| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.cassandra.utils; |
| |
| import java.util.ArrayList; |
| import java.util.Collections; |
| import java.util.HashMap; |
| import java.util.HashSet; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.NavigableSet; |
| import java.util.Set; |
| import java.util.TreeSet; |
| import java.util.function.Consumer; |
| |
| import com.google.common.collect.ImmutableMap; |
| import com.google.common.collect.ImmutableSet; |
| import com.google.common.collect.Ordering; |
| |
| /** |
| * A directed graph. Main usage is the {@link #findPaths(Object, Object)} method which is used to find all paths between |
| * 2 vertices. |
| */ |
| public class SimpleGraph<V> |
| { |
| private final ImmutableMap<V, ImmutableSet<V>> edges; |
| |
| private SimpleGraph(ImmutableMap<V, ImmutableSet<V>> edges) |
| { |
| if (edges == null || edges.isEmpty()) |
| throw new AssertionError("Edges empty"); |
| this.edges = edges; |
| } |
| |
| public static <T extends Comparable<T>> NavigableSet<T> sortedVertices(SimpleGraph<T> graph) |
| { |
| return new TreeSet<>(graph.vertices()); |
| } |
| |
| public static <T extends Comparable<T>> T min(SimpleGraph<T> graph) |
| { |
| return Ordering.natural().min(graph.vertices()); |
| } |
| |
| public static <T extends Comparable<T>> T max(SimpleGraph<T> graph) |
| { |
| return Ordering.natural().max(graph.vertices()); |
| } |
| |
| public boolean hasEdge(V a, V b) |
| { |
| ImmutableSet<V> matches = edges.get(a); |
| return matches != null && matches.contains(b); |
| } |
| |
| public ImmutableSet<V> vertices() |
| { |
| ImmutableSet.Builder<V> b = ImmutableSet.builder(); |
| b.addAll(edges.keySet()); |
| edges.values().forEach(b::addAll); |
| return b.build(); |
| } |
| |
| public List<List<V>> findPaths(V from, V to) |
| { |
| List<List<V>> matches = new ArrayList<>(); |
| findPaths0(Collections.singletonList(from), from, to, matches::add); |
| return matches; |
| } |
| |
| private void findPaths0(List<V> accum, V from, V to, Consumer<List<V>> onMatch) |
| { |
| ImmutableSet<V> check = edges.get(from); |
| if (check == null) |
| return; // no matches |
| for (V next : check) |
| { |
| if (accum.contains(next)) |
| return; // ignore walking recursive |
| List<V> nextAccum = new ArrayList<>(accum); |
| nextAccum.add(next); |
| if (next.equals(to)) |
| { |
| onMatch.accept(nextAccum); |
| } |
| else |
| { |
| findPaths0(nextAccum, next, to, onMatch); |
| } |
| } |
| } |
| |
| public static class Builder<V> |
| { |
| private final Map<V, Set<V>> edges = new HashMap<>(); |
| |
| public Builder<V> addEdge(V from, V to) |
| { |
| edges.computeIfAbsent(from, ignore -> new HashSet<>()).add(to); |
| return this; |
| } |
| |
| public SimpleGraph<V> build() |
| { |
| ImmutableMap.Builder<V, ImmutableSet<V>> builder = ImmutableMap.builder(); |
| for (Map.Entry<V, Set<V>> e : edges.entrySet()) |
| builder.put(e.getKey(), ImmutableSet.copyOf(e.getValue())); |
| return new SimpleGraph(builder.build()); |
| } |
| } |
| } |