Question

I feel like I keep bugging everyone about this, so sorry for ‘this guy again’.

My four in a row game now works, up until the point where it needs to be checked for a four in a row. The X and O get added to columns like a charm and the grid is showing correct. The point now is that I want to check for a four in a row in my multidimensional array, but using if statements doesn’t really seem the way to go to me as I would have to write this:

if ($CreateBoard[1,0] -and $CreateBoard[1,1] -and $CreateBoard[1,2] -and $CreateBoard[1,3] -eq "X") {Write-host "Exit script!"}
if ($CreateBoard[1,1] -and $CreateBoard[1,2] -and $CreateBoard[1,3] -and $CreateBoard[1,4] -eq "X") {Write-host "Exit script!"}
if ($CreateBoard[1,2] -and $CreateBoard[1,3] -and $CreateBoard[1,4] -and $CreateBoard[1,5] -eq "X") {Write-host "Exit script!"} 
if ($CreateBoard[1,3] -and $CreateBoard[1,4] -and $CreateBoard[1,5] -and $CreateBoard[1,6] -eq "X") {Write-host "Exit script!"} 
if ($CreateBoard[1,4] -and $CreateBoard[1,5] -and $CreateBoard[1,6] -and $CreateBoard[1,7] -eq "X") {Write-host "Exit script!"} 
if ($CreateBoard[1,5] -and $CreateBoard[1,6] -and $CreateBoard[1,7] -and $CreateBoard[1,8] -eq "X") {Write-host "Exit script!"} 
if ($CreateBoard[1,6] -and $CreateBoard[1,7] -and $CreateBoard[1,8] -and $CreateBoard[1,9] -eq "X") {Write-host "Exit script!"}
if ($CreateBoard[1,7] -and $CreateBoard[1,8] -and $CreateBoard[1,9] -and $CreateBoard[1,10] -eq "X") {Write-host "Exit script!"} 

for every single column, then row, and then go diagonal. Question now is: Is there a fast way to go through my 10×10 grid (I guess using Foreach-Object of for loops?), and if yes, could you provide a basic example? (I am trying to find 4 times the string “X” OR “O” in a row if that matters)

Thanks

Answer 1

This is more of an algorithm question than a PowerShell question. 🙂 That said, one simple approach would be something like this:

function FindFourInARow($brd, $startRow, $startCol)
{
    $numRows = $brd.GetLength(0);
    $numCols = $brd.GetLength(0);

    #search horizontal
    $found = 0;
    $cnt  = 0;
    for ($col = $startCol; $col -lt $numCols -and $cnt -lt 4; $col++, $cnt++)
    {
        if ($brd[$startRow, $col] -eq 'X')
        {
            $found += 1
            if ($found -eq 4) { return $true }
        }
    }

    #search vertical
    $found = 0;
    $cnt = 0;
    for ($row = $startRow; $row -lt $numRows -and $cnt -lt 4; $row++, $cnt++)
    {
        if ($brd[$row, $startCol] -eq 'X')
        {
            $found += 1
            if ($found -eq 4) { return $true }
        }
    }

    #search diag forwards
    $found = 0;
    $row = $startRow
    $col = $startCol
    $cnt = 0;
    for (;$row -lt $numRows -and $col -lt $numCols -and $cnt -lt 4; 
          $row++, $col++, $cnt++)
    {
        if ($brd[$row, $col] -eq 'X')
        {
            $found += 1
            if ($found -eq 4) { return $true }
        }
    }

    return $false
}

# TODO: implement search diag backwards

$brd = New-Object 'char[,]' 10,10
$brd[2,2] = $brd[3,3] = $brd[4,4] = $brd[5,5] = 'X'

$numRows = 10
$numCols = 10
for ($r = 0; $r -lt ($numRows - 3); $r++)
{
    for ($c = 0; $c -lt ($numCols - 3); $c++)
    {
        if (FindFourInARow $brd $r $c)
        {
            "Found four in a row at $r,$c"
            $r = $numRows
            break;
        }
    }
}

I’ve just typed this directly into SO. It’s likely got some errors but it should give you the basic gist of things.