112 lines
3.6 KiB
Java
112 lines
3.6 KiB
Java
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import edu.princeton.cs.introcs.StdOut;
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/*************************************************************************
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* Compilation: javac Edge.java
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* Execution: java Edge
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*
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* Immutable weighted edge.
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*
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*************************************************************************/
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/**
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* The Edge class represents a weighted edge in an
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* {@link EdgeWeightedGraph}. Each edge consists of two integers
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* (naming the two vertices) and a real-value weight. The data type
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* provides methods for accessing the two endpoints of the edge and
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* the weight. The natural order for this data type is by
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* ascending order of weight.
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*
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* For additional documentation, see <a href="http://algs4.cs.princeton.edu/43mst">Section 4.3</a> of
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* Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.
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*
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* @author Robert Sedgewick
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* @author Kevin Wayne
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*/
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public class Edge implements Comparable<Edge> {
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private final int v;
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private final int w;
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private final double weight;
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/**
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* Initializes an edge between vertices v/tt> and w of
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* the given weight .
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* param v one vertex
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* param w the other vertex
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* param weight the weight of the edge
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* @throws IndexOutOfBoundsException if either v or w
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* is a negative integer
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* @throws IllegalArgumentException if weight is NaN
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*/
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public Edge(int v, int w, double weight) {
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if (v < 0) throw new IndexOutOfBoundsException("Vertex name must be a nonnegative integer");
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if (w < 0) throw new IndexOutOfBoundsException("Vertex name must be a nonnegative integer");
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if (Double.isNaN(weight)) throw new IllegalArgumentException("Weight is NaN");
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this.v = v;
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this.w = w;
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this.weight = weight;
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}
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/**
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* Returns the weight of the edge.
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* @return the weight of the edge
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*/
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public double weight() {
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return weight;
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}
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/**
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* Returns either endpoint of the edge.
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* @return either endpoint of the edge
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*/
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public int either() {
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return v;
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}
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/**
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* Returns the endpoint of the edge that is different from the given vertex
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* (unless the edge represents a self-loop in which case it returns the same vertex).
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* @param vertex one endpoint of the edge
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* @return the endpoint of the edge that is different from the given vertex
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* (unless the edge represents a self-loop in which case it returns the same vertex)
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* @throws java.lang.IllegalArgumentException if the vertex is not one of the endpoints
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* of the edge
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*/
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public int other(int vertex) {
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if (vertex == v) return w;
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else if (vertex == w) return v;
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else throw new IllegalArgumentException("Illegal endpoint");
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}
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/**
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* Compares two edges by weight.
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* @param that the other edge
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* @return a negative integer, zero, or positive integer depending on whether
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* this edge is less than, equal to, or greater than that edge
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*/
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public int compareTo(Edge that) {
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if (this.weight() < that.weight()) return -1;
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else if (this.weight() > that.weight()) return +1;
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else return 0;
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}
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/**
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* Returns a string representation of the edge.
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* @return a string representation of the edge
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*/
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@Override
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public String toString() {
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return String.format("%d-%d %.5f", v, w, weight);
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}
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/**
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* Unit tests the Edge data type.
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*/
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public static void main(String[] args) {
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Edge e = new Edge(12, 23, 3.14);
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StdOut.println(e);
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}
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}
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