edu.princeton.cs.algs4.SymbolDigraph Maven / Gradle / Ivy
Show all versions of algorithm Show documentation
/******************************************************************************
* Compilation: javac SymbolDigraph.java
* Execution: java SymbolDigraph
* Dependencies: ST.java Digraph.java In.java
* Data files: https://algs4.cs.princeton.edu/42digraph/routes.txt
*
* % java SymbolDigraph routes.txt " "
* JFK
* MCO
* ATL
* ORD
* ATL
* HOU
* MCO
* LAX
*
******************************************************************************/
package edu.princeton.cs.algs4;
/**
* The {@code SymbolDigraph} class represents a digraph, where the
* vertex names are arbitrary strings.
* By providing mappings between string vertex names and integers,
* it serves as a wrapper around the
* {@link Digraph} data type, which assumes the vertex names are integers
* between 0 and V - 1.
* It also supports initializing a symbol digraph from a file.
*
* This implementation uses an {@link ST} to map from strings to integers,
* an array to map from integers to strings, and a {@link Digraph} to store
* the underlying graph.
* The indexOf and contains operations take time
* proportional to log V, where V is the number of vertices.
* The nameOf operation takes constant time.
*
* For additional documentation, see Section 4.2 of
* Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class SymbolDigraph {
private ST st; // string -> index
private String[] keys; // index -> string
private Digraph graph; // the underlying digraph
/**
* Initializes a digraph from a file using the specified delimiter.
* Each line in the file contains
* the name of a vertex, followed by a list of the names
* of the vertices adjacent to that vertex, separated by the delimiter.
* @param filename the name of the file
* @param delimiter the delimiter between fields
*/
public SymbolDigraph(String filename, String delimiter) {
st = new ST();
// First pass builds the index by reading strings to associate
// distinct strings with an index
In in = new In(filename);
while (in.hasNextLine()) {
String[] a = in.readLine().split(delimiter);
for (int i = 0; i < a.length; i++) {
if (!st.contains(a[i]))
st.put(a[i], st.size());
}
}
// inverted index to get string keys in an array
keys = new String[st.size()];
for (String name : st.keys()) {
keys[st.get(name)] = name;
}
// second pass builds the digraph by connecting first vertex on each
// line to all others
graph = new Digraph(st.size());
in = new In(filename);
while (in.hasNextLine()) {
String[] a = in.readLine().split(delimiter);
int v = st.get(a[0]);
for (int i = 1; i < a.length; i++) {
int w = st.get(a[i]);
graph.addEdge(v, w);
}
}
}
/**
* Does the digraph contain the vertex named {@code s}?
* @param s the name of a vertex
* @return {@code true} if {@code s} is the name of a vertex, and {@code false} otherwise
*/
public boolean contains(String s) {
return st.contains(s);
}
/**
* Returns the integer associated with the vertex named {@code s}.
* @param s the name of a vertex
* @return the integer (between 0 and V - 1) associated with the vertex named {@code s}
* @deprecated Replaced by {@link #indexOf(String)}.
*/
@Deprecated
public int index(String s) {
return st.get(s);
}
/**
* Returns the integer associated with the vertex named {@code s}.
* @param s the name of a vertex
* @return the integer (between 0 and V - 1) associated with the vertex named {@code s}
*/
public int indexOf(String s) {
return st.get(s);
}
/**
* Returns the name of the vertex associated with the integer {@code v}.
* @param v the integer corresponding to a vertex (between 0 and V - 1)
* @return the name of the vertex associated with the integer {@code v}
* @throws IllegalArgumentException unless {@code 0 <= v < V}
* @deprecated Replaced by {@link #nameOf(int)}.
*/
@Deprecated
public String name(int v) {
validateVertex(v);
return keys[v];
}
/**
* Returns the name of the vertex associated with the integer {@code v}.
* @param v the integer corresponding to a vertex (between 0 and V - 1)
* @return the name of the vertex associated with the integer {@code v}
* @throws IllegalArgumentException unless {@code 0 <= v < V}
*/
public String nameOf(int v) {
validateVertex(v);
return keys[v];
}
/**
* Returns the digraph assoicated with the symbol graph. It is the client's responsibility
* not to mutate the digraph.
*
* @return the digraph associated with the symbol digraph
* @deprecated Replaced by {@link #digraph()}.
*/
@Deprecated
public Digraph G() {
return graph;
}
/**
* Returns the digraph assoicated with the symbol graph. It is the client's responsibility
* not to mutate the digraph.
*
* @return the digraph associated with the symbol digraph
*/
public Digraph digraph() {
return graph;
}
// throw an IllegalArgumentException unless {@code 0 <= v < V}
private void validateVertex(int v) {
int V = graph.V();
if (v < 0 || v >= V)
throw new IllegalArgumentException("vertex " + v + " is not between 0 and " + (V-1));
}
/**
* Unit tests the {@code SymbolDigraph} data type.
*
* @param args the command-line arguments
*/
public static void main(String[] args) {
String filename = args[0];
String delimiter = args[1];
SymbolDigraph sg = new SymbolDigraph(filename, delimiter);
Digraph graph = sg.digraph();
while (!StdIn.isEmpty()) {
String t = StdIn.readLine();
for (int v : graph.adj(sg.index(t))) {
StdOut.println(" " + sg.name(v));
}
}
}
}
/******************************************************************************
* Copyright 2002-2018, 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.
******************************************************************************/