diff options
Diffstat (limited to 'subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/base/itc/alg/misc/topsort/TopologicalSorting.java')
-rw-r--r-- | subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/base/itc/alg/misc/topsort/TopologicalSorting.java | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/base/itc/alg/misc/topsort/TopologicalSorting.java b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/base/itc/alg/misc/topsort/TopologicalSorting.java new file mode 100644 index 00000000..dd18e6c8 --- /dev/null +++ b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/base/itc/alg/misc/topsort/TopologicalSorting.java | |||
@@ -0,0 +1,77 @@ | |||
1 | /******************************************************************************* | ||
2 | * Copyright (c) 2010-2012, Tamas Szabo, Istvan Rath and Daniel Varro | ||
3 | * This program and the accompanying materials are made available under the | ||
4 | * terms of the Eclipse Public License v. 2.0 which is available at | ||
5 | * http://www.eclipse.org/legal/epl-v20.html. | ||
6 | * | ||
7 | * SPDX-License-Identifier: EPL-2.0 | ||
8 | *******************************************************************************/ | ||
9 | |||
10 | package tools.refinery.viatra.runtime.base.itc.alg.misc.topsort; | ||
11 | |||
12 | import java.util.HashSet; | ||
13 | import java.util.LinkedList; | ||
14 | import java.util.List; | ||
15 | import java.util.Set; | ||
16 | import java.util.Stack; | ||
17 | |||
18 | import tools.refinery.viatra.runtime.base.itc.igraph.IGraphDataSource; | ||
19 | |||
20 | /** | ||
21 | * @since 1.6 | ||
22 | */ | ||
23 | public class TopologicalSorting { | ||
24 | |||
25 | private TopologicalSorting() {/*Utility class constructor*/} | ||
26 | |||
27 | private static final class Pair<T> { | ||
28 | public T element; | ||
29 | public boolean isParent; | ||
30 | |||
31 | public Pair(final T element, final boolean isParent) { | ||
32 | this.element = element; | ||
33 | this.isParent = isParent; | ||
34 | } | ||
35 | } | ||
36 | |||
37 | /** | ||
38 | * Returns a topological ordering for the given graph data source. | ||
39 | * Output format: if there is an a -> b (transitive) reachability, then node <code>a</code> will come before node <code>b</code> in the resulting list. | ||
40 | * | ||
41 | * @param gds the graph data source | ||
42 | * @return a topological ordering | ||
43 | */ | ||
44 | public static <T> List<T> compute(final IGraphDataSource<T> gds) { | ||
45 | final Set<T> visited = new HashSet<T>(); | ||
46 | final LinkedList<T> result = new LinkedList<T>(); | ||
47 | final Stack<Pair<T>> dfsStack = new Stack<Pair<T>>(); | ||
48 | |||
49 | for (final T node : gds.getAllNodes()) { | ||
50 | if (!visited.contains(node)) { | ||
51 | dfsStack.push(new Pair<T>(node, false)); | ||
52 | } | ||
53 | |||
54 | while (!dfsStack.isEmpty()) { | ||
55 | final Pair<T> head = dfsStack.pop(); | ||
56 | final T source = head.element; | ||
57 | |||
58 | if (head.isParent) { | ||
59 | // we have already seen source, push it to the resulting stack | ||
60 | result.addFirst(source); | ||
61 | } else { | ||
62 | // first time we see source, continue with its children | ||
63 | visited.add(source); | ||
64 | dfsStack.push(new Pair<T>(source, true)); | ||
65 | |||
66 | for (final T target : gds.getTargetNodes(source).distinctValues()) { | ||
67 | if (!visited.contains(target)) { | ||
68 | dfsStack.push(new Pair<T>(target, false)); | ||
69 | } | ||
70 | } | ||
71 | } | ||
72 | } | ||
73 | } | ||
74 | |||
75 | return result; | ||
76 | } | ||
77 | } | ||