We have had 2 interns at work for the past few weeks and one of the tasks we gave them was to implement Quicksort. This got me to thinking about my youth and some of the code I wrote back then. I've decided to post it.

Here is one of my old implementations of Quicksort:

void Sort(int i, int j)
{
    T temp;

    if(i<j)
    {
        if(i == j-1) // 2 items
        {
            if(m_data[i] > m_data[j])
            {
                temp = m_data[i];
                m_data[i] = m_data[j];
                m_data[j] = temp;
            }
        }
        else if(i == j-2) // 3 items
        {
            if(m_data[i] > m_data[i+1])
            {
                temp = m_data[i];
                m_data[i] = m_data[i+1];
                m_data[i+1] = temp;
            }

            if(m_data[i+1] > m_data[i+2])
            {
                temp = m_data[i+1];
                m_data[i+1] = m_data[i+2];
                m_data[i+2] = temp;
            }

            if(m_data[i] > m_data[i+1])
            {
                temp = m_data[i];
                m_data[i] = m_data[i+1];
                m_data[i+1] = temp;
            }
        }
        else if(i == j-3) // 4 items
        {
            if(m_data[i] > m_data[i+1])
            {
                temp = m_data[i];
                m_data[i] = m_data[i+1];
                m_data[i+1] = temp;
            }

            if(m_data[i+1] > m_data[i+2])
            {
                temp = m_data[i+1];
                m_data[i+1] = m_data[i+2];
                m_data[i+2] = temp;
            }
        
            if(m_data[i+2] > m_data[i+3])
            {
                temp = m_data[i+2];
                m_data[i+2] = m_data[i+3];
                m_data[i+3] = temp;
            }

            if(m_data[i] > m_data[i+1])
            {
                temp = m_data[i];
                m_data[i] = m_data[i+1];
                m_data[i+1] = temp;
            }

            if(m_data[i+1] > m_data[i+2])
            {
                temp = m_data[i+1];
                m_data[i+1] = m_data[i+2];
                m_data[i+2] = temp;
            }

            if(m_data[i] > m_data[i+1])
            {
                temp = m_data[i];
                m_data[i] = m_data[i+1];
                m_data[i+1] = temp;
            }
        }
        else // 5 or more items
        {
            int pivot = j;
            int up = i-1;
            int down = pivot;

            while(up<down)
            {
                while((m_data[++up] < m_data[pivot]) && up<down);

                if(up>=down)
                    break;

                while((m_data[--down] > m_data[pivot]) && up<down);

                if(up>=down)
                    break;

                temp = m_data[up];
                m_data[up] = m_data[down];
                m_data[down] = temp;
            }

            temp = m_data[up];
            m_data[up] = m_data[pivot];
            m_data[pivot] = temp;
        
            Sort(i, up-1);
            Sort(up+1, j);
        }
    }
}

And here is another:

template<class T>
void CArray<T>::Sort(int (*Compare)(T &item1, T &item2), int left, int right)
{
    if(left >= right)
        return;

    int up = left-1;
    int down = right;
    int pivot = m_array[right];

    if(right == left + 1)
        if(Compare(m_array[left], m_array[right]) == 1)
        {
            Swap(left, right);
            return;
        }

    while(true)
    {
        while(Compare(m_array[++up], pivot) == -1 && up<down);
        while(Compare(m_array[--down], pivot) == 1 && up<down); 
        if(up>=down) break;
        Swap(up, down);
    }

    Swap(up, right);
    Sort(Compare, left, up-1);
    Sort(Compare, up+1, right);
}

The first example seems to be from 2004 and the second example seems to be from 2006, though I'm not sure how much I can actually trust the timestamps on the files. It is interesting to see how far I progressed in the timespan of about 2 years. 2004 would have been right in the middle of college and 2006 was torwards the end of my college time.

In the second example I think I had actually been a "professional" (aka I got paid a little money on the side) programmer for a few months. Like I said, I was young and stupid and I needed the money.