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Visualization and comparison of sorting algorithms in C#

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30 Mar 2016CPOL9 min read 50.5K   2.4K   69   9
This is an alternative for "Visualization and comparison of sorting algorithms in C#"

In this article, I introduce you to an updated version of Kanasz Robert's "Sort Comparison" project.

Image 1

Table Of Contents

Introduction

This is an update to the excellent work of Kanasz Robert, in which he presented a project which visualizes and compares sorting algorithms. It also contains the NGIF project, which can be used to save these visualizations as GIF files. This program allows the user to choose two of many sorting algorithms and compare them visually, with varying sizes and types of data sets and at varying speeds. It also allows the user to create GIF files of the visualizations.

Sorting Algorithms

Mr. Robert did a great job of explaining how many sorting algorithms work, so please see his article for that.

In this version, Bucket Sort was removed because the code functionally matched Pigeonhole Sort. Also, "Quicksort with Bubble Sort" was changed to "Quicksort with Insertion Sort" because Insertion Sort performs better than Bubble Sort. Five algorithms were added: Counting Sort, Merge Sort (Double Storage), Radix Sort, Smoothsort, and Timsort.

Counting Sort

Image 2

Counting Sort, similar to Pigeonhole Sort, is a sorting algorithm which is not a comparison sort, so it uses about 2n comparisons (for finding the minimum and maximum in the first pass) when sorting the data. This allows it to be extremely fast, with its drawbacks being that the data needs to be integers and the range needs to be small. It works by going through the data the first time, finding the minimum and maximum to determine the range. Then it creates a new array with that range and goes through the data again, counting how many of each element it finds. Finally, it goes through this new array and writes the data, sorted, to the original array. Admittedly, some code for this sort was already in the project, it just didn't make it into Mr. Robert's original article.

// super-fast, but it requires the data to have a small amount of variation (ideally n or less)
public IList CountingSort(IList arrayToSort)
{
    object min = null;
    object max = null;

    SetItem(arrayToSort, ref min, 0);
    SetItem(arrayToSort, ref max, 0);

    // start at 1 because we're already considering 0
    for (int i = 1; i < arrayToSort.Count; i++)
    {
        if (CompareItems(arrayToSort, i, min) < 0)
        {
            SetItem(arrayToSort, ref min, i);
        }
        else if (CompareItems(arrayToSort, i, max) > 0)
        {
            SetItem(arrayToSort, ref max, i);
        }
    }

    int range = (int)max - (int)min + 1;

    // reserve space to store the array in a different form
    int[] count = new int[range];

    for (int i = 0; i < range; i++)
    {
        count[i] = 0;
    }

    for (int i = 0; i < arrayToSort.Count; i++)
    {
        count[(int)GetItem(arrayToSort, i) - (int)min]++;
    }

    // now create the original array in sorted order
    int z = 0;
    for (int i = 0; i < count.Length; i++)
    {
        while (count[i] > 0)
        {
            SetItem(arrayToSort, z, (object)(i + (int)min));
            z++;
            count[i]--;
        }
    }

    return arrayToSort;
}
Worst case performance: O(n)
Best case performance: O(n)
Average case performance: O(n)
Worst case space complexity: max(N) - min(N) auxiliary

Merge Sort Double Storage

Image 3

Merge Sort is a sorting algorithm which uses a divide-and-conquer recursion to sort small partitions and then combine those partitions into larger ones. The Double Storage version outperforms the In Place version significantly, but uses much more space to do so. It is very fast and competes with Quicksort in speed. When it divides the data down to partitions of size 1 or 0, it can stop recursing because the data of that size is sorted. It then combines the data of two partitions by comparing the first elements of the partitions and writing the smaller element to a new List. Once one of the partitions has been traversed, it can copy the rest of the other partition to the List and return the List as a sorted copy of that range of data, to be merged at the next level up.

// a fast sort with n extra storage
public IList MergeSortDoubleStorage(IList a, int low, int high)
{
    int l = low;
    int h = high;

    // sorted when down to one element
    IList r = new ArrayList();
    if (l == h)
    {
        r.Add(GetItem(a, low));
        return r;
    }
    else if (l > h)
    {
        return r; // empty
    }

    int mid = (l + h) / 2;
    IList firstList = MergeSortDoubleStorage(a, l, mid);
    IList secondList = MergeSortDoubleStorage(a, mid + 1, h);

    // combine the lists
    int startFirst = 0;
    int startSecond = 0;
    int i = l;

    // create a new array combining the smaller two
    while (startFirst < firstList.Count && startSecond < secondList.Count && i <= h)
    {
        // penalty for comparing two objects
        operationCount++;

        if (((IComparable)firstList[startFirst]).CompareTo(secondList[startSecond]) < 0)
        {
            r.Add(firstList[startFirst]);

            // also overwrite the original array (for visuals - in practice, just replace the original array with the new sorted array)
            SetItem(a, i, firstList[startFirst]);

            startFirst++;
            i++;
        }
        else
        {
            r.Add(secondList[startSecond]);

            // also overwrite the original array (for visuals - in practice, just replace the original array with the new sorted array)
            SetItem(a, i, secondList[startSecond]);

            startSecond++;
            i++;
        }
    }

    // add the rest of the list (one is finished)
    while (startFirst < firstList.Count && i <= h)
    {
        r.Add(firstList[startFirst]);

        // also overwrite the original array (for visuals - in practice, just replace the original array with the new sorted array)
        SetItem(a, i, firstList[startFirst]);

        startFirst++;
        i++;
    }
    while (startSecond < secondList.Count && i <= h)
    {
        r.Add(secondList[startSecond]);

        // also overwrite the original array (for visuals - in practice, just replace the original array with the new sorted array)
        SetItem(a, i, secondList[startSecond]);

        startSecond++;
        i++;
    }

    return r;
}
Worst case performance: O(n log n)
Best case performance: O(n log n)
Average case performance: O(n log n)
Worst case space complexity: O(n) auxiliary

 

Radix Sort

Image 4

Radix Sort is a non-comparitive integer sorting algorithm which works very fast and can even beat Quicksort. Its main drawback is that it only compares positive integers, although there are versions of it which allow for negative numbers and others for floating point data. It works by copying/moving the the data into specific buckets, based on the value of its least significant bits or digits. It then copies/moves the data back into the original array and iterates again, looking at the next least significant bits or digits. The number of buckets used depends on the number of bits considered in each iteration. If it looks at 8 bits at a time, it uses 256 buckets, one for each combination of 8 0's and 1's.

// requires all data to be positive integers (this version), but sorts in O(n) time (the 16-bit version sorts in 2 read passes and 2 write passes and finishes much faster than Quicksort)
// in practice, 16-bit version doesn't do much better than 8-bit version (in visualization, it makes a HUGE difference)
// this is comparable to Pigeonhole Sort, but without the variability restriction (this makes set number of buckets depending on which version - 8-bit version makes 256 buckets)
public IList RadixSort(IList array)
{
    // based on http://algorithmsandstuff.blogspot.com/2014/06/radix-sort-in-c-sharp.html and https://en.wikibooks.org/wiki/Algorithm_Implementation/Sorting/Radix_sort#C.23_least_significant_digit_.28LSD.29_radix_sort_implementation
    int shift = 0;
    int totalBits = 32; // 32 bits for int

    // decide how many bits to look at during each round (and how many buckets to use)
    //int maskLength = 16; // totalBits must be evenly divided by this
    //int mask = 65535; // 16 bits, all 1's; this many buckets may seem like overkill, but when you have 1 million items to sort, it makes much more sense

    int maskLength = 8; // totalBits must be evenly divided by this (don't use 6 or 10)
    int mask = 255; // 8 bits, all 1's

    //int maskLength = 1;
    //int mask = 1; // 1 bit at a time

    List<Queue<int>> buckets = new List<Queue<int>>();
    for (int i = 0; i <= mask; i++) // exponentially more buckets based on how many bits are being checked - so we can't just use 32 bits
    {
        Queue<int> q = new Queue<int>();
        buckets.Add(q);
    }

    // look at every bit of every item
    while (shift < totalBits)
    {
        int i;

        // put every item into a bucket based on its lowest bits, then the next lowest bits, and so on
        for (i = 0; i < array.Count; i++)
        {
            int bucketNumber = ((int)GetItem(array, i) >> shift) & mask;

            buckets[bucketNumber].Enqueue((int)GetItem(array, i));
        }

        i = 0;
        // put all items back into the array, lowest buckets first, first-in-first-out
        foreach (Queue<int> bucket in buckets)
        {
            while (bucket.Count > 0)
            {
                SetItem(array, i, (object)bucket.Dequeue());
                i++;
            }
        }

        shift += maskLength;
    }

    return array;
}
Worst case performance: O(n)
Best case performance: O(n)
Average case performance: O(n)
Worst case space complexity: O(n) auxiliary

 

Smoothsort

Image 5

Smoothsort is a version of Heapsort which adapts better to data which is sorted or nearly sorted. Like Heapsort, it builds a heap from the data and then moves the largest item to the end and fixes the heap. A heap is a binary tree where each parent is larger than both of its two children. It works quickly because a heap can be built and fixed quickly. The difference is in how the heap is built within the array. It's more complicated than I dare to understand, but you can find more information in the Wikipedia article and another CodeProject article, "Fastest In-Place Stable Sort", which is where the code is ported from.

The code is about 560 lines, so please download the project to see it. 

Worst case performance: O(n log n)
Best case performance: O(n)
Average case performance: O(n log n)
Worst case space complexity: O(1) auxiliary

 

Timsort

Image 6

Timsort is a hybrid sorting algorithm, derived from Merge Sort and Insertion Sort. It's so fast that it's used in Java, Python, and Android. It's designed to work well with real-world data, which tends to have runs of ascending or descending data in it. It works by finding these runs, creating runs (sorting) where there aren't runs, and merging them together. It is also more complicated than I dare to understand, but you can find more information in the Wikipedia article and this code, which I used to create my own version. My code usually works, but it's definitely bugged, so if you can debug it, please let me know.

The code is about 826 lines, so please download the project to see it.

Worst case performance: O(n log n)
Best case performance: O(n)
Average case performance: O(n log n)
Worst case space complexity: O(n) auxiliary

Types Of Data Sets

Also useful to know is how different algorithms perform on different types of data sets.  For example, Bubble Sort, which is known for its poor performance, does better than Quicksort on sorted data. This is not to say Bubble Sort should be used, it's just an interesting fact, clearly shown in a visualization.

Image 7 Image 8
Bubble Sort Quicksort

These other types of data sets can also be used to look for worst cases for some sorts, which may cause you to choose not to use the algorithm. For example, let's look at each type of data and compare Quicksort with Timsort, two widely used algorithms.

Random
Image 9 Image 10
Quicksort Timsort

 

Reversed
Image 11 Image 12
Quicksort Timsort

 

Sorted
Image 13 Image 14
Quicksort Timsort

 

Nearly Sorted
Image 15 Image 16
Quicksort Timsort

 

Few Unique
Image 17 Image 18
Quicksort Timsort

 

As you can see in these comparisons, they are both very competitive, with Timsort having the advantage in sorting Sorted data. Still, I'm partial to Quicksort because of its relative simplicity and smaller space requirements.

To provide these types of data sets, I just added a combo box and this code:

// this part is done within a call to PrepareForSort();
array1 = new ArrayList(tbSamples.Value);
array2 = new ArrayList(tbSamples.Value);
for (int i = 0; i < array1.Capacity; i++)
{
    int y = (int)((double)(i + 1) / array1.Capacity * pnlSort1.Height);
    array1.Add(y);
}
            
// this part is done within a call to Randomize(array1);
for (int i = array1.Count - 1; i > 0; i--)
{
    int swapIndex = rand.Next(i + 1);
    if (swapIndex != i)
    {
        object tmp = array1[swapIndex];
        array1[swapIndex] = array1[i];
        array1[i] = tmp;
    }
}

array2 = (ArrayList)array1.Clone();

// the rest is done in cmdSort_Click
if (ddTypeOfData.SelectedItem.ToString() == "Random")
{
    // ready to go
}
else if (ddTypeOfData.SelectedItem.ToString() == "Sorted")
{
    array1.Sort();
    array2 = (ArrayList)array1.Clone();
}
else if (ddTypeOfData.SelectedItem.ToString() == "Nearly Sorted")
{
    array1.Sort();

    int maxValue = array1.Count / 10;

    // move anywhere from 2 items to 20% of the items
    int itemsToMove = rand.Next(1, maxValue);
    for (int i = 0; i < itemsToMove; i++)
    {
        int a = rand.Next(0, array1.Count);
        int b = rand.Next(0, array1.Count);

        while (a == b)
        {
            a = rand.Next(0, array1.Count);
            b = rand.Next(0, array1.Count);
        }

        object temp = array1[a];
        array1[a] = array1[b];
        array1[b] = temp;
    }

    array2 = (ArrayList)array1.Clone();
}
else if (ddTypeOfData.SelectedItem.ToString() == "Reversed")
{
    array1.Sort();
    array1.Reverse();

    array2 = (ArrayList)array1.Clone();
}
else if (ddTypeOfData.SelectedItem.ToString() == "Few Unique")
{
    int maxValue = 10;

    if (array1.Count < 100)
        maxValue = 6;

    // choose a random amount of unique values
    maxValue = rand.Next(2, maxValue);

    ArrayList temp = new ArrayList();
    for (int i = 0; i < maxValue; i++)
    {
        int y = (int)((double)(i + 1) / maxValue * pnlSort1.Height);
        temp.Add(y);
    }

    for (int i = 0; i < array1.Count; i++)
    {
        array1[i] = temp[rand.Next(0, maxValue)];
    }

    array2 = (ArrayList)array1.Clone();
}

Visualization Overhaul

Mr. Robert did a great job of setting up a way to visualize the sorting algorithms, but as I worked with the code, I eventually decided to overhaul how it worked. The first change was to highlight in red the action taking place on the data, whether that's a comparison or a change in the data. Second, I made the drawing procedure draw rectangles instead of lines if there was room them, so that the data was more pleasing to the eye. Next, rather than having a system which does an operation, then waits for a specific period of time, I set it up so that it would do a specific number of operations per second, with new images drawn about 25 times per second. This allowed for larger data sets and faster visualizations. I also modified the code to allow different sizes of visualizations, so that the user can maximize the window to get a better view of the data and the action on that data.

Putting all of these together, we add/modify this code in the SortAlgorithm class:

int operationsPerFrame; // operations per frame
int frameMS; // time between frames (aim for 40 ms = 25 fps)
int operationCount;
Dictionary<int, bool> highlightedIndexes = new Dictionary<int, bool>(); // highlight all of these indexes in the frame
DateTime nextFrameTime;
int originalPanelHeight;

public SortAlgorithm(ArrayList list, PictureBox pic, bool sp, string of, int s, string outFile)
{
    imgCount = 0;
    arrayToSort = list;
    pnlSamples = pic;
    savePicture = sp;
    outputFolder = of;
    outputFile = outFile;

    operationCount = 0;
    operationsPerFrame = s;
    frameMS = 1000; // so now operationsPerFrame is operations per second

    // reduce the frame wait for better visuals (increased frame rate)
    while (frameMS >= 40 && operationsPerFrame > 1)
    {
        operationsPerFrame = operationsPerFrame / 2;
        frameMS = frameMS / 2;
    }

    bmpsave = new Bitmap(pnlSamples.Width, pnlSamples.Height);
    g = Graphics.FromImage(bmpsave);
    originalPanelHeight = pnlSamples.Height;
    pnlSamples.Image = bmpsave;
    nextFrameTime = DateTime.UtcNow;

    checkForFrame();
}

private void checkForFrame()
{
    if (operationCount >= operationsPerFrame || nextFrameTime <= DateTime.UtcNow)
    {
        // time to draw a new frame and wait
        DrawSamples();
        RefreshPanel(pnlSamples);
        if (savePicture)
            SavePicture();

        // prepare for next frame
        highlightedIndexes.Clear();
        operationCount -= operationsPerFrame; // if there were more operations than needed, don't just forget those

        if (DateTime.UtcNow < nextFrameTime)
        {
            Thread.Sleep((int)((nextFrameTime - DateTime.UtcNow).TotalMilliseconds));
        }
        nextFrameTime = nextFrameTime.AddMilliseconds(frameMS);
    }
}

public void finishDrawing()
{
    if (highlightedIndexes.Count > 0)
    {
        // put one last frame in before the end
        nextFrameTime = DateTime.UtcNow;
        checkForFrame();
    }

    // draw the last frame
    nextFrameTime = DateTime.UtcNow;
    checkForFrame();
}

public void DrawSamples()
{
    // might need to grow or shrink if size is different from original (can't change array!)
    double multiplyHeight = 1;

    // check if need to change size
    if (bmpsave.Width != pnlSamples.Width || bmpsave.Height != pnlSamples.Height)
    {
        bmpsave = new Bitmap(pnlSamples.Width, pnlSamples.Height);
        g = Graphics.FromImage(bmpsave);
        pnlSamples.Image = bmpsave;
    }

    if (pnlSamples.Height != originalPanelHeight)
    {
        multiplyHeight = (double)(pnlSamples.Height) / (double)(originalPanelHeight);
    }

    // start with white background
    g.Clear(Color.White);

    // use black sometimes
    Pen pen = new Pen(Color.Black);
    SolidBrush b = new SolidBrush(Color.Black);

    // use red sometimes
    Pen redPen = new Pen(Color.Red);
    SolidBrush redBrush = new SolidBrush(Color.Red);
         
    // draw a nice width based on number of elements         
    int w = (pnlSamples.Width / arrayToSort.Count) - 1;

    for (int i = 0; i < this.arrayToSort.Count; i++)
    {
        int x = (int)(((double)pnlSamples.Width / arrayToSort.Count) * i);

        int itemHeight = (int)Math.Round(Convert.ToDouble(arrayToSort[i]) * multiplyHeight);

        // draw highlighed versions
        if (highlightedIndexes.ContainsKey(i))
        {
            if (w <= 1)
            {
                g.DrawLine(redPen, new Point(x, pnlSamples.Height), new Point(x, (int)(pnlSamples.Height - itemHeight)));
            }
            else
            {
                g.FillRectangle(redBrush, x, pnlSamples.Height - itemHeight, w, pnlSamples.Height);
            }
        }
        else // draw normal versions
        {
            if (w <= 1)
            {
                g.DrawLine(pen, new Point(x, pnlSamples.Height), new Point(x, (int)(pnlSamples.Height - itemHeight)));
            }
            else
            {
                g.FillRectangle(b, x, pnlSamples.Height - itemHeight, w, pnlSamples.Height);
            }
        }
    }
}

 

Unified Get, Set, Swap and Compare Functions

In order to make new sorting algorithms easier to add, easier to read, and easier to illustrate, I created the functions needed for illustrating any compare, swap, set, or get. These added the appropriate number of operations and called checkForFrame() to draw a new image if necessary.

private object GetItem(IList arrayToSort, int index)
{
    if (!highlightedIndexes.ContainsKey(index))
        highlightedIndexes.Add(index, false);

    operationCount++;
    checkForFrame();

    return arrayToSort[index];
}
private void SetItem(IList arrayToSort, int toIndex, int fromIndex)
{
    arrayToSort[toIndex] = arrayToSort[fromIndex];

    if (!highlightedIndexes.ContainsKey(toIndex))
        highlightedIndexes.Add(toIndex, false);

    operationCount++;
    checkForFrame();
}
private void SetItem(IList arrayToSort, int toIndex, object fromObject)
{
    arrayToSort[toIndex] = fromObject;

    if (!highlightedIndexes.ContainsKey(toIndex))
        highlightedIndexes.Add(toIndex, false);

    operationCount++;
    checkForFrame();
}
private void SetItem(IList arrayToSort, ref object toObject, int fromIndex)
{
    toObject = arrayToSort[fromIndex];

    if (!highlightedIndexes.ContainsKey(fromIndex))
        highlightedIndexes.Add(fromIndex, false);

    operationCount++;
    checkForFrame();
}
private void SwapItems(IList arrayToSort, int index1, int index2)
{
    object temp = arrayToSort[index1];
    arrayToSort[index1] = arrayToSort[index2];
    arrayToSort[index2] = temp;

    if (!highlightedIndexes.ContainsKey(index1))
        highlightedIndexes.Add(index1, false);
    if (!highlightedIndexes.ContainsKey(index2))
        highlightedIndexes.Add(index2, false);

    operationCount += 2;
    checkForFrame();
}
private int CompareItems(IList arrayToSort, int index1, int index2)
{
    if (!highlightedIndexes.ContainsKey(index1))
        highlightedIndexes.Add(index1, false);
    if (!highlightedIndexes.ContainsKey(index2))
        highlightedIndexes.Add(index2, false);

    operationCount++;
    checkForFrame();

    return ((IComparable)arrayToSort[index1]).CompareTo(arrayToSort[index2]);
}
private int CompareItems(IList arrayToSort, int index1, object o)
{
    if (!highlightedIndexes.ContainsKey(index1))
        highlightedIndexes.Add(index1, false);

    operationCount++;
    checkForFrame();

    return ((IComparable)arrayToSort[index1]).CompareTo(o);
}
private int CompareItems(IList arrayToSort, object o, int index1)
{
    if (!highlightedIndexes.ContainsKey(index1))
        highlightedIndexes.Add(index1, false);

    operationCount++;
    checkForFrame();

    return ((IComparable)o).CompareTo(arrayToSort[index1]);
}

 

Points Of Interest

I became interested in this project after seeing visualizations of sorting algorithms on YouTube and at http://www.sorting-algorithms.com/. In parallel to this, I also have a project which, rather than drawing images, instead sorts, counts operations, and is a timer for the algorithms as they race to sort the data. I was surprised to learn that, after implementing every version of Quicksort I could find, nothing improves (much) on this basic version. The tri-median method does about the same. And the 3-partition version seems to be solving a problem that doesn't really exist. Quicksort does Few Unique types of data faster than Random types of data, so it's not really an issue. I did change the pivot to be random so that it won't come across some worst case set of data and end up with an n2 sorting time. So here's that beautiful, simple function.

// a fast sort with log2(n) extra storage
public IList Quicksort(IList a, int left, int right)
{
    int i = left;
    int j = right;

    object x = null;
    SetItem(a, ref x, rand.Next(left, right + 1));

    // find items to swap so smaller items are on the left side and larger items are on the right side
    while (i <= j) // when i=j, need to compare to know which way to move (left or right)
    {
        while (CompareItems(a, i, x) < 0)
        {
            i++;
        }
        while (CompareItems(a, x, j) < 0)
        {
            j--;
        }

        if (i < j)
        {
            SwapItems(a, i, j);
            i++;
            j--;
        }
        else if (i == j) // no need to swap in this case
        {
            i++;
            j--;
        }
    }

    // now everything from left to j is less than or equal to the pivot
    // and everything from i to right is greater than or equal to the pivot
    // note that we don't need to push the pivot in between these partitions to be fast
    if (left < j)
    {
        Quicksort(a, left, j);
    }
    if (i < right)
    {
        Quicksort(a, i, right);
    }

    return a;
}

 

Also of interest to me was the sorting algorithm Shellsort, which is such a simple concept to understand and performs nearly as well as Quicksort when you've only got 1000 items or less to sort.

Image 19 Image 20
Quicksort Shellsort

 

Amusing Visualizations

Some visualizations were surprisingly interesting. For example, watch Bidirectional Bubble Sort actually appear to be a shrinking bubble. Note that this is a very slow sort shown at a high speed.

Image 21
Bidirectional Bubble Sort

 

Odd-Even Sort looks just like Bubble Sort, which is a data set moving to the right, except that it's two data sets, with one (too large items) moving right and the other (too small items) moving left.

Image 22 Image 23
Bubble Sort Odd-Even Sort

 

And finally, Radix Sort's data starts to have a distinct look if you use a wide enough set of data and/or a small enough number of bits/buckets. This is the 8-bit version working on data ranging from 1 to int.MaxValue. The normal version of this program does not allow such a range, in order to accomodate Pigeonhole Sort and Counting Sort.

Image 24
Radix Sort

 

History

3/30/2016 - Initial version

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


Written By
United States United States
Mark has been a professional programmer since 2008 working mainly in ASP.NET applications, using C#, VB.NET, and Microsoft SQL Server. He's also proficient in HTML, Javascript, MySQL, VB6, C++, and Oracle.

Comments and Discussions

 
Questionbest in class Pin
Member 367915214-Jan-18 1:00
Member 367915214-Jan-18 1:00 
GeneralSuperb! Pin
Stephen Gonzalez26-Oct-16 12:54
Stephen Gonzalez26-Oct-16 12:54 
GeneralNice one! Pin
Member 1253487019-May-16 20:37
Member 1253487019-May-16 20:37 
GeneralSuperb Pin
aarif moh shaikh7-May-16 0:07
professionalaarif moh shaikh7-May-16 0:07 
Praisevery nice Pin
BillW3322-Apr-16 4:01
professionalBillW3322-Apr-16 4:01 
GeneralMy vote of 5 Pin
John Underhill14-Apr-16 6:17
John Underhill14-Apr-16 6:17 
SuggestionStable sorting Pin
jnm21-Apr-16 1:18
jnm21-Apr-16 1:18 
GeneralRe: Stable sorting Pin
Mark Monnin1-Apr-16 2:51
Mark Monnin1-Apr-16 2:51 
GeneralMy vote of 5 Pin
Franc Morales31-Mar-16 1:01
Franc Morales31-Mar-16 1:01 

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