How can I delete rows and columns from 2D array in C#?

Question

How to delete a specific row and column from 2D array in C#?

int[,] array= {{1,2,3},{4,5,6},{7,8,9}};

lets say I want to delete row i and column i (skipping them) ... for nXn array not just 3x3 and store the remaining array in a new array... so the output would be:

{5,6},{8,9}

You can't "delete" items from an array, they are fixed in size. — Calum
– Calum, Commented Oct 10, 2014 at 15:39
You cannot delete item from array. but you can create a new one, which will contain all items from original array except items you want to be deleted. — Diligent Key Presser
– Diligent Key Presser, Commented Oct 10, 2014 at 15:40
Yes, I mentioned that I want to store it in a different array not the same one — WT86
– WT86, Commented Oct 10, 2014 at 15:43

brz · Accepted Answer · 2014-10-10 16:01:34Z

9

There's no built-in way to do that, you can do it yourself:

 static void Main()
        {
            int[,] array = { { 1, 2, 3 }, { 4, 5, 6 }, { 7, 8, 9 } };
            var trim = TrimArray(0, 2, array);
        }


        public static int[,] TrimArray(int rowToRemove, int columnToRemove, int[,] originalArray)
        {
            int[,] result = new int[originalArray.GetLength(0) - 1, originalArray.GetLength(1) - 1];

            for (int i = 0, j = 0; i < originalArray.GetLength(0); i++)
            {
                if (i == rowToRemove)
                    continue;

                for (int k = 0, u = 0; k < originalArray.GetLength(1); k++)
                {
                    if (k == columnToRemove)
                        continue;

                    result[j, u] = originalArray[i, k];
                    u++;
                }
                j++;
            }

            return result;
        }

edited Oct 10, 2014 at 16:01

answered Oct 10, 2014 at 15:48

brz

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1 Comment

brz Over a year ago

@WT86 You can easily extract a method out of it, see the edited answer.

Shaharyar · Accepted Answer · 2014-10-10 15:51:49Z

2

Very simple logic. Just play with the loop:

int[,] array = { { 1, 2, 3 }, { 4, 5, 6 }, { 7, 8, 9 } };
int[,] arrayskip = new int[array.GetLength(0) - 1, array.GetLength(1) - 1];

for (int i = 1; i < array.GetLength(0); i++)
{
    for (int j = 1; j < array.GetLength(1); j++)
    {
        arrayskip[i - 1, j - 1] = array[i, j];
    }
}

answered Oct 10, 2014 at 15:51

Shaharyar

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3 Comments

WT86 Over a year ago

Thank you but in your case, if i-0, I assume an exception will be thrown since the index would be -1,-1 ? and that doesn't work.

Shaharyar Over a year ago

Then the loop will not continue because length will be 0.

TAHA SULTAN TEMURI Over a year ago

look at your condition array[i, j]; on first iteration how will you get array[0,0] element of array?

Luaan · Accepted Answer · 2014-10-10 15:38:52Z

1

No, arrays don't let you do that. You could make your own data structure for that, but it's not going to be exactly simple (unlike if you only wanted to be able to remove rows, for example).

For simple operations, it would be quite enough to build a class on top of an underlying array, and handle the re-indexing to map the virtual 2D array to the physical array underneath. But it's going to get a bit tricky as you combine removals and additions, and deform the array overall.

answered Oct 10, 2014 at 15:38

Luaan

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3 Comments

Shaharyar Over a year ago

OP asked to skip some items and store it in a new array. Not actually asked for deleting an array's item.

WT86 Over a year ago

it's not like real deleting it's just skipping specific elements and store the remaining in a new array... that's it

Luaan Over a year ago

@WT86 Well, in that case, a simple for-cycle will do. So what is your question, and where's your work? :D

WT86 · Accepted Answer · 2014-10-10 16:18:12Z

0

I created this method, have a look

 public static double[,] fillNewArr(double[,] originalArr, int row, int col)
    {
        double[,] tempArray = new double[originalArr.GetLength(0) - 1, originalArr.GetLength(1) - 1];
        int newRow = 0;
        int newCol = 0;
        for (int i = 0; i < originalArr.GetLength(0); i++)
        {
            for (int j = 0; j < originalArr.GetLength(1); j++)
            {
                if(i != row && j != col)
                {
                    tempArray[newRow, newCol] = originalArr[i, j];
                    newRow++;
                    newCol++;
                }

            }

        }
        return tempArray;

    }

having some out of range, It's obvious why but I'm trying to get there...

edited Oct 10, 2014 at 16:18

answered Oct 10, 2014 at 16:01

WT86

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4 Comments

brz Over a year ago

You'll get an IndexOutOfRangeException.

WT86 Over a year ago

yes you are right. I'm decreasing the array length by 1 and then adding the element I want in a non defined index!

WT86 Over a year ago

@brz I modified it but still out of range. I have to place newRow++ in a better place..

brz Over a year ago

Use my answer, I made it into a method.

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