how can I return the index of an object in a 2 dimensional array?

Question

I am working with a 2-D array of nullable booleans bool?[,]. I am trying to write a method that will cycle through its elements 1 at a time starting at the top, and for each index that is null, it will return the index.

Here is what I have so far:

public ITicTacToe.Point Turn(bool player, ITicTacToe.T3Board game)
{
    foreach (bool? b in grid)
    {
        if (b.HasValue == false)
        {                      
        }
        if (b.Value == null)
        {
        }


    }
    return new Point();

 }

I want to be able to set the object to true/false depending on the bool passed in. Point is just a class with an x,y.

What's a great way to write this method?

This helps a lot, thank you. I am still fairly new to C#, what is the purpose of this code? mostly I am confused about the {true,null} and {false, true} parts. bool?[,] bools = new bool?[,] { { true, null }, { false, true } }; — Cody
– Cody, Commented Oct 15, 2010 at 5:02

Kirk Woll · Accepted Answer · 2010-10-15 02:36:02Z

2

You should use a normal for loop and use the .GetLength(int) method.

public class Program
{
    public static void Main(string[] args)
    {
        bool?[,] bools = new bool?[,] { { true, null }, { false, true } };

        for (int i = 0; i < bools.GetLength(0); i++)
        {
            for (int j = 0; j < bools.GetLength(1); j++)
            {
                if (bools[i, j] == null)
                    Console.WriteLine("Index of null value: (" + i + ", " + j + ")");
            }
        }
    }
}

The parameter to .GetLength(int) is the dimension (i.e. in [x,y,z], You should pass 0 for length of dimension x, 1 for y, and 2 for z.)

answered Oct 15, 2010 at 2:36

Kirk Woll

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Comments

SamStephens · Accepted Answer · 2010-10-15 02:59:51Z

Just for fun, here's a version that uses LINQ and anonymous types. The magic is in the SelectMany statement, that converts our nested array into an IEnumerable<> of an anonymous type that has an X and Y coordinate, and the value in the cell. I'm using the form of Select and SelectMany that provides an index to make it easy to get the X and Y.

static

 void Main(string[] args)
 {
     bool?[][] bools = new bool?[][] { 
         new bool?[] { true, null }, 
         new bool?[] { false, true } 
     };
     var nullCoordinates = bools.
         SelectMany((row, y) => 
             row.Select((cellVal, x) => new { X = x, Y = y, Val = cellVal })).
         Where(cell => cell.Val == null);
     foreach(var coord in nullCoordinates)
         Console.WriteLine("Index of null value: ({0}, {1})", coord.X, coord.Y);
     Console.ReadKey(false);
 }

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