Sudoku.ps1

$global:board = @(
    @(0,0,0, 0,3,0, 0,0,0),
    @(0,0,1, 0,7,6, 9,4,0),
    @(0,8,0, 9,0,0, 0,0,0),

    @(0,4,0, 0,0,1, 0,0,0),
    @(0,2,8, 0,9,0, 0,0,0),
    @(0,0,0, 0,0,0, 1,6,0),

    @(7,0,0, 8,0,0, 0,0,0),
    @(0,0,0, 0,0,0, 4,0,2),
    @(0,9,0, 0,1,0, 3,0,0)
)

function print_board {
    foreach ($i in 0..8) {
        if ($i % 3 -eq 0 -and $i -ne 0) {
            Write-Host "- - - - - - - - - - -"
        }

        foreach ($j in 0..8) {
            if ($j % 3 -eq 0 -and $j -ne 0) {
                Write-Host "| " -NoNewline
            }

            if ($j -eq 8) {
                Write-Host $global:board[$i][$j]
            }
            else {
                Write-Host ([string]$global:board[$i][$j] + " ") -NoNewline
            }
        }
    }
}

function find_empty {
    foreach ($i in 0..8) {
        foreach ($j in 0..8) {
            if ($global:board[$i][$j] -eq 0) {
                return $i, $j  # row, col
            }
        }
    }
    return $null
}

function valid($num, $pos) {
    # Check row
    foreach ($i in 0..8) {
        if ($global:board[$pos[0]][$i] -eq $num -and $pos[1] -ne $i) {
            return $False
        }
    }

    # Check column
    foreach ($i in 0..8) {
        if ($global:board[$i][$pos[1]] -eq $num -and $pos[0] -ne $i) {
            return $False
        }
    } 

    # Check box
    $box_x = [math]::floor($pos[1] / 3)
    $box_y = [math]::floor($pos[0] / 3)

    foreach ($i in ($box_y*3)..($box_y*3 + 2)) {
        foreach ($j in ($box_x * 3)..($box_x*3 + 2)) {
            if ($global:board[$i][$j] -eq $num -and @($i,$j) -ne $pos) {
                return $False
            }
        }
    }

    return $True
}

function solve {
    $find = find_empty
    if (-not $find) {
        return $True
    }
    else {
        $row, $col = $find
        #Write-Progress -Activity "Solving..." -CurrentOperation "Row: $($row+1), Col: $($col+1)" -PercentComplete ([math]::round($row*$col/64*100))
        #[Console]::Write("`rSolving... Row: $($row+1), Col: $($col+1)")
    }

    foreach ($i in 1..9) {
        if (valid $i @($row, $col)) {
            $global:board[$row][$col] = $i
            #print_board

            if (solve) {
                return $True
            }

            $global:board[$row][$col] = 0
        }
    }

    return $False
}

print_board
$time = Measure-Command {solve}
Write-Host ""
Write-Host "Seconds to Solve: $($time.TotalSeconds)"
Write-Host ""
Write-Host "_____________________"
print_board