// Source code example for "A Practical Introduction
// to Data Structures and Algorithm Analysis"
// by Clifford A. Shaffer, Prentice Hall, 1998.
// Copyright 1998 by Clifford A. Shaffer

class Graphl implements Graph {          // Graph: Adjacency list
  private GraphList[] vertex;            // The vertex list
  private int numEdge;                   // Number of edges
  public int[] Mark;                     // The mark array

  public Graphl(int n) {                 // Constructor
    Mark = new int[n];
    vertex = new GraphList[n];
    for (int i=0; i<n; i++)
      vertex[i] = new GraphList();
    numEdge = 0;
  }

  public int n() { return Mark.length; } // Number of vertices

  public int e() { return numEdge; }     // Number of edges

  public Edge first(int v) { // Get the first edge for a vertex
    vertex[v].setFirst();
    if (vertex[v].currValue() == null) return null;
    return new Edgel(v, ((int[])vertex[v].currValue())[0],
                        vertex[v].currLink());
  }

  public boolean isEdge(Edge e) { // True if this is an edge
    if (e == null) return false;
    vertex[e.v1()].setCurr(((Edgel)e).theLink());
    if (!vertex[e.v1()].isInList()) return false;
    return ((int[])vertex[e.v1()].currValue())[0] == e.v2();
  }

  public int v1(Edge e) { return e.v1(); } // Where edge comes from

  public int v2(Edge e) { return e.v2(); } // Where edge goes to
  public boolean isEdge(int i, int j) { // True if this is an edge
    GraphList temp = vertex[i];
    for (temp.setFirst(); ((temp.currValue() != null) &&
           (((int[])temp.currValue())[0] < j)); temp.next());
    return (temp.currValue() != null) &&
            (((int[])temp.currValue())[0] == j);
  }

  public Edge next(Edge e) { // Get next edge for a vertex
    vertex[e.v1()].setCurr(((Edgel)e).theLink());
    vertex[e.v1()].next();
    if (vertex[e.v1()].currValue() == null) return null;
    return new Edgel(e.v1(), ((int[])vertex[e.v1()].currValue())[0],
                             vertex[e.v1()].currLink());
  }

  public void setEdge(int i, int j, int weight) { // Set edge weight
    Assert.notFalse(weight!=0, "Cannot set weight to 0");
    int[] currEdge = { j, weight };
    if (isEdge(i, j))           // Edge already exists in graph
      vertex[i].setValue(currEdge);
    else {                      // Add new edge to graph
      vertex[i].insert(currEdge);
      numEdge++;
    }
  }

  public void setEdge(Edge w, int weight) // Set edge weight
    { if (w != null) setEdge(w.v1(), w.v2(), weight); }

  public void delEdge(int i, int j)  // Delete edge
    { if (isEdge(i, j)) { vertex[i].remove(); numEdge--; } }

  public void delEdge(Edge w)        // Delete edge
    { if (w != null) delEdge(w.v1(), w.v2()); }

  public int weight(int i, int j) {  // Return weight of edge
    if (isEdge(i, j)) return ((int[])vertex[i].currValue())[1];
    else return Integer.MAX_VALUE;
  }

  public int weight(Edge e) {    // Return weight of edge
    if (isEdge(e)) return ((int[])vertex[e.v1()].currValue())[1];
    else return Integer.MAX_VALUE;
  }

  public void setMark(int v, int val) { Mark[v] = val; } // Set Mark

  public int getMark(int v) { return Mark[v]; }          // Get Mark
} // class Graphl