content: /*************************************************************************
   *  Compilation:  javac EdgeWeightedGraph.java
   *  Execution:    java EdgeWeightedGraph filename.txt
   *  Dependencies: Bag.java Edge.java In.java StdOut.java
   *  Data files:   http://algs4.cs.princeton.edu/43mst/tinyEWG.txt
   *
   *  An edge-weighted undirected graph, implemented using adjacency lists.
   *  Parallel edges and self-loops are permitted.
   *
   *  % java EdgeWeightedGraph tinyEWG.txt 
   *  8 16
   *  0: 6-0 0.58000  0-2 0.26000  0-4 0.38000  0-7 0.16000  
   *  1: 1-3 0.29000  1-2 0.36000  1-7 0.19000  1-5 0.32000  
   *  2: 6-2 0.40000  2-7 0.34000  1-2 0.36000  0-2 0.26000  2-3 0.17000  
   *  3: 3-6 0.52000  1-3 0.29000  2-3 0.17000  
   *  4: 6-4 0.93000  0-4 0.38000  4-7 0.37000  4-5 0.35000  
   *  5: 1-5 0.32000  5-7 0.28000  4-5 0.35000  
   *  6: 6-4 0.93000  6-0 0.58000  3-6 0.52000  6-2 0.40000
   *  7: 2-7 0.34000  1-7 0.19000  0-7 0.16000  5-7 0.28000  4-7 0.37000
   *
   *************************************************************************/
  
  /**
   *  The <tt>EdgeWeightedGraph</tt> class represents an undirected graph of vertices
   *  named 0 through V-1, where each edge has a real-valued weight.
   *  It supports the following operations: add an edge to the graph,
   *  in the graph, iterate over all of the neighbors incident to a vertex.
   *  Parallel edges and self-loops are permitted.
   *  <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 EdgeWeightedGraph {
      private final int V;
      private int E;
      private Bag<Edge>[] adj;
      
     /**
       * Create an empty edge-weighted graph with V vertices.
       */
      public EdgeWeightedGraph(int V) {
          if (V < 0) throw new RuntimeException("Number of vertices must be nonnegative");
          this.V = V;
          this.E = 0;
          adj = (Bag<Edge>[]) new Bag[V];
          for (int v = 0; v < V; v++) {
              adj[v] = new Bag<Edge>();
          }
      }
  
     /**
       * Create a random edge-weighted graph with V vertices and E edges.
       * The expected running time is proportional to V + E.
       */
      public EdgeWeightedGraph(int V, int E) {
          this(V);
          if (E < 0) throw new RuntimeException("Number of edges must be nonnegative");
          for (int i = 0; i < E; i++) {
              int v = (int) (Math.random() * V);
              int w = (int) (Math.random() * V);
              double weight = Math.round(100 * Math.random()) / 100.0;
              Edge e = new Edge(v, w, weight);
              addEdge(e);
          }
      }
  
     /**
       * Create a weighted graph from input stream.
       */
      public EdgeWeightedGraph(In in) {
          this(in.readInt());
          int E = in.readInt();
          for (int i = 0; i < E; i++) {
              int v = in.readInt();
              int w = in.readInt();
              double weight = in.readDouble();
              Edge e = new Edge(v, w, weight);
              addEdge(e);
          }
      }
  
     /**
       * Copy constructor.
       */
      public EdgeWeightedGraph(EdgeWeightedGraph G) {
          this(G.V());
          this.E = G.E();
          for (int v = 0; v < G.V(); v++) {
              // reverse so that adjacency list is in same order as original
              Stack<Edge> reverse = new Stack<Edge>();
              for (Edge e : G.adj[v]) {
                  reverse.push(e);
              }
              for (Edge e : reverse) {
                  adj[v].add(e);
              }
          }
      }
  
     /**
       * Return the number of vertices in this graph.
       */
      public int V() {
          return V;
      }
  
     /**
       * Return the number of edges in this graph.
       */
      public int E() {
          return E;
      }
  
  
     /**
       * Add the edge e to this graph.
       */
      public void addEdge(Edge e) {
          int v = e.either();
          int w = e.other(v);
          adj[v].add(e);
          adj[w].add(e);
          E++;
      }
  
  
     /**
       * Return the edges incident to vertex v as an Iterable.
       * To iterate over the edges incident to vertex v, use foreach notation:
       * <tt>for (Edge e : graph.adj(v))</tt>.
       */
      public Iterable<Edge> adj(int v) {
          return adj[v];
      }
  
     /**
       * Return all edges in this graph as an Iterable.
       * To iterate over the edges, use foreach notation:
       * <tt>for (Edge e : graph.edges())</tt>.
       */
      public Iterable<Edge> edges() {
          Bag<Edge> list = new Bag<Edge>();
          for (int v = 0; v < V; v++) {
              int selfLoops = 0;
              for (Edge e : adj(v)) {
                  if (e.other(v) > v) {
                      list.add(e);
                  }
                  // only add one copy of each self loop
                  else if (e.other(v) == v) {
                      if (selfLoops % 2 == 0) list.add(e);
                      selfLoops++;
                  }
              }
          }
          return list;
      }
  
  
  
     /**
       * Return a string representation of this graph.
       */
      public String toString() {
          String NEWLINE = System.getProperty("line.separator");
          StringBuilder s = new StringBuilder();
          s.append(V + " " + E + NEWLINE);
          for (int v = 0; v < V; v++) {
              s.append(v + ": ");
              for (Edge e : adj[v]) {
                  s.append(e + "  ");
              }
              s.append(NEWLINE);
          }
          return s.toString();
      }
  
     /**
       * Test client.
       */
      public static void main(String[] args) {
          In in = new In(args[0]);
          EdgeWeightedGraph G = new EdgeWeightedGraph(in);
          StdOut.println(G);
      }
  
  }
  