EdgeWeightedDigraph.java
9.86 KB
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
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
/******************************************************************************
* Compilation: javac EdgeWeightedDigraph.java
* Execution: java EdgeWeightedDigraph digraph.txt
* Dependencies: Bag.java DirectedEdge.java
* Data files: http://algs4.cs.princeton.edu/44st/tinyEWD.txt
* http://algs4.cs.princeton.edu/44st/mediumEWD.txt
* http://algs4.cs.princeton.edu/44st/largeEWD.txt
*
* An edge-weighted digraph, implemented using adjacency lists.
*
******************************************************************************/
package edu.princeton.cs.algs4;
/**
* The {@code EdgeWeightedDigraph} class represents a edge-weighted
* digraph of vertices named 0 through <em>V</em> - 1, where each
* directed edge is of type {@link DirectedEdge} and has a real-valued weight.
* It supports the following two primary operations: add a directed edge
* to the digraph and iterate over all of edges incident from a given vertex.
* It also provides
* methods for returning the number of vertices <em>V</em> and the number
* of edges <em>E</em>. Parallel edges and self-loops are permitted.
* <p>
* This implementation uses an adjacency-lists representation, which
* is a vertex-indexed array of @link{Bag} objects.
* All operations take constant time (in the worst case) except
* iterating over the edges incident from a given vertex, which takes
* time proportional to the number of such edges.
* <p>
* For additional documentation,
* see <a href="http://algs4.cs.princeton.edu/44sp">Section 4.4</a> of
* <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class EdgeWeightedDigraph {
private static final String NEWLINE = System.getProperty("line.separator");
private final int V; // number of vertices in this digraph
private int E; // number of edges in this digraph
private Bag<DirectedEdge>[] adj; // adj[v] = adjacency list for vertex v
private int[] indegree; // indegree[v] = indegree of vertex v
/**
* Initializes an empty edge-weighted digraph with {@code V} vertices and 0 edges.
*
* @param V the number of vertices
* @throws IllegalArgumentException if {@code V < 0}
*/
public EdgeWeightedDigraph(int V) {
if (V < 0) throw new IllegalArgumentException("Number of vertices in a Digraph must be nonnegative");
this.V = V;
this.E = 0;
this.indegree = new int[V];
adj = (Bag<DirectedEdge>[]) new Bag[V];
for (int v = 0; v < V; v++)
adj[v] = new Bag<DirectedEdge>();
}
/**
* Initializes a random edge-weighted digraph with {@code V} vertices and <em>E</em> edges.
*
* @param V the number of vertices
* @param E the number of edges
* @throws IllegalArgumentException if {@code V < 0}
* @throws IllegalArgumentException if {@code E < 0}
*/
public EdgeWeightedDigraph(int V, int E) {
this(V);
if (E < 0) throw new IllegalArgumentException("Number of edges in a Digraph must be nonnegative");
for (int i = 0; i < E; i++) {
int v = StdRandom.uniform(V);
int w = StdRandom.uniform(V);
double weight = 0.01 * StdRandom.uniform(100);
DirectedEdge e = new DirectedEdge(v, w, weight);
addEdge(e);
}
}
/**
* Initializes an edge-weighted digraph from the specified input stream.
* The format is the number of vertices <em>V</em>,
* followed by the number of edges <em>E</em>,
* followed by <em>E</em> pairs of vertices and edge weights,
* with each entry separated by whitespace.
*
* @param in the input stream
* @throws IllegalArgumentException if the endpoints of any edge are not in prescribed range
* @throws IllegalArgumentException if the number of vertices or edges is negative
*/
public EdgeWeightedDigraph(In in) {
this(in.readInt());
int E = in.readInt();
if (E < 0) throw new IllegalArgumentException("Number of edges must be nonnegative");
for (int i = 0; i < E; i++) {
int v = in.readInt();
int w = in.readInt();
validateVertex(v);
validateVertex(w);
double weight = in.readDouble();
addEdge(new DirectedEdge(v, w, weight));
}
}
/**
* Initializes a new edge-weighted digraph that is a deep copy of {@code G}.
*
* @param G the edge-weighted digraph to copy
*/
public EdgeWeightedDigraph(EdgeWeightedDigraph G) {
this(G.V());
this.E = G.E();
for (int v = 0; v < G.V(); v++)
this.indegree[v] = G.indegree(v);
for (int v = 0; v < G.V(); v++) {
// reverse so that adjacency list is in same order as original
Stack<DirectedEdge> reverse = new Stack<DirectedEdge>();
for (DirectedEdge e : G.adj[v]) {
reverse.push(e);
}
for (DirectedEdge e : reverse) {
adj[v].add(e);
}
}
}
/**
* Returns the number of vertices in this edge-weighted digraph.
*
* @return the number of vertices in this edge-weighted digraph
*/
public int V() {
return V;
}
/**
* Returns the number of edges in this edge-weighted digraph.
*
* @return the number of edges in this edge-weighted digraph
*/
public int E() {
return E;
}
// throw an IllegalArgumentException unless {@code 0 <= v < V}
private void validateVertex(int v) {
if (v < 0 || v >= V)
throw new IllegalArgumentException("vertex " + v + " is not between 0 and " + (V-1));
}
/**
* Adds the directed edge {@code e} to this edge-weighted digraph.
*
* @param e the edge
* @throws IllegalArgumentException unless endpoints of edge are between {@code 0}
* and {@code V-1}
*/
public void addEdge(DirectedEdge e) {
int v = e.from();
int w = e.to();
validateVertex(v);
validateVertex(w);
adj[v].add(e);
indegree[w]++;
E++;
}
/**
* Returns the directed edges incident from vertex {@code v}.
*
* @param v the vertex
* @return the directed edges incident from vertex {@code v} as an Iterable
* @throws IllegalArgumentException unless {@code 0 <= v < V}
*/
public Iterable<DirectedEdge> adj(int v) {
validateVertex(v);
return adj[v];
}
/**
* Returns the number of directed edges incident from vertex {@code v}.
* This is known as the <em>outdegree</em> of vertex {@code v}.
*
* @param v the vertex
* @return the outdegree of vertex {@code v}
* @throws IllegalArgumentException unless {@code 0 <= v < V}
*/
public int outdegree(int v) {
validateVertex(v);
return adj[v].size();
}
/**
* Returns the number of directed edges incident to vertex {@code v}.
* This is known as the <em>indegree</em> of vertex {@code v}.
*
* @param v the vertex
* @return the indegree of vertex {@code v}
* @throws IllegalArgumentException unless {@code 0 <= v < V}
*/
public int indegree(int v) {
validateVertex(v);
return indegree[v];
}
/**
* Returns all directed edges in this edge-weighted digraph.
* To iterate over the edges in this edge-weighted digraph, use foreach notation:
* {@code for (DirectedEdge e : G.edges())}.
*
* @return all edges in this edge-weighted digraph, as an iterable
*/
public Iterable<DirectedEdge> edges() {
Bag<DirectedEdge> list = new Bag<DirectedEdge>();
for (int v = 0; v < V; v++) {
for (DirectedEdge e : adj(v)) {
list.add(e);
}
}
return list;
}
/**
* Returns a string representation of this edge-weighted digraph.
*
* @return the number of vertices <em>V</em>, followed by the number of edges <em>E</em>,
* followed by the <em>V</em> adjacency lists of edges
*/
public String toString() {
StringBuilder s = new StringBuilder();
s.append(V + " " + E + NEWLINE);
for (int v = 0; v < V; v++) {
s.append(v + ": ");
for (DirectedEdge e : adj[v]) {
s.append(e + " ");
}
s.append(NEWLINE);
}
return s.toString();
}
/**
* Unit tests the {@code EdgeWeightedDigraph} data type.
*
* @param args the command-line arguments
*/
public static void main(String[] args) {
In in = new In(args[0]);
EdgeWeightedDigraph G = new EdgeWeightedDigraph(in);
StdOut.println(G);
}
}
/******************************************************************************
* Copyright 2002-2016, Robert Sedgewick and Kevin Wayne.
*
* This file is part of algs4.jar, which accompanies the textbook
*
* Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne,
* Addison-Wesley Professional, 2011, ISBN 0-321-57351-X.
* http://algs4.cs.princeton.edu
*
*
* algs4.jar is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* algs4.jar is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with algs4.jar. If not, see http://www.gnu.org/licenses.
******************************************************************************/