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

/**
 *  The {@code Edge} 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);
	}
}