Data commit

Task/Tarjan/Kotlin/tarjan.kotlin

@@ -0,0 +1,75 @@
+// version 1.1.3
+
+import java.util.Stack
+
+typealias Nodes = List<Node>
+
+class Node(val n: Int) {
+    var index   = -1  // -1 signifies undefined
+    var lowLink = -1
+    var onStack = false
+
+    override fun toString()  = n.toString()
+}
+
+class DirectedGraph(val vs: Nodes, val es: Map<Node, Nodes>)
+
+fun tarjan(g: DirectedGraph): List<Nodes> {
+    val sccs = mutableListOf<Nodes>()
+    var index = 0
+    val s = Stack<Node>()
+
+    fun strongConnect(v: Node) {
+        // Set the depth index for v to the smallest unused index
+        v.index = index
+        v.lowLink = index
+        index++
+        s.push(v)
+        v.onStack = true
+
+        // consider successors of v
+        for (w in g.es[v]!!) {
+            if (w.index < 0) {
+                // Successor w has not yet been visited; recurse on it
+                strongConnect(w)
+                v.lowLink = minOf(v.lowLink, w.lowLink)
+            }
+            else if (w.onStack) {
+                // Successor w is in stack s and hence in the current SCC
+                v.lowLink = minOf(v.lowLink, w.index)
+            }
+        }
+
+        // If v is a root node, pop the stack and generate an SCC
+        if (v.lowLink == v.index) {
+            val scc = mutableListOf<Node>()
+            do {
+                val w = s.pop()
+                w.onStack = false
+                scc.add(w)
+            }
+            while (w != v)
+            sccs.add(scc)
+        }
+    }
+
+    for (v in g.vs) if (v.index < 0) strongConnect(v)
+    return sccs
+}
+
+fun main(args: Array<String>) {
+    val vs = (0..7).map { Node(it) }
+    val es = mapOf(
+        vs[0] to listOf(vs[1]),
+        vs[2] to listOf(vs[0]),
+        vs[5] to listOf(vs[2], vs[6]),
+        vs[6] to listOf(vs[5]),
+        vs[1] to listOf(vs[2]),
+        vs[3] to listOf(vs[1], vs[2], vs[4]),
+        vs[4] to listOf(vs[5], vs[3]),
+        vs[7] to listOf(vs[4], vs[7], vs[6])
+    )
+    val g = DirectedGraph(vs, es)
+    val sccs = tarjan(g)
+    println(sccs.joinToString("\n"))
+}