Поки що не фіналізований метод.

3-wayQuickSort.m

- (void)sortArray:(NSMutableArray *)array withLeft:(NSInteger )left andRight:(NSInteger )right
{
	NSInteger i = left - 1;
	NSInteger j = right;
	NSInteger p = left - 1;
	NSInteger q = right;
	
	if (right <= left)
		return;
	
	id v = array[right];
	
	for (; ; )
	{
		while ([array[++i] compare:v] == NSOrderedAscending);
		while ([v compare:array[--j]] == NSOrderedAscending)
			if (j == left) break;
		if (i >= j) break;
		
		[array exchangeObjectAtIndex:i withObjectAtIndex:j];
		
		if ([array[i] compare:v] == NSOrderedSame)
		{
			p++;
			[array exchangeObjectAtIndex:p withObjectAtIndex:i];
		}
		
		if ([v compare:array[j]] == NSOrderedSame)
		{
			q--;
			[array exchangeObjectAtIndex:j withObjectAtIndex:q];
		}
	}
	
	[array exchangeObjectAtIndex:i withObjectAtIndex:right];
	
	j = i - 1;
	i = i + 1;
	
	for (int k = left; k < p; k++)
	{
		[array exchangeObjectAtIndex:k withObjectAtIndex:j--];
	}
	
	for (int k = right - 1; k > q; k--, i++)
	{
		[array exchangeObjectAtIndex:i withObjectAtIndex:k];
	}
	
	[self sortArray:array withLeft:left andRight:j];
	[self sortArray:array withLeft:i andRight:right];
}