/*
 *  Copyright (C) 2009  E.Albert, P.Arenas, S.Genaim, G.Puebla, and D.Zanardini
 *                      https://costa.ls.fi.upm.es
 *
 *  This program 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 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package series;
/**
 * This class implements a sorting method based on the merge-sort algorithm.
 * 
 * 
 * @author E.Albert, P.Arenas, S.Genaim, and G.Puebla
 * 
 */
public class MergeSort {
        public void msort(int[] data) {
	    sort(data,0,data.length);
	}
	public void sort(int[] data, int from, int to) {
		int mid;

		if (from < to) {
			mid = (from + to) / 2;
			sort(data, from, mid);
			sort(data, mid + 1, to);
			merge(data, from, to, mid);
		}
	}

	public void merge(int[] data, int from, int to, int mid)	{

		int i, subListFrom = from, subListTo = mid + 1;
		int scratch[] = new int[data.length];

		// Merge two sorted sublists using a scratch array
		for (i = from; i <= to; i++) {
			if ((subListFrom <= mid) && ((subListTo > to) || data[subListFrom]>data[subListTo]))
				// (data.compare(subListFrom, subListTo) == data.at(subListTo))))
				scratch[i] = data[subListFrom++];
			else
				scratch[i] = data[subListTo++];
		}
		// Copy values stored in scratch array back
		for (i = from; i <= to; i++) {
			data[i]=scratch[i]; 
		}
	}
}