Advent Of Code Day 5 2020

AOC_Day5.ps1

#-------
# PART 1
#-------
# input file
$plane=Get-Content "/Users/{username}/Downloads/AdventOfCode_Day5.txt"

Function Get-Seat {
    [cmdletbinding()]
    param(
        [Parameter(Mandatory)]
        [string] $Seat
    )

    $PlaneRow = $Seat.substring(0,7)
    $RowCharArray = $PlaneRow.ToCharArray()

    If ($RowCharArray[0] -eq 'F') {
        $Pool=0..63
    }
    If ($RowCharArray[0] -eq 'B') {
        $Pool=64..127
    }
    
    # Get the seat row
    Foreach ($char in (1..6)){
        If ($RowCharArray[$char] -eq 'F') {
            $Pool=[Math]::Ceiling($Pool[0])..[Math]::Floor(($Pool[-1]-$Pool[0]) /2 + $Pool[0] )
        }
        If ($RowCharArray[$char] -eq 'B') {
            $Pool=[Math]::Ceiling(($Pool[-1]-$Pool[0]) /2 + $Pool[0])..[Math]::Floor($Pool[-1] )
        }
    }

    # Get the seat column
    $Column=0..7
    $PlaneColumn = $Seat.substring(7,3)
    $ColumnCharArray = $PlaneColumn.ToCharArray()

    Foreach ($char in (0..2)){
        If ($ColumnCharArray[$char] -eq 'L') {
            $Column=[Math]::Ceiling($Column[0])..[Math]::Floor(($Column[-1]-$Column[0]) /2 + $Column[0] )
            #write-host "Set column $Column" -fore green
        }
        If ($ColumnCharArray[$char] -eq 'R') {
            $Column=[Math]::Ceiling(($Column[-1]-$Column[0]) /2 + $Column[0])..[Math]::Floor($Column[-1] )
            #write-host "Set column $Column" -fore cyan
        }
    }

    $Output = [PSCustomObject]@{
        Seat   = $Seat
        Pool   = $Pool[0]
        Column = $Column[0]
        SeatID = (($Pool[0] * 8) + $Column[0])
    }
    Return $Output
}

$All = Foreach ($row in $plane){
    Get-Seat -Seat $row
}

$All | Sort-Object SeatID | Select-Object -Last 1

#-------
# PART 2
#-------

$All.SeatID | Sort-Object | ForEach-Object {
    $LastID = $ThisID
    $ThisID = $_
    
    If ($ThisID - $LastID -ne 1 -and $LastID){
        Write-Host "$($ThisID -1) is not present" -fore Green
    }
}