Removing items in Jagged array using index

Question

I want to remove items of a Jagged array using indizes.

int[] toRemove; (e.g, {0, 1})

int[][] MainArray (e.g. { [0] {...}, [1] {...}, [2] {...}}

Expected result

int[][] result (e.g. {[2] {...}}

From the MainArray how to remove the items which having indexes from the toRemove list?

Is there an efficient way using LINQ?

Linq is a query facility, it doesn't directly remove items (though you can query a sub-set and assign it back to the original) — James Michael Hare
– James Michael Hare, Commented Mar 22, 2012 at 13:59
You cannot remove from an array, you understand you will get a new array? And does that have to be an array again? — Henk Holterman
– Henk Holterman, Commented Mar 22, 2012 at 14:13

Tim Schmelter · Accepted Answer · 2013-09-09 07:29:32Z

3

Hopefully this gives the expected result:

var notInToRemove = MainArray
    .Where((arr ,index) => !toRemove.Contains(index)).ToArray();

edited Sep 9, 2013 at 7:29

answered Mar 22, 2012 at 14:08

Tim Schmelter

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3 Comments

gprasant Over a year ago

Now I know why Where method has an overload with the int Index parmeter ;-)

Suresh Over a year ago

Thanks Tim. Great support. Works as expected and as I needed. LINQ is so elegant, but hard learning :-(. By the way, I also studied in Aachen. Nice to know you.

Tim Schmelter Over a year ago

@Suresh: ... and i'm still living and working here, i'm happy to hear that it works :) LINQ is hard at the beginning because it compresses complexity and you often need to think laterally. But the result is almost always more comprehensible. Find the way to the corect result in mind and then begin to write the query, not vice-versa.

gprasant · Accepted Answer · 2012-03-22 14:14:11Z

0

You could use the ElementAt method instead of the Remove method if all you want is the data that is not to be there in the toRemove set.

int[] toRemove = {0,1};
int[][] mainArray = new int[3][];
mainArray[0] = new int[]{0,0,0};
mainArray[1] = new int[]{1,1,1};
mainArray[2] = new int[]{2,2,2};

var result = mainArray.ElementAt(2); // This value 2 is found as all indexes of mainArray except the values in toRemove
//(Code would look like this : 
Enumerable.Range(0, mainArray.Length).Except(toRemove);

edited Mar 22, 2012 at 14:14

answered Mar 22, 2012 at 14:09

gprasant

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