/******************************************************************************
* Compilation: javac Edge.java
* Execution: java Edge
* Dependencies: StdOut.java
*
* Immutable weighted edge.
*
******************************************************************************/
package edu.princeton.cs.algs4;
/**
* The {@code Edge} class represents a weighted edge in an
* {@link EdgeWeightedGraph}. Each edge consists of two integers
* (naming the two vertices) and a real-value weight. The data type
* provides methods for accessing the two endpoints of the edge and
* the weight. The natural order for this data type is by
* ascending order of weight.
*
* For additional documentation, see Section 4.3 of
* Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class Edge implements Comparable {
private final int v;
private final int w;
private final double weight;
/**
* Initializes an edge between vertices {@code v} and {@code w} of
* the given {@code weight}.
*
* @param v one vertex
* @param w the other vertex
* @param weight the weight of this edge
* @throws IllegalArgumentException if either {@code v} or {@code w}
* is a negative integer
* @throws IllegalArgumentException if {@code weight} is {@code NaN}
*/
public Edge(int v, int w, double weight) {
if (v < 0) throw new IllegalArgumentException("vertex index must be a non-negative integer");
if (w < 0) throw new IllegalArgumentException("vertex index must be a non-negative integer");
if (Double.isNaN(weight)) throw new IllegalArgumentException("Weight is NaN");
this.v = v;
this.w = w;
this.weight = weight;
}
/**
* Returns the weight of this edge.
*
* @return the weight of this edge
*/
public double weight() {
return weight;
}
/**
* Returns either endpoint of this edge.
*
* @return either endpoint of this edge
*/
public int either() {
return v;
}
/**
* Returns the endpoint of this edge that is different from the given vertex.
*
* @param vertex one endpoint of this edge
* @return the other endpoint of this edge
* @throws IllegalArgumentException if the vertex is not one of the
* endpoints of this edge
*/
public int other(int vertex) {
if (vertex == v) return w;
else if (vertex == w) return v;
else throw new IllegalArgumentException("Illegal endpoint");
}
/**
* Compares two edges by weight.
* Note that {@code compareTo()} is not consistent with {@code equals()},
* which uses the reference equality implementation inherited from {@code Object}.
*
* @param that the other edge
* @return a negative integer, zero, or positive integer depending on whether
* the weight of this is less than, equal to, or greater than the
* argument edge
*/
@Override
public int compareTo(Edge that) {
return Double.compare(this.weight, that.weight);
}
/**
* Returns a string representation of this edge.
*
* @return a string representation of this edge
*/
public String toString() {
return String.format("%d-%d %.5f", v, w, weight);
}
/**
* Unit tests the {@code Edge} data type.
*
* @param args the command-line arguments
*/
public static void main(String[] args) {
Edge e = new Edge(12, 34, 5.67);
StdOut.println(e);
}
}
/******************************************************************************
* Copyright 2002-2022, 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.
******************************************************************************/