1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
|
/*
* 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.DEFAULT_EDGE_COUNT;
import static com.google.common.graph.GraphConstants.DEFAULT_NODE_COUNT;
import static com.google.common.graph.GraphConstants.EDGE_NOT_IN_GRAPH;
import static com.google.common.graph.GraphConstants.NODE_NOT_IN_GRAPH;
import com.google.common.collect.ImmutableSet;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import org.checkerframework.checker.nullness.compatqual.NullableDecl;
/**
* Standard implementation of {@link Network} that supports the options supplied by {@link
* NetworkBuilder}.
*
* <p>This class maintains a map of nodes to {@link NetworkConnections}. This class also maintains a
* map of edges to reference nodes. The reference node is defined to be the edge's source node on
* directed graphs, and an arbitrary endpoint of the edge on undirected graphs.
*
* <p>Collection-returning accessors return unmodifiable views: the view returned will reflect
* changes to the graph (if the graph is mutable) but may not be modified by the user.
*
* <p>The time complexity of all collection-returning accessors is O(1), since views are returned.
*
* @author James Sexton
* @author Joshua O'Madadhain
* @author Omar Darwish
* @param <N> Node parameter type
* @param <E> Edge parameter type
*/
class StandardNetwork<N, E> extends AbstractNetwork<N, E> {
private final boolean isDirected;
private final boolean allowsParallelEdges;
private final boolean allowsSelfLoops;
private final ElementOrder<N> nodeOrder;
private final ElementOrder<E> edgeOrder;
protected final MapIteratorCache<N, NetworkConnections<N, E>> nodeConnections;
// We could make this a Map<E, EndpointPair<N>>. It would make incidentNodes(edge) slightly
// faster, but also make Networks consume 5 to 20+% (increasing with average degree) more memory.
protected final MapIteratorCache<E, N> edgeToReferenceNode; // referenceNode == source if directed
/** Constructs a graph with the properties specified in {@code builder}. */
StandardNetwork(NetworkBuilder<? super N, ? super E> builder) {
this(
builder,
builder.nodeOrder.<N, NetworkConnections<N, E>>createMap(
builder.expectedNodeCount.or(DEFAULT_NODE_COUNT)),
builder.edgeOrder.<E, N>createMap(builder.expectedEdgeCount.or(DEFAULT_EDGE_COUNT)));
}
/**
* Constructs a graph with the properties specified in {@code builder}, initialized with the given
* node and edge maps.
*/
StandardNetwork(
NetworkBuilder<? super N, ? super E> builder,
Map<N, NetworkConnections<N, E>> nodeConnections,
Map<E, N> edgeToReferenceNode) {
this.isDirected = builder.directed;
this.allowsParallelEdges = builder.allowsParallelEdges;
this.allowsSelfLoops = builder.allowsSelfLoops;
this.nodeOrder = builder.nodeOrder.cast();
this.edgeOrder = builder.edgeOrder.cast();
// Prefer the heavier "MapRetrievalCache" for nodes if lookup is expensive. This optimizes
// methods that access the same node(s) repeatedly, such as Graphs.removeEdgesConnecting().
this.nodeConnections =
(nodeConnections instanceof TreeMap)
? new MapRetrievalCache<N, NetworkConnections<N, E>>(nodeConnections)
: new MapIteratorCache<N, NetworkConnections<N, E>>(nodeConnections);
this.edgeToReferenceNode = new MapIteratorCache<>(edgeToReferenceNode);
}
@Override
public Set<N> nodes() {
return nodeConnections.unmodifiableKeySet();
}
@Override
public Set<E> edges() {
return edgeToReferenceNode.unmodifiableKeySet();
}
@Override
public boolean isDirected() {
return isDirected;
}
@Override
public boolean allowsParallelEdges() {
return allowsParallelEdges;
}
@Override
public boolean allowsSelfLoops() {
return allowsSelfLoops;
}
@Override
public ElementOrder<N> nodeOrder() {
return nodeOrder;
}
@Override
public ElementOrder<E> edgeOrder() {
return edgeOrder;
}
@Override
public Set<E> incidentEdges(N node) {
return checkedConnections(node).incidentEdges();
}
@Override
public EndpointPair<N> incidentNodes(E edge) {
N nodeU = checkedReferenceNode(edge);
N nodeV = nodeConnections.get(nodeU).adjacentNode(edge);
return EndpointPair.of(this, nodeU, nodeV);
}
@Override
public Set<N> adjacentNodes(N node) {
return checkedConnections(node).adjacentNodes();
}
@Override
public Set<E> edgesConnecting(N nodeU, N nodeV) {
NetworkConnections<N, E> connectionsU = checkedConnections(nodeU);
if (!allowsSelfLoops && nodeU == nodeV) { // just an optimization, only check reference equality
return ImmutableSet.of();
}
checkArgument(containsNode(nodeV), NODE_NOT_IN_GRAPH, nodeV);
return connectionsU.edgesConnecting(nodeV);
}
@Override
public Set<E> inEdges(N node) {
return checkedConnections(node).inEdges();
}
@Override
public Set<E> outEdges(N node) {
return checkedConnections(node).outEdges();
}
@Override
public Set<N> predecessors(N node) {
return checkedConnections(node).predecessors();
}
@Override
public Set<N> successors(N node) {
return checkedConnections(node).successors();
}
protected final NetworkConnections<N, E> checkedConnections(N node) {
NetworkConnections<N, E> connections = nodeConnections.get(node);
if (connections == null) {
checkNotNull(node);
throw new IllegalArgumentException(String.format(NODE_NOT_IN_GRAPH, node));
}
return connections;
}
protected final N checkedReferenceNode(E edge) {
N referenceNode = edgeToReferenceNode.get(edge);
if (referenceNode == null) {
checkNotNull(edge);
throw new IllegalArgumentException(String.format(EDGE_NOT_IN_GRAPH, edge));
}
return referenceNode;
}
protected final boolean containsNode(@NullableDecl N node) {
return nodeConnections.containsKey(node);
}
protected final boolean containsEdge(@NullableDecl E edge) {
return edgeToReferenceNode.containsKey(edge);
}
}
|
