
+    public int LowLink { get; set; }
+    public int Index { get; set; }
+    public int N { get; }
+
+    public Node(int n)
+    {
+        N = n;
+        Index = -1;
+        LowLink = 0;
+    }
+}
+
+class Graph
+{
+    public HashSet<Node> V { get; }
+    public Dictionary<Node, HashSet<Node>> Adj { get; }
+
+    /// <summary>
+    /// Tarjan's strongly connected components algorithm
+    /// </summary>
+    public void Tarjan()
+    {
+        var index = 0; // number of nodes
+        var S = new Stack<Node>();
+
+        Action<Node> StrongConnect = null;
+        StrongConnect = (v) =>
+        {
+            // Set the depth index for v to the smallest unused index
+            v.Index = index;
+            v.LowLink = index;
+
+            index++;
+            S.Push(v);
+
+            // Consider successors of v
+            foreach (var w in Adj[v])
+                if (w.Index < 0)
+                {
+                    // Successor w has not yet been visited; recurse on it
+                    StrongConnect(w);
+                    v.LowLink = Math.Min(v.LowLink, w.LowLink);
+                }
+                else if (S.Contains(w))
+                    // Successor w is in stack S and hence in the current SCC
+                    v.LowLink = Math.Min(v.LowLink, w.Index);
+
+            // If v is a root node, pop the stack and generate an SCC
+            if (v.LowLink == v.Index)
+            {
+                Console.Write("SCC: ");
+
+                Node w;
+                do
+                {
+                    w = S.Pop();
+                    Console.Write(w.N + " ");
+                } while (w != v);
+
+                Console.WriteLine();
+            }
+        };
+
+        foreach (var v in V)
+            if (v.Index < 0)
+                StrongConnect(v);
+    }
+}