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src/main/java/edu/university/ecs/lab/impact/metrics/services/cyclic/GraphTraverser.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,108 @@ | ||
| package edu.university.ecs.lab.impact.metrics.services.cyclic; | ||
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| import com.google.common.collect.AbstractIterator; | ||
| import com.google.common.collect.FluentIterable; | ||
| import com.google.common.graph.Graph; | ||
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| import java.util.*; | ||
| import java.util.function.Consumer; | ||
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| /** | ||
| * Graph traverser for post order | ||
| * @param <T> Type of node | ||
| */ | ||
| @SuppressWarnings("UnstableApiUsage") | ||
| public class GraphTraverser<T> { | ||
| private record PostOrderNode<T>(T root, Iterator<T> childIterator) { | ||
| private PostOrderNode(T root, Iterator<T> childIterator) { | ||
| this.root = Objects.requireNonNull(root); | ||
| this.childIterator = Objects.requireNonNull(childIterator); | ||
| } | ||
| } | ||
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| private final class PostOrderIterator extends AbstractIterator<T> { | ||
| private final ArrayDeque<PostOrderNode<T>> stack = new ArrayDeque<>(); | ||
| private final Iterator<T> rootNodes; | ||
| private final Set<T> visitedSet; | ||
| private final Set<T> ignoredSet; | ||
| private final Consumer<T> ignoreNodeEncountered; | ||
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| public PostOrderIterator(Collection<T> roots, Set<T> ignoredNodes, Consumer<T> ignoreNodeMet) { | ||
| this.rootNodes = roots.iterator(); | ||
| this.visitedSet = new HashSet<>(graph.nodes().size()); | ||
| this.ignoredSet = ignoredNodes; | ||
| this.ignoreNodeEncountered = ignoreNodeMet; | ||
| } | ||
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| @Override | ||
| protected T computeNext() { | ||
| while (stack.isEmpty() && rootNodes.hasNext()) { | ||
| pushNodeIfUnvisited(rootNodes.next()); | ||
| } | ||
| while (!stack.isEmpty()) { | ||
| PostOrderNode<T> top = stack.getLast(); | ||
| if (top.childIterator.hasNext()) { | ||
| T child = top.childIterator.next(); | ||
| pushNodeIfUnvisited(child); | ||
| } else { | ||
| stack.removeLast(); | ||
| return top.root; | ||
| } | ||
| } | ||
| return endOfData(); | ||
| } | ||
|
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| private void pushNodeIfUnvisited(T t) { | ||
| if (ignoredSet.contains(t)) { | ||
| if (ignoreNodeEncountered != null) { | ||
| ignoreNodeEncountered.accept(t); | ||
| } | ||
| return; | ||
| } | ||
| if (!visitedSet.add(t)) { | ||
| return; | ||
| } | ||
| stack.addLast(expand(t)); | ||
| } | ||
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| private PostOrderNode<T> expand(T t) { | ||
| return new PostOrderNode<T>(t, graph.successors(t).iterator()); | ||
| } | ||
| } | ||
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| private final Graph<T> graph; | ||
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| public GraphTraverser(Graph<T> graph) { | ||
| this.graph = Objects.requireNonNull(graph); | ||
| } | ||
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| public Iterable<T> postOrderTraversal() { | ||
| return postOrderTraversal(graph.nodes()); | ||
| } | ||
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| public FluentIterable<T> postOrderTraversal(Collection<T> rootNodes) { | ||
| return postOrderTraversal(rootNodes, Collections.emptySet(), null); | ||
| } | ||
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| /** | ||
| * Does post order traversal of the (directed) graph. When a node in ignoredNodes is encountered, ignoreNodeMet is | ||
| * called | ||
| * | ||
| * @param rootNodes | ||
| * the nodes to start traversal at | ||
| * @param ignoredNodes | ||
| * nodes that will be ignored, i.e. not recursively traversed | ||
| * @param ignoredNodeMet | ||
| * might be null for no callback | ||
| * @return | ||
| */ | ||
| public FluentIterable<T> postOrderTraversal(Collection<T> rootNodes, Set<T> ignoredNodes, | ||
| Consumer<T> ignoredNodeMet) { | ||
| return new FluentIterable<T>() { | ||
| @Override | ||
| public Iterator<T> iterator() { | ||
| return new PostOrderIterator(rootNodes, ignoredNodes, ignoredNodeMet); | ||
| } | ||
| }; | ||
| } | ||
| } |
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