create checkerboard with alternating patterns

[Plotweaver]

I'm creating a video game that uses an 8 by 8 grid. I need half of the 64 cells to be black and half white. I'm using conditional formatting to highlight the cells white or black. I've got a randomizer to randomly make the cells either black or white. But, I can't figure out a way so that - no matter the pattern - half are white and half are black. Can you help me devise a formula that will do this? Thanks in advance.

 

[Paul Ked]

Hi and welcome to the forum.

This will produce a 32 random black squares in the range B2:I9:

Sub FillGrid()[INDENT]Randomize[/INDENT]
[INDENT]Dim rw as Long, cl as Long, i as Long
i = 1
Do[/INDENT]
[INDENT=2]rw = Int((8 - 1 + 1) * Rnd + 1) + 1
cl = Int((8 - 1 + 1) * Rnd + 1) + 1[/INDENT]
[INDENT=2]If Cells(rw, cl).Interior.Color <> RGB (0, 0, 0) Then[/INDENT]
[INDENT=3]Cells(rw, cl).Interior.Color = RGB (0, 0, 0)
i = i + 1[/INDENT]
[INDENT=2]End If[/INDENT]
[INDENT]Loop Until i = 33[/INDENT]
End Sub[INDENT]
[/INDENT]
[INDENT]
[/INDENT]

To clear the grid:

Sub ClearGrid()[INDENT]Range("B2:I9").Interior.Color = xlNone[/INDENT]
End Sub

 

[Paul Ked]

Sub FillGrid()
Randomize
Dim rw as Long, cl as Long, i as Long
i = 1
Do
rw = Int((8 - 1 + 1) * Rnd + 1) + 1
cl = Int((8 - 1 + 1) * Rnd + 1) + 1
If Cells(rw, cl).Interior.Color <> RGB (0, 0, 0) Then
Cells(rw, cl).Interior.Color = RGB (0, 0, 0)
i = i + 1
End If
Loop Until i = 33
End Sub

Sub ClearGrid()
Range("B2:I9").Interior.Color = xlNone
End Sub

Small code boxes, which I couldn't change, for some reason!

 

[Paul Ked]

And now no indents! Hey Ho!

The code will work!

 

[Paul Ked]

Edit:

To stop the program crashing I forgot to put the call to clear the grid 1st!

Sub FillGrid()
    ClearGrid
    Randomize
    Dim rw As Long, cl As Long, i As Long
    i = 1
    Do
        rw = Int((8 - 1 + 1) * Rnd + 1) + 1
        cl = Int((8 - 1 + 1) * Rnd + 1) + 1
        If Cells(rw, cl).Interior.Color <> RGB(0, 0, 0) Then
            Cells(rw, cl).Interior.Color = RGB(0, 0, 0)
            i = i + 1
        End If
    Loop Until i = 33
End Sub


Sub ClearGrid()
    Range("B2:I9").Interior.Color = xlNone
End Sub

 

[Plotweaver]

Thanks. I'll try it and see if it accomplishes what I have in mind.

My ideal method would be to randomly select one of the 64 cells. Then move it to a new location. Meanwhile the cell in the new location is being moved to yet a third location... and so on. Just make sure the randomly selected cell has not been move previously. A literal 'shuffle' of cells.

 

[mikerickson]

You could use conditional formatting with the formula =ISEVEN(ROW()+COLUMN())

 

[Plotweaver]

Paul:
I keep getting a compile error message: Ambiguous name detected: FillGrid

 

[Rick Rothstein]

Paul:
I keep getting a compile error message: Ambiguous name detected: FillGrid

That means you have two or more procedures with the same name. Find the one you want to use and delete all of the others.

 

[Rick Rothstein]

You could use conditional formatting with the formula =ISEVEN(ROW()+COLUMN())

I know what the thread title says, but if you read Message #1 carefully, I think you will see the OP is not looking for a regular checkerboard pattern, rather, he seems to be asking for half of a the squares on a checkerboard to be randomly selected and colored (his problem appears to be limiting the randomizing selection to 32 non-repeating squares).