how can i sort a 2D int array in c#

Question

so i just started c# and found an exercise that says to sort the numbers in the array from small to big without using another array or change it to a 1D array this is what i did yet it does not work

     for (int i = 0; i < 3; i++)
        {
            for (int j = 0; j < 4; j++)
            {
                Min = test[i, j];
                int o = 0;
                lign = i;
                col = j;
                for (int h = i; h < 3; h++)
                {

                    for (int z = j; z < 4; z++)
                    {
                        if (test[h, z] < Min)
                        {
                            Min = test[h, z];
                            lign = h;
                            col = z;
                            o = 1;
                        }
                    }
                }
                if (o == 1)
                {
                    temp = test[i, j];
                    test[i, j] = test[lign, col];
                    test[lign, col] = temp;
                }

            }
        }

Answer 1

This should do the trick:

public int[,] Sort2DArray(int[,] input)
{
    int[] tempArray = new int[input.Length];
    Buffer.BlockCopy(input, 0, tempArray, 0, tempArray.Length * sizeof(int));

    Array.Sort(tempArray);

    int[,] output = new int[input.GetLength(0), input.GetLength(1)];
    Buffer.BlockCopy(tempArray, 0, output, 0, tempArray.Length * sizeof(int));

    return output;
}

The Buffer.BlockCopy calls take care of converting from a 2D array to a 1D array and vice versa. Once you've converted the array to 1D, sorting is trivial.

Answer 2

Based on your comment want to sort the 2d array completely (not row by row).

You have to tread your 2d array like 1d array. the sort algorithm I used is the simple bubble sort. but same logic can be used on some faster algorithms like quicksort

The trick is to convert a 1d index into 2d index. here is the simple extension method to get row and column from a 1d index based on column length.

/// <summary>
/// Calculates row and column index from given linear index and column length.
/// </summary>
/// <param name="index1D">linear index</param>
/// <param name="collength">column length</param>
/// <param name="row">returns index of row.</param>
/// <param name="col">returns index of column.</param>
public static void Get2DIndex(int index1D, int collength, out int row, out int col)
{
    row = index1D % collength;
    col = index1D / collength;
}

Now all you have to do is to iterate on 2d array like a normal array. you have 1d index and you calculate row and column using Get2DIndex

you have two for loops to do your bubble sort.

int[,] test = new int[4, 3]
{
    {45, 23, 9},
    {3, -4, -134},
    {67, 53, 32},
    {0, 1, 0}
};

// test.GetLength(n) will give the length at nth dimension.
// test.Length will give total length. (4*3)

var colLength = test.GetLength(1);

for (int i = 0; i < test.Length - 1; i++)
{
    for (int j = i + 1; j < test.Length; j++)
    {
        int row1, col1; // for first item
        int row2, col2; // next item

        Get2DIndex(i, colLength, out row1, out col1); // calculate indexes for first item

        Get2DIndex(j, colLength, out row2, out col2); // calculate indexes for next item

        if (test[col2, row2] < test[col1, row1]) // simple swap
        {
            var temp = test[col2, row2];
            test[col2, row2] = test[col1, row1];
            test[col1, row1] = temp;
        }
    }
}

Print the results:

for (int i = 0; i < test.GetLength(0); i++)
{
    for (int j = 0; j < test.GetLength(1); j++)
    {
        Console.Write("{0}\t", test[i, j]);
    }
    Console.WriteLine();
}