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/* mergesort.vala
*
* Copyright (C) 2009 Didier Villevalois
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
* This library 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
* Lesser General Public License for more details.
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Author:
* Will <tcosprojects@gmail.com>
*/
internal class Gee.MergeSort<G> {
public static void sort<G> (List<G> list, CompareFunc compare) {
if (list is ArrayList) {
MergeSort.sort_arraylist<G> ((ArrayList<G>) list, compare);
} else {
MergeSort.sort_list<G> (list, compare);
}
}
public static void sort_list<G> (List<G> list, CompareFunc compare) {
MergeSort<G> helper = new MergeSort<G> ();
helper.list_collection = list;
helper.array = list.to_array ();
helper.list = helper.array;
helper.index = 0;
helper.size = list.size;
helper.compare = compare;
helper.do_sort ();
// TODO Use a list iterator and use iter.set(item)
list.clear ();
foreach (G item in helper.array) {
list.add (item);
}
}
public static void sort_arraylist<G> (ArrayList<G> list, CompareFunc compare) {
MergeSort<G> helper = new MergeSort<G> ();
helper.list_collection = list;
helper.list = list._items;
helper.index = 0;
helper.size = list._size;
helper.compare = compare;
helper.do_sort ();
}
private List<G> list_collection;
private G[] array;
private unowned G[] list;
private int index;
private int size;
private CompareFunc compare;
private void do_sort () {
if (this.size <= 1) {
return;
}
var work_area = new G[this.size];
merge_sort_aux (index, this.size, work_area);
}
private void merge_sort_aux (int left, int right, G[] work_area) {
if (right == left + 1) {
return;
} else {
int size = right - left;
int middle = size / 2;
int lbegin = left;
int rbegin = left + middle;
merge_sort_aux (left, left + middle, work_area);
merge_sort_aux (left + middle, right, work_area);
for (int i = 0; i < size; i++) {
if (lbegin < left + middle && (rbegin == right ||
compare (list[lbegin], list[rbegin]) <= 0)) {
work_area[i] = list[lbegin];
lbegin++;
} else {
work_area[i] = list[rbegin];
rbegin++;
}
}
for (int i = left; i < right; i++) {
list[i] = work_area[i - left];
}
}
}
}
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