CODEWITHSUNDEEP
c#arrays
sojim2
sojim2

Reputation: 1307

C# how to add an array to 2d array without it being linked?

My goal is to create a 2d array or list with default values of 0

Instead of creating the entire array an element at a time, I'm looking create an array and then copy it to multiple rows in a 2d array.

I have a row: var row = new int[] {0,0,0,0};

I'm looking to add this to a 2d array: arr[i] = row;

However, when I'm making a change to one of the rows, all of the rows change, this is because it's linked I believe. How can I copy an array to a 2d array without them being linked?

The same behavior is with a IList<list<int>>() too

Problem example: So if I update arr[0] = {1,0,0,0}

all rows would have the same values.

Upvotes: 0

Views: 103

Answers (1)

Alex Seleznyov
Alex Seleznyov

Reputation: 945

Upon creation, .NET arrays are populated with default value for each member, so explicit zeroing an array of ints is redundant. As there is no example code in the question, I wrote a quick sample to illustrate the aforementioned:

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            int w = 4;
            int h = 5;
            var arr = new int[w][];
            for (int i = 0; i < w; i++)
            {
                arr[i] = new int[h];
            }

            Console.WriteLine("Initial state");
            Print(arr);

            arr[1][2] = 1;
            Console.WriteLine("After assignment");
            Print(arr);
        }

        static void Print(int[][] arr)
        {
            for (int i = 0; i < arr.GetLength(0); i++)
            {
                var arr2 = arr[i];
                for (int j = 0; j < arr2.GetLength(0); j++)
                {
                    Console.Write(arr2[j] + " ");
                }
                Console.WriteLine();
            }
        }
    }
}

and the output is this:

Initial state
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
After assignment
0 0 0 0 0
0 0 1 0 0
0 0 0 0 0
0 0 0 0 0

If this code is not similar to what you have, please add your version to the question.

Upvotes: 1

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