com.googlecode.blaisemath.graph.GraphComponents Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of blaise-graph-theory Show documentation
Graph definitions and algorithms.
There is a newer version: 4.0.8
package com.googlecode.blaisemath.graph;

/*
 * #%L
 * BlaiseGraphTheory
 * --
 * Copyright (C) 2009 - 2019 Elisha Peterson
 * --
 * Licensed 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.
 * #L%
 */

import com.google.common.collect.Sets;
import com.google.common.graph.Graph;
import com.google.common.graph.Graphs;
import com.google.errorprone.annotations.Immutable;

import java.util.Collection;
import java.util.Collections;
import java.util.Set;

/**
 * Encapsulate graph with its set of components, storing each as a separate collection of nodes and a separate graph.
 * Designed as an immutable structure, although if the underlying graph changes this class is not aware.
 *
 * @param  node type
 *
 * @author Elisha Peterson
 */
@Immutable
final class GraphComponents {

    /** What this class is modifying/describing. */
    private final Graph graph;
    /** The connected components of the graph. */
    private final Collection> components;
    /** Stored components as graphs. */
    private final Set> componentGraphs;

    /**
     * Construct components for specified graph.
     * @param graph graph
     * @param components the partition of nodes of the graph into components
     */
    public GraphComponents(Graph graph, Collection> components) {
        this.graph = graph;
        this.components = components;
        if (components.size() == 1) {
            componentGraphs = Collections.singleton(graph);
        } else {
            this.componentGraphs = Sets.newHashSet();
            for (Set c : components) {
                componentGraphs.add(Graphs.inducedSubgraph(graph, c));
            }
        }
    }

    /**
     * Return source graph
     * @return graph
     */
    public Graph graph() {
        return graph;
    }

    /**
     * Returns the number of components in the graph.
     * @return number of components
     */
    public int componentCount() {
        return components.size();
    }

    /**
     * The graph's connected components.
     * @return connected components
     */
    public Collection> components() {
        return Collections.unmodifiableCollection(components);
    }

    /**
     * The connected components of the graph, copied into new sub-graph representations.
     * @return sub-components
     */
    public Set> componentGraphs() {
        return Collections.unmodifiableSet(componentGraphs);
    }

}