Initial data commit

Task/Topological-sort/Java/topological-sort.java

@@ -0,0 +1,77 @@
+import java.util.*;
+
+public class TopologicalSort {
+
+    public static void main(String[] args) {
+        String s = "std, ieee, des_system_lib, dw01, dw02, dw03, dw04, dw05,"
+                + "dw06, dw07, dware, gtech, ramlib, std_cell_lib, synopsys";
+
+        Graph g = new Graph(s, new int[][]{
+            {2, 0}, {2, 14}, {2, 13}, {2, 4}, {2, 3}, {2, 12}, {2, 1},
+            {3, 1}, {3, 10}, {3, 11},
+            {4, 1}, {4, 10},
+            {5, 0}, {5, 14}, {5, 10}, {5, 4}, {5, 3}, {5, 1}, {5, 11},
+            {6, 1}, {6, 3}, {6, 10}, {6, 11},
+            {7, 1}, {7, 10},
+            {8, 1}, {8, 10},
+            {9, 1}, {9, 10},
+            {10, 1},
+            {11, 1},
+            {12, 0}, {12, 1},
+            {13, 1}
+        });
+
+        System.out.println("Topologically sorted order: ");
+        System.out.println(g.topoSort());
+    }
+}
+
+class Graph {
+    String[] vertices;
+    boolean[][] adjacency;
+    int numVertices;
+
+    public Graph(String s, int[][] edges) {
+        vertices = s.split(",");
+        numVertices = vertices.length;
+        adjacency = new boolean[numVertices][numVertices];
+
+        for (int[] edge : edges)
+            adjacency[edge[0]][edge[1]] = true;
+    }
+
+    List<String> topoSort() {
+        List<String> result = new ArrayList<>();
+        List<Integer> todo = new LinkedList<>();
+
+        for (int i = 0; i < numVertices; i++)
+            todo.add(i);
+
+        try {
+            outer:
+            while (!todo.isEmpty()) {
+                for (Integer r : todo) {
+                    if (!hasDependency(r, todo)) {
+                        todo.remove(r);
+                        result.add(vertices[r]);
+                         // no need to worry about concurrent modification
+                        continue outer;
+                    }
+                }
+                throw new Exception("Graph has cycles");
+            }
+        } catch (Exception e) {
+            System.out.println(e);
+            return null;
+        }
+        return result;
+    }
+
+    boolean hasDependency(Integer r, List<Integer> todo) {
+        for (Integer c : todo) {
+            if (adjacency[r][c])
+                return true;
+        }
+        return false;
+    }
+}