how to delete one column and row from jagged array in c#

Question

I have following jagged array of "dists"

int[][] dists = new int[][]
{
    new int[]{0,2,3,5,2},
    new int[]{2,0,1,3,5},
    new int[]{3,1,0,4,4},
    new int[]{5,3,4,0,2},
    new int[]{2,5,4,2,0}
};

now I want to create another jagged array named as finalDists when I remove the 3rd row and 3rd column from original array of dists. I mean I want finally have following jagged array:

int[][] finalDists = new int[][]
{
    new int[]{0,2,5,2},
    new int[]{2,0,3,5},
    new int[]{5,3,0,2},
    new int[]{2,5,2,0}
};

I am confused how to handle this issue, before all thanks for your help

Consider using existing solutions for mathematics and matrices. No need to reinvent the wheel, assuming that is a matrix with matrix logic applied to it. — YoryeNathan
– YoryeNathan, Commented Apr 19, 2015 at 10:29

ASh · Accepted Answer · 2015-04-19 10:46:01Z

8

int[][] finalDists = dists.Where((arr, i)=>i!=2) //skip row#3
                          .Select(arr=>arr.Where((item,i)=>i!=2) //skip col#3
                                          .ToArray())
                          .ToArray();

edited Apr 19, 2015 at 10:46

answered Apr 19, 2015 at 10:26

ASh

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3 Comments

Hesam E Over a year ago

I had mistake, now your proposed solution works. :) Many thanks for your intimidate response.

Hesam E Over a year ago

I am new at Stackoverflow, I don't know how to accept and vote :)

Hesam E Over a year ago

Can you help for this probelm: [link] (stackoverflow.com/questions/29875959/…) thanks

xanatos · Accepted Answer · 2015-04-19 10:56:32Z

Not very optimized but:

public static T[] RemoveRow<T>(T[] array, int row)
{
    T[] array2 = new T[array.Length - 1];

    Array.Copy(array, 0, array2, 0, row);
    Array.Copy(array, row + 1, array2, row, array2.Length - row);

    return array2;
}

public static T[][] RemoveColumn<T>(T[][] array, int column)
{
    T[][] array2 = new T[array.Length][];

    for (int i = 0; i < array.Length; i++)
    {
        array2[i] = RemoveRow(array[i], column);
    }

    return array2;
}

and

int[][] dists = new int[][]
{
    new int[]{0,2,3,5,2},
    new int[]{2,0,1,3,5},
    new int[]{3,1,0,4,4},
    new int[]{5,3,4,0,2},
    new int[]{2,5,4,2,0}
};

int[][] dists2 = RemoveColumn(RemoveRow(dists, 2), 2);

Note that you want to remove the third row and the third column, but their index is 2, because .NET arrays are 0-based indexed!

Lawrence Lewis · Accepted Answer · 2025-03-03 18:10:49Z

I tested all of the solutions on stack overflow on 3/3/2025 and this one was fastest on my test case.

static T[][] removeRowsAndColumns<T>(T[][] inputArray, List<int> rowsToRemove, List<int> columnsToRemove)
{
    T[][] removedRowsAndColumnsArray = new T[inputArray.Length - rowsToRemove.Count][];
    int currentRowIndex = 0;
    for (int i = 0; i < inputArray.Length; i++)
    {
        if (!rowsToRemove.Contains(i))
        {
            //removedRowsArray[currentRowIndex] = inputArray[i];
            removedRowsAndColumnsArray[currentRowIndex] = new T[inputArray[i].Length - columnsToRemove.Count];
            int currentColIndex = 0;
            for (int j = 0; j < inputArray[i].Length; j++)
            {
                if (!columnsToRemove.Contains(j))
                {
                    removedRowsAndColumnsArray[currentRowIndex][currentColIndex] = inputArray[i][j];
                    currentColIndex++;
                }
            }
            currentRowIndex++;
        }
    }
    return removedRowsAndColumnsArray;
}

Here is an example

int[][] thingToTest =
{
    new int[ ] { 10,  20,  30, 5},
    new int[ ] { 11,  22,   3, 4},
    new int[ ] { 88,  99,   1, 2},
    new int[ ] {111, 222, 333, 6}
};
List<int> rowsToRemove    = new List<int>() {2};
List<int> columnsToRemove = new List<int>() {2};


int[][] arrayWithRemovedColumnsAndRows = removeRowsAndColumns<int>(thingToTest, rowsToRemove, columnsToRemove);

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