com.google.common.graph.AbstractNetwork Maven / Gradle / Ivy
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/*
* Copyright (C) 2016 The Guava Authors
*
* 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.
*/
package com.google.common.graph;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.graph.GraphConstants.ENDPOINTS_MISMATCH;
import static com.google.common.graph.GraphConstants.MULTIPLE_EDGES_CONNECTING;
import static java.util.Collections.unmodifiableSet;
import com.google.common.annotations.Beta;
import com.google.common.base.Function;
import com.google.common.base.Predicate;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterators;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import com.google.common.math.IntMath;
import java.util.AbstractSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* This class provides a skeletal implementation of {@link Network}. It is recommended to extend
* this class rather than implement {@link Network} directly.
*
* The methods implemented in this class should not be overridden unless the subclass admits a
* more efficient implementation.
*
* @author James Sexton
* @param Node parameter type
* @param Edge parameter type
* @since 20.0
*/
@Beta
public abstract class AbstractNetwork implements Network {
@Override
public Graph asGraph() {
return new AbstractGraph() {
@Override
public Set nodes() {
return AbstractNetwork.this.nodes();
}
@Override
public Set> edges() {
if (allowsParallelEdges()) {
return super.edges(); // Defer to AbstractGraph implementation.
}
// Optimized implementation assumes no parallel edges (1:1 edge to EndpointPair mapping).
return new AbstractSet>() {
@Override
public Iterator> iterator() {
return Iterators.transform(
AbstractNetwork.this.edges().iterator(),
new Function>() {
@Override
public EndpointPair apply(E edge) {
return incidentNodes(edge);
}
});
}
@Override
public int size() {
return AbstractNetwork.this.edges().size();
}
// Mostly safe: We check contains(u) before calling successors(u), so we perform unsafe
// operations only in weird cases like checking for an EndpointPair in a
// Network.
@SuppressWarnings("unchecked")
@Override
public boolean contains(@Nullable Object obj) {
if (!(obj instanceof EndpointPair)) {
return false;
}
EndpointPair endpointPair = (EndpointPair) obj;
return isOrderingCompatible(endpointPair)
&& nodes().contains(endpointPair.nodeU())
&& successors((N) endpointPair.nodeU()).contains(endpointPair.nodeV());
}
};
}
@Override
public ElementOrder nodeOrder() {
return AbstractNetwork.this.nodeOrder();
}
@Override
public ElementOrder incidentEdgeOrder() {
// TODO(b/142723300): Return AbstractNetwork.this.incidentEdgeOrder() once Network has that
// method.
return ElementOrder.unordered();
}
@Override
public boolean isDirected() {
return AbstractNetwork.this.isDirected();
}
@Override
public boolean allowsSelfLoops() {
return AbstractNetwork.this.allowsSelfLoops();
}
@Override
public Set adjacentNodes(N node) {
return AbstractNetwork.this.adjacentNodes(node);
}
@Override
public Set predecessors(N node) {
return AbstractNetwork.this.predecessors(node);
}
@Override
public Set successors(N node) {
return AbstractNetwork.this.successors(node);
}
// DO NOT override the AbstractGraph *degree() implementations.
};
}
@Override
public int degree(N node) {
if (isDirected()) {
return IntMath.saturatedAdd(inEdges(node).size(), outEdges(node).size());
} else {
return IntMath.saturatedAdd(incidentEdges(node).size(), edgesConnecting(node, node).size());
}
}
@Override
public int inDegree(N node) {
return isDirected() ? inEdges(node).size() : degree(node);
}
@Override
public int outDegree(N node) {
return isDirected() ? outEdges(node).size() : degree(node);
}
@Override
public Set adjacentEdges(E edge) {
EndpointPair endpointPair = incidentNodes(edge); // Verifies that edge is in this network.
Set endpointPairIncidentEdges =
Sets.union(incidentEdges(endpointPair.nodeU()), incidentEdges(endpointPair.nodeV()));
return Sets.difference(endpointPairIncidentEdges, ImmutableSet.of(edge));
}
@Override
public Set edgesConnecting(N nodeU, N nodeV) {
Set outEdgesU = outEdges(nodeU);
Set inEdgesV = inEdges(nodeV);
return outEdgesU.size() <= inEdgesV.size()
? unmodifiableSet(Sets.filter(outEdgesU, connectedPredicate(nodeU, nodeV)))
: unmodifiableSet(Sets.filter(inEdgesV, connectedPredicate(nodeV, nodeU)));
}
@Override
public Set edgesConnecting(EndpointPair endpoints) {
validateEndpoints(endpoints);
return edgesConnecting(endpoints.nodeU(), endpoints.nodeV());
}
private Predicate connectedPredicate(final N nodePresent, final N nodeToCheck) {
return new Predicate() {
@Override
public boolean apply(E edge) {
return incidentNodes(edge).adjacentNode(nodePresent).equals(nodeToCheck);
}
};
}
@Override
public Optional edgeConnecting(N nodeU, N nodeV) {
return Optional.ofNullable(edgeConnectingOrNull(nodeU, nodeV));
}
@Override
public Optional edgeConnecting(EndpointPair endpoints) {
validateEndpoints(endpoints);
return edgeConnecting(endpoints.nodeU(), endpoints.nodeV());
}
@Override
public @Nullable E edgeConnectingOrNull(N nodeU, N nodeV) {
Set edgesConnecting = edgesConnecting(nodeU, nodeV);
switch (edgesConnecting.size()) {
case 0:
return null;
case 1:
return edgesConnecting.iterator().next();
default:
throw new IllegalArgumentException(String.format(MULTIPLE_EDGES_CONNECTING, nodeU, nodeV));
}
}
@Override
public @Nullable E edgeConnectingOrNull(EndpointPair endpoints) {
validateEndpoints(endpoints);
return edgeConnectingOrNull(endpoints.nodeU(), endpoints.nodeV());
}
@Override
public boolean hasEdgeConnecting(N nodeU, N nodeV) {
checkNotNull(nodeU);
checkNotNull(nodeV);
return nodes().contains(nodeU) && successors(nodeU).contains(nodeV);
}
@Override
public boolean hasEdgeConnecting(EndpointPair endpoints) {
checkNotNull(endpoints);
if (!isOrderingCompatible(endpoints)) {
return false;
}
return hasEdgeConnecting(endpoints.nodeU(), endpoints.nodeV());
}
/**
* Throws an IllegalArgumentException if the ordering of {@code endpoints} is not compatible with
* the directionality of this graph.
*/
protected final void validateEndpoints(EndpointPair endpoints) {
checkNotNull(endpoints);
checkArgument(isOrderingCompatible(endpoints), ENDPOINTS_MISMATCH);
}
protected final boolean isOrderingCompatible(EndpointPair endpoints) {
return endpoints.isOrdered() || !this.isDirected();
}
@Override
public final boolean equals(@Nullable Object obj) {
if (obj == this) {
return true;
}
if (!(obj instanceof Network)) {
return false;
}
Network other = (Network) obj;
return isDirected() == other.isDirected()
&& nodes().equals(other.nodes())
&& edgeIncidentNodesMap(this).equals(edgeIncidentNodesMap(other));
}
@Override
public final int hashCode() {
return edgeIncidentNodesMap(this).hashCode();
}
/** Returns a string representation of this network. */
@Override
public String toString() {
return "isDirected: "
+ isDirected()
+ ", allowsParallelEdges: "
+ allowsParallelEdges()
+ ", allowsSelfLoops: "
+ allowsSelfLoops()
+ ", nodes: "
+ nodes()
+ ", edges: "
+ edgeIncidentNodesMap(this);
}
private static Map> edgeIncidentNodesMap(final Network network) {
Function> edgeToIncidentNodesFn =
new Function>() {
@Override
public EndpointPair apply(E edge) {
return network.incidentNodes(edge);
}
};
return Maps.asMap(network.edges(), edgeToIncidentNodesFn);
}
}