Logic behind a bubble sort

Question

I am doing a bubble sort exercise and my feeling is that it is very close to correct. As it is at the moment I am presented with an eternal loop.

Where does the fault lie ?

static void Main(string[] args)
    {
        int[] numbers = { 2, 4, 8, 5, 88, 55, 32, 55, 47, 8, 99, 120, 4, 32 };
        int temporary;
        bool sorted;
        do
        {
            sorted = false;

            for (int i = 0; i < numbers.Length - 1; i++)
            {
                int a = numbers[i];
                int b = numbers[i + 1];
                if (a > b)
                {
                    temporary = a;
                    a = b;
                    b = temporary;

                    sorted = true;

                }
            }
            Console.WriteLine("sorted");
        } while (sorted == true);


        foreach (int i in numbers)
        {
            Console.Write(i + " ");
        }

    }

Answer 1

A better approach in C# is to use a generic bubble sort

public void BubbleSort<T>(IList<T> list);
{
    BubbleSort<T>(list, Comparer<T>.Default);
}

public void BubbleSortImproved<T>(IList<T> list, IComparer<T> comparer)
{
    bool stillGoing = true;
    int k = 0;
    while (stillGoing)
    {
        stillGoing = false;
        for (int i = 0; i < list.Count - 1 - k; i++)
        {
            T x = list[i];
            T y = list[i + 1];
            if (comparer.Compare(x, y) > 0)
            {
                list[i] = y;
                list[i + 1] = x;
                stillGoing = true;
            }
        }
        k++;
    }
}

A brief explanation of this algorithm is given by Jon Skeet in his answer here. "It uses an arbitrary comparer, but lets you omit it in which case the default comparer is used for the relevant type. It will sort any (non-readonly) implementation of IList, which includes arrays."

I hope this helps.

Answer 2

You exchange a with b but you DON'T do anything to your input array. Thus, you are constantly exchanging values in memory but the original array is not changed. Try:

            for ( int i = 0; i < numbers.Length - 1; i++ )
            {
                if ( numbers[i] > numbers[i + 1] )
                {
                    temporary = numbers[i];
                    numbers[i] = numbers[i + 1];
                    numbers[i + 1] = temporary;

                    sorted = true;

                }
            }