June 2018 Update

Task/Topological-sort/Kotlin/topological-sort.kotlin

@@ -0,0 +1,69 @@
+// version 1.1.51
+
+val s = "std, ieee, des_system_lib, dw01, dw02, dw03, dw04, dw05, " +
+        "dw06, dw07, dware, gtech, ramlib, std_cell_lib, synopsys"
+
+val deps = mutableListOf(
+     2 to 0, 2 to 14, 2 to 13, 2 to 4, 2 to 3, 2 to 12, 2 to 1,
+     3 to 1, 3 to 10, 3 to 11,
+     4 to 1, 4 to 10,
+     5 to 0, 5 to 14, 5 to 10, 5 to 4, 5 to 3, 5 to 1, 5 to 11,
+     6 to 1, 6 to 3, 6 to 10, 6 to 11,
+     7 to 1, 7 to 10,
+     8 to 1, 8 to 10,
+     9 to 1, 9 to 10,
+     10 to 1,
+     11 to 1,
+     12 to 0, 12 to 1,
+     13 to 1
+)
+
+class Graph(s: String, edges: List<Pair<Int,Int>>) {
+
+    val vertices = s.split(", ")
+    val numVertices = vertices.size
+    val adjacency = List(numVertices) { BooleanArray(numVertices) }
+
+    init {
+        for (edge in edges) adjacency[edge.first][edge.second] = true
+    }
+
+    fun hasDependency(r: Int, todo: List<Int>): Boolean {
+        for (c in todo) if (adjacency[r][c]) return true
+        return false
+    }
+
+    fun topoSort(): List<String>? {
+        val result = mutableListOf<String>()
+        val todo = MutableList<Int>(numVertices) { it }
+        try {
+            outer@ while(!todo.isEmpty()) {
+                for ((i, r) in todo.withIndex()) {
+                    if (!hasDependency(r, todo)) {
+                        todo.removeAt(i)
+                        result.add(vertices[r])
+                        continue@outer
+                     }
+                }
+                throw Exception("Graph has cycles")
+            }
+        }
+        catch (e: Exception) {
+            println(e)
+            return null
+        }
+        return result
+    }
+}
+
+fun main(args: Array<String>) {
+    val g = Graph(s, deps)
+    println("Topologically sorted order:")
+    println(g.topoSort())
+    println()
+    // now insert 3 to 6 at index 10 of deps
+    deps.add(10, 3 to 6)
+    val g2 = Graph(s, deps)
+    println("Following the addition of dw04 to the dependencies of dw01:")
+    println(g2.topoSort())
+}