/* HashFinder.java -- finds the hash character.
   Copyright (C) 2006 Free Software Foundation

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.
*/


package gnu.classpath.tools.rmic;

import java.util.HashSet;

/**
 * This class finds the hash character (the most different character in
 * the passed array of strings). This character is used to accelerate the
 * method invocation by name.
 *
 * @author Audrius Meskauskas (AudriusA@Bioinformatics.org) 
 */
public class HashFinder
{
   /**
   * Find the hash char position in the given collection of strings.
   * 
   * @param strings the string collection
   * 
   * @return the optimal hash character position, always less then the
   * length of the shortest string.
   */
  public int findHashCharPosition(String[] strings)
  {
    // Find the length of the shortest string:

    int l = strings[0].length();
    for (int i = 1; i < strings.length; i++)
      {
        if (strings[i].length() < l)
          l = strings[i].length();
      }

    // Find the position with the smallest number of the matching characters:
    HashSet[] charLists = new HashSet[l];

    for (int i = 0; i < charLists.length; i++)
      {
        charLists[i] = new HashSet(strings.length);
      }

    for (int i = 0; i < strings.length; i++)
      for (int p = 0; p < l; p++)
        {
          charLists[p].add(new Integer(strings[i].charAt(p)));
        }
    
    int m = 0;
    int v = charLists[0].size();
    
    for (int i = 1; i < charLists.length; i++)
      {
        // Replace on equality also, seeking the hash char closer to the end
        // of line.
        if (charLists[i].size()>=v)
          {
            m = i;
            v = charLists[i].size();
          }
      }
    return m;
  }
}