/* From: "COMPUTATIONAL PHYSICS, 2nd Ed" 
   by RH Landau, MJ Paez, and CC Bordeianu 
   Copyright Wiley-VCH, 2007.
   Electronic Materials copyright: R Landau, Oregon State Univ, 2007;
   MJ Paez, Univ Antioquia, 2007; and CC Bordeianu, Univ Bucharest, 2007.
   Support by National Science Foundation                              
   */
// COLUMN/java:  Column growth simulation

import java.io.*;                          // Location of PrintWriter
import java.util.*;                             // Location of Random
import java.lang.*;                               // Location of Math

public class COLUMN  {
 
  public static void main(String[] argv) throws IOException, 
                                         FileNotFoundException    {
	  PrintWriter q = new PrintWriter(                     // Data file
			           new FileOutputStream("COLUMN.DAT"),true);
                 
                // Initialize 48 bit pseudo-random number generator:
    long seed = 971761;          //Different seed, different sequence
	  Random randnum = new Random(seed); 
              	// To access next random double: randnum.nextDouble()
                
    int max = 100000, npoints = 200;       // Iterations, open spaces
    int i = 0, dist = 0, r = 0, x = 0, y = 0, oldx = 0, oldy = 0;
	  double pp = 0.0, prob = 0.0;
	  int hit[] = new int[200];
	  for (i = 0; i<npoints; i++) hit[i] = 0;            // Clear array
	  oldx = 100;
	  oldy = 0;
	  for (i = 1;i<=max;i++)  {
		  r = (int)(npoints*randnum.nextDouble());
		  x = r-oldx;
		  y = hit[r]-oldy;
		  dist = x*x+y*y;
		  if(dist == 0) prob = 1.0;                   // Prob of sticking
		  else prob = 9.0/dist;                      //nu = -2.0, c = 0.9
		  pp = randnum.nextDouble();
		  if (pp < prob) {
			  if (r>0 && r<(npoints-1)) {
			  	if ((hit[r] >= hit[r-1]) && (hit[r] >= hit[r+1])) hit[r]++;
			  	else if ( hit[r-1] > hit[r+1] ) hit[r] = hit[r-1];
				  else hit[r] = hit[r+1];
				  oldx = r;
				  oldy = hit[r];
				  q.println(r+"  "+hit[r]);
			  }
      }
    }
	  System.out.println(" ");
	  System.out.println("COLUMN Program Complete.");
	  System.out.println("Data stored in COLUMN.DAT");
	  System.out.println(" ");
  }
}   // End of class