// 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 Graphm implements Graph { // Graph: Adjacency matrix
  private int[][] matrix;                // The edge matrix
  private int numEdge;                   // Number of edges
  public int[] Mark;                     // The mark array

  public Graphm(int n) {                 // Constructor
    Mark = new int[n];
    matrix = new int[n][n];
    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
    for (int i=0; i<Mark.length; i++)
      if (matrix[v][i] != 0)
        return new Edgem(v, i);
    return null;  // No edge for this vertex
  }

  public Edge next(Edge w) { // Get next edge for a vertex
    if (w == null) return null;
    for (int i=w.v2()+1; i<Mark.length; i++)
      if (matrix[w.v1()][i] != 0)
        return new Edgem(w.v1(), i);
    return null;  // No next edge;
  }

  public boolean isEdge(Edge w) { // True if this is an edge
    if (w == null) return false;
    else return matrix[w.v1()][w.v2()] != 0;
  }

  public boolean isEdge(int i, int j) // True if this is an edge
    { return matrix[i][j] != 0; }
  public int v1(Edge w) { return w.v1(); } // Where edge comes from

  public int v2(Edge w) { return w.v2(); } // Where edge goes to

  public void setEdge(int i, int j, int wt) { // Set edge weight
    Assert.notFalse(wt!=0, "Cannot set weight to 0");
    matrix[i][j] = wt;
    numEdge++;
  }

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

  public void delEdge(Edge w) {       // Delete edge w
    if (w != null)
      if (matrix[w.v1()][w.v2()] != 0) {
        matrix[w.v1()][w.v2()] = 0;  
        numEdge--;
      }
  }

  public void delEdge(int i, int j) { // Delete edge (i, j)
    if (matrix[i][j] != 0) {
      matrix[i][j] = 0;
      numEdge--;
    }
  }

  public int weight(int i, int j) {  // Return weight of edge
    if (matrix[i][j] == 0) return Integer.MAX_VALUE;
    else return matrix[i][j];
  }

  public int weight(Edge w) {        // Return weight of edge
    Assert.notNull(w, "Can't take weight of null edge");
    if (matrix[w.v1()][w.v2()] == 0) return Integer.MAX_VALUE;
    else return matrix[w.v1()][w.v2()];
  }

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

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