/*
 * Copyright (c) 2007-2010 by The Broad Institute, Inc. and the Massachusetts Institute of Technology.
 * All Rights Reserved.
 *
 * This software is licensed under the terms of the GNU Lesser General Public License (LGPL), Version 2.1 which
 * is available at http://www.opensource.org/licenses/lgpl-2.1.php.
 *
 * THE SOFTWARE IS PROVIDED "AS IS." THE BROAD AND MIT MAKE NO REPRESENTATIONS OR WARRANTIES OF
 * ANY KIND CONCERNING THE SOFTWARE, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NONINFRINGEMENT, OR THE ABSENCE OF LATENT
 * OR OTHER DEFECTS, WHETHER OR NOT DISCOVERABLE.  IN NO EVENT SHALL THE BROAD OR MIT, OR THEIR
 * RESPECTIVE TRUSTEES, DIRECTORS, OFFICERS, EMPLOYEES, AND AFFILIATES BE LIABLE FOR ANY DAMAGES OF
 * ANY KIND, INCLUDING, WITHOUT LIMITATION, INCIDENTAL OR CONSEQUENTIAL DAMAGES, ECONOMIC
 * DAMAGES OR INJURY TO PROPERTY AND LOST PROFITS, REGARDLESS OF WHETHER THE BROAD OR MIT SHALL
 * BE ADVISED, SHALL HAVE OTHER REASON TO KNOW, OR IN FACT SHALL KNOW OF THE POSSIBILITY OF THE
 * FOREGOING.
 */

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package org.broad.igv.util;

import java.util.Comparator;
import java.util.List;

/**
 * @author jrobinso
 */
public class ArrayHeapObjectSorter<T> {

    private List<T> a;
    private int n;
    Comparator<T> c;

    public void sort(List<T> a0, Comparator<T> c) {
        a = a0;
        n = a.size();
        this.c = c;
        heapsort();
    }

    private void heapsort() {
        buildheap();
        while (n > 1) {
            n--;
            exchange(0, n);
            downheap(0);
        }
    }

    private void buildheap() {
        for (int v = n / 2 - 1; v >= 0; v--) {
            downheap(v);
        }
    }

    private void downheap(int v) {
        int w = 2 * v + 1;    // first descendant of v
        while (w < n) {
            if (w + 1 < n) // is there a second descendant?
            {
                if (c.compare(a.get(w + 1), a.get(w)) > 0) {
                    w++;
                }

            }
            // w is the descendant of v with maximum label

            if (c.compare(a.get(v), a.get(w)) >= 0) {
                return;  // v has heap property
            }            // otherwise

            exchange(v, w);  // exchange labels of v and w
            v = w;        // continue
            w = 2 * v + 1;
        }
    }

    private void exchange(int i, int j) {
        T t = a.get(i);
        a.set(i, a.get(j));
        a.set(j, t);
    }
}
