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package algs43;
import stdlib.*;
/* ***********************************************************************
 *  Compilation:  javac Edge.java
 *  Execution:    java Edge
 *
 *  Immutable weighted edge.
 *
 *************************************************************************/

/**
 *  The <tt>Edge</tt> class represents a weighted edge in an undirected graph.
 *  <p>
 *  For additional documentation, see <a href="http://algs4.cs.princeton.edu/43mst">Section 4.3</a> of
 *  <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
 */
public class Edge implements Comparable<Edge> {

  private final int v;
  private final int w;
  private final double weight;

  /**
   * Create an edge between v and w with given weight.
   */
  public Edge(int v, int w, double weight) {
    this.v = v;
    this.w = w;
    this.weight = weight;
  }

  /**
   * Return the weight of this edge.
   */
  public double weight() {
    return weight;
  }

  /**
   * Return either endpoint of this edge.
   */
  public int either() {
    return v;
  }

  /**
   * Return the endpoint of this edge that is different from the given vertex
   * (unless a self-loop).
   */
  public int other(int vertex) {
    if      (vertex == v) return w;
    else if (vertex == w) return v;
    else throw new Error("Illegal endpoint");
  }

  /**
   * Compare edges by weight.
   */
  public int compareTo(Edge that) {
    if      (this.weight() < that.weight()) return -1;
    else if (this.weight() > that.weight()) return +1;
    else                                    return  0;
  }


  /**
   * Return a string representation of this edge.
   */
  public String toString() {
    return String.format("%d--%d %.2f", v, w, weight);
  }


  /**
   * Test client.
   */
  public static void main(String[] args) {
    Edge e = new Edge(12, 23, 3.14);
    StdOut.println(e);
  }
}