/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2007-2015 Broad Institute
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/*
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 * 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);
    }
}