// Do not edit this file.
// Modified for homework: break ties by v and w.  That way we get a
// uniquely defined MST for any input file, no matter how you compute it.

/*************************************************************************
 *  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 RuntimeException("Illegal endpoint");
    }

   /**
     * Compare edges by weight.
     */
    // NO: Break ties by the unordered pair of vertex ids.

    public int compareTo(Edge that) {
        // return Double.compare(weight, that.weight);
        if (weight < that.weight) return -1;
        if (weight > that.weight) return +1;
        /*
        // Break ties by {v,w} (an unordered pair!).
        // First try to break ties by the sum v+w.
        // So, if two edges of the same weight share an endpoint,
        // we break the tie by the other endpoint.
        int sumdiff = (v+w) - (that.v+that.w);
        // Compare by abs(v-w) instead.
        return Math.abs(v-w) - Math.abs(that.v-that.w);
        // If this returns zero, the edges are identical,
        // except possibly for swapping v and w.
        */
        return 0;
    }

    /**
     * Return a string representation of this edge.
     */
    public String toString() {
        return String.format("%d-%d %.5f", v, w, weight);
    }
}