Bubble sort implementation in c#

Question

Here's how to implement a bubble sort in c#.

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int[] array = { 108, 23, 69, 420, 9 };
int temporary;

for (int j = 0; j <= array.Length - 2; j++)
{
    for (int i = 0; i <= array.Length - 2; i++)
    {
        if (array[i] > array[i + 1])
        {
            temporary= array[i + 1];
            array[i + 1] = array[i];
            array[i] = temporary;
        }
    }
}

Console.WriteLine("Sorted:");
foreach (int p in array)
{
    Console.Write($"{p} ");
}
Console.ReadLine();

Answer 1

while it returns the correct result, it is not correct. there is no need to process the last element as the exchange has already happened and you are reprocessing swapped items:

int[] array = { 108, 23, 69, 420, 9 };

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

Console.WriteLine("Sorted:");

foreach (int p in array)
{
    Console.WriteLine(p);
}

and with early exit optimization:

int[] array = { 108, 23, 69, 420, 9};

for (int j = 0; j < array.Length - 1; j++)
{
	bool swapped = false;
    for (int i = 0; i < array.Length - j - 1; i++)
    {
        if (array[i] > array[i + 1])
        {
            int temporary = array[i + 1];
            array[i + 1] = array[i];
            array[i] = temporary;
			swapped = true;
        }
    }
	if (swapped == false)
       break;
}

Answer 2

Very nice code! Well done :)

However, your implementation is wrong, because instead of array.length -2 it should be one:

First for loop: array.length

On the other hand:

Second for loop: array.length -1

It would not sort the whole array if you wrote it like this.

But otherwise good code!

Answer 3

So the correct solution should look like this, for everyone searching for a correct algorithm:

int[] array = { 108, 23, 69, 420, 9 };
int temporary;

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

Console.WriteLine("Sorted:");

foreach (int p in array)
{
    Console.WriteLine(p);
}

Console.ReadLine();

Or complementary for the logical operator <= like implemented above:

int[] array = { 108, 23, 69, 420, 9 };
int temporary;

for (int j = 0; j <= array.Length - 1; j++)
{
    for (int i = 0; i <= array.Length - 2; i++)
    {
        if (array[i] > array[i + 1])
        {
            temporary = array[i + 1];
            array[i + 1] = array[i];
            array[i] = temporary;
        }
    }
}

Console.WriteLine("Sorted:");
foreach (int p in array)
{
    Console.WriteLine(p);
}
Console.ReadLine();