QuickSort-Objective-C

QuickSort.m

void quicksortInPlace(NSMutableArray *array, NSInteger first, NSInteger last, NSComparator comparator) {
    if (first >= last) return;
    id pivot = array[(first + last) / 2];
    NSInteger left = first;
    NSInteger right = last;
    while (left <= right) {
        while (comparator(array[left], pivot) == NSOrderedAscending)
            left++;
        while (comparator(array[right], pivot) == NSOrderedDescending)
            right--;
        if (left <= right)
            [array exchangeObjectAtIndex:left++ withObjectAtIndex:right--];
    }
    quicksortInPlace(array, first, right, comparator);
    quicksortInPlace(array, left, last, comparator);
}
 
NSArray* quicksort(NSArray *unsorted, NSComparator comparator) {
    NSMutableArray *a = [NSMutableArray arrayWithArray:unsorted];
    quicksortInPlace(a, 0, a.count - 1, comparator);
    return a;
}