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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.base.Preconditions.checkState;
import static com.google.common.graph.GraphConstants.SELF_LOOPS_NOT_ALLOWED;
import static com.google.common.graph.Graphs.checkNonNegative;
import static com.google.common.graph.Graphs.checkPositive;
import static java.util.Objects.requireNonNull;

import com.google.common.collect.ImmutableList;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import javax.annotation.CheckForNull;

/**
 * Standard implementation of {@link MutableValueGraph} that supports both directed and undirected
 * graphs. Instances of this class should be constructed with {@link ValueGraphBuilder}.
 *
 * 

Time complexities for mutation methods are all O(1) except for {@code removeNode(N node)}, * which is in O(d_node) where d_node is the degree of {@code node}. * * @author James Sexton * @author Joshua O'Madadhain * @author Omar Darwish * @param Node parameter type * @param Value parameter type */ @ElementTypesAreNonnullByDefault final class StandardMutableValueGraph extends StandardValueGraph implements MutableValueGraph { private final ElementOrder incidentEdgeOrder; /** Constructs a mutable graph with the properties specified in {@code builder}. */ StandardMutableValueGraph(AbstractGraphBuilder builder) { super(builder); incidentEdgeOrder = builder.incidentEdgeOrder.cast(); } @Override public ElementOrder incidentEdgeOrder() { return incidentEdgeOrder; } @Override @CanIgnoreReturnValue public boolean addNode(N node) { checkNotNull(node, "node"); if (containsNode(node)) { return false; } addNodeInternal(node); return true; } /** * Adds {@code node} to the graph and returns the associated {@link GraphConnections}. * * @throws IllegalStateException if {@code node} is already present */ @CanIgnoreReturnValue private GraphConnections addNodeInternal(N node) { GraphConnections connections = newConnections(); checkState(nodeConnections.put(node, connections) == null); return connections; } @Override @CanIgnoreReturnValue @CheckForNull public V putEdgeValue(N nodeU, N nodeV, V value) { checkNotNull(nodeU, "nodeU"); checkNotNull(nodeV, "nodeV"); checkNotNull(value, "value"); if (!allowsSelfLoops()) { checkArgument(!nodeU.equals(nodeV), SELF_LOOPS_NOT_ALLOWED, nodeU); } GraphConnections connectionsU = nodeConnections.get(nodeU); if (connectionsU == null) { connectionsU = addNodeInternal(nodeU); } V previousValue = connectionsU.addSuccessor(nodeV, value); GraphConnections connectionsV = nodeConnections.get(nodeV); if (connectionsV == null) { connectionsV = addNodeInternal(nodeV); } connectionsV.addPredecessor(nodeU, value); if (previousValue == null) { checkPositive(++edgeCount); } return previousValue; } @Override @CanIgnoreReturnValue @CheckForNull public V putEdgeValue(EndpointPair endpoints, V value) { validateEndpoints(endpoints); return putEdgeValue(endpoints.nodeU(), endpoints.nodeV(), value); } @Override @CanIgnoreReturnValue public boolean removeNode(N node) { checkNotNull(node, "node"); GraphConnections connections = nodeConnections.get(node); if (connections == null) { return false; } if (allowsSelfLoops()) { // Remove self-loop (if any) first, so we don't get CME while removing incident edges. if (connections.removeSuccessor(node) != null) { connections.removePredecessor(node); --edgeCount; } } for (N successor : ImmutableList.copyOf(connections.successors())) { // requireNonNull is safe because the node is a successor. requireNonNull(nodeConnections.getWithoutCaching(successor)).removePredecessor(node); requireNonNull(connections.removeSuccessor(successor)); --edgeCount; } if (isDirected()) { // In undirected graphs, the successor and predecessor sets are equal. // Since views are returned, we need to copy the predecessors that will be removed. // Thus we avoid modifying the underlying view while iterating over it. for (N predecessor : ImmutableList.copyOf(connections.predecessors())) { // requireNonNull is safe because the node is a predecessor. checkState( requireNonNull(nodeConnections.getWithoutCaching(predecessor)).removeSuccessor(node) != null); connections.removePredecessor(predecessor); --edgeCount; } } nodeConnections.remove(node); checkNonNegative(edgeCount); return true; } @Override @CanIgnoreReturnValue @CheckForNull public V removeEdge(N nodeU, N nodeV) { checkNotNull(nodeU, "nodeU"); checkNotNull(nodeV, "nodeV"); GraphConnections connectionsU = nodeConnections.get(nodeU); GraphConnections connectionsV = nodeConnections.get(nodeV); if (connectionsU == null || connectionsV == null) { return null; } V previousValue = connectionsU.removeSuccessor(nodeV); if (previousValue != null) { connectionsV.removePredecessor(nodeU); checkNonNegative(--edgeCount); } return previousValue; } @Override @CanIgnoreReturnValue @CheckForNull public V removeEdge(EndpointPair endpoints) { validateEndpoints(endpoints); return removeEdge(endpoints.nodeU(), endpoints.nodeV()); } private GraphConnections newConnections() { return isDirected() ? DirectedGraphConnections.of(incidentEdgeOrder) : UndirectedGraphConnections.of(incidentEdgeOrder); } }





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