/* File: RandomGridGraph.java - May 2011 */
package l25;

/**
 *  Represent a random weighted graph on the 2D grid. Various
 *  parameters can be set to adjust the maximum edge weight, and the
 *  extent to which vertical edges and horizontal edges differ in weight.
 *
 *  @author Michael Albert
 *
 */

public class RandomGridGraph extends Graph{

   static int MAX_WEIGHT = 1000000;
   static double VERTICAL_BIAS = 1.0;

   int rows;
   int cols;
 
   public RandomGridGraph(int rows, int cols) {
      this(rows, cols, MAX_WEIGHT, VERTICAL_BIAS);
   }

   public RandomGridGraph(int rows, int cols, int maxWeight) {
      this(rows, cols, maxWeight, VERTICAL_BIAS);
   }

   public RandomGridGraph(
                          int rows, 
                          int cols, 
                          int maxWeight, 
                          double verticalBias
                          ) {

      super(rows*cols);
      this.rows = rows;
      this.cols = cols;
      MAX_WEIGHT = maxWeight;
      VERTICAL_BIAS = verticalBias;

      initialise();

   }

   public void initialise() {
      removeEdges();
      // Vertical edges
      for(int r = 0; r < rows-1; r++) {
         for(int c = 0; c < cols; c++) {
            addWeightedEdge(
                              r*cols + c, 
                              (r+1)*cols+c, 
                              (int) (VERTICAL_BIAS*getWeight())
                              );
         }
      }

      // Horizontal edges
      for(int r = 0; r < rows; r++) {
         for(int c = 0; c < cols-1; c++) {
            addWeightedEdge(r*cols + c, r*cols+c+1, getWeight());
         }
      }
   }


   static int getWeight() {
      return 1 + (int) (Math.random()*MAX_WEIGHT);
   }
      
}