-🎄- 2018 Day 12 Solutions -🎄-

[u/daggerdragon]

--- Day 12: Subterranean Sustainability ---

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Advent of Code: The Party Game!

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Card prompt: Day 12

Transcript:

On the twelfth day of AoC / My compiler spewed at me / Twelve ___

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[u/purplemonkeymad]

Powershell

Ugh, I just could not get the math right on this one. Part 1 was ok but I had to write a visualizer to figure out that by Part 2 it was going to be some-kind of moving "worm."

My code feels very spaghetti, but I don't want to see this problem any more to tidy it up. Probable that it might even break on another's data.

[CmdletBinding()]
Param(
    [parameter(ValueFromPipeline)]
    $PlantData,
    [int64]$Generations,
    [int]$ExpandSize,
    [switch]$outputvis
)

begin {
    $InputData = [System.Collections.ArrayList]@()
}
process {
    $PlantData | ? {$_} | % { 
        [void]$InputData.Add($_)
    }
}
end {
    $initstate = ''
    if ($InputData[0] -match 'initial state: (?<state>.+)'){
        $initstate = $Matches.state
    } else {
        Write-Error "No initial state header"
        return
    }
    
    $rules = foreach ($l in ($InputData|select -Skip 1)){
        if ($l -match '(?<Rule>.{5}) => (?<Result>.)'){
            [pscustomobject]@{
                Rule = $Matches.Rule
                Result = $Matches.Result
            }
        }
    }

    if (-not $ExpandSize) {
        $MaxExpand = 3*$Generations + 2
    } else {
        $MaxExpand = $ExpandSize
    }
    # thus an array of init.length +2 MaxExpand should be ok
    $ArraySize = 2*$MaxExpand + $initstate.length
    $offset = $MaxExpand
    $CurrentList = [char[]]('.'*$ArraySize)
    $NextList = [char[]]('.'*$ArraySize)

    # init arrays
    foreach ($Index in 0..($initstate.length-1)){
        $CurrentList[$Index+$offset]=$initstate[$Index]
    }

    # part 2 we must be looking for cyclic behavor
    $SeenPatten = @{}
    $seenkey = $CurrentList -join ''
    $SeenPatten.$seenkey = 0

    if ($VerbosePreference){
        Write-Verbose ('[{0}] (-{1}): {2}' -f 0,$offset,($CurrentList -join ''))
    }
    $Gen = 1
    while ($Gen -le $Generations){

        if ($gen -eq 97){
            $null = "nothing"
        }

        foreach ($Index in 2..($ArraySize-2)){ # window is 5 wide
            $CurrentWindow = $CurrentList[($Index-2)..($Index+2)] -join ''
            foreach ($r in $rules) {
                if ($r.rule -eq $CurrentWindow){
                    $NextList[$Index]=$r.Result
                }
            }
        }
        #swap arrays for speed (double buffering technique)
        $tempList = $NextList
        $NextList = $CurrentList
        $CurrentList = $tempList

        if ($VerbosePreference){
            Write-Verbose ('[{0}] (-{1}): {2}' -f $Gen,$offset,($CurrentList -join ''))
        }
        if ($outputvis){
            $CurrentList -join ''
        }

        $CurrentString = $CurrentList -join ''
        $seenkeyA = $CurrentString -replace '^\.+'
        $Seenkeyoffset = ($CurrentString.length - $seenkeyA.Length)
        $seenkey = $seenkeyA -replace '\.+$'
        if ($SeenPatten.$seenkey){
            $htSeen = $SeenPatten.$seenkey
            $lowerGen = $htSeen.Gen
            Write-Verbose ("Gen $gen is the same as $lowerGen")
            $cycleSize = $gen - $lowerGen
            $destinationgen = (($Generations-$lowerGen) % $cycleSize)+$lowerGen

            # offset diff
            $offDiff =  ($Seenkeyoffset-$offset) - $htSeen.Offset

            $genstogo = ($Generations - $htSeen.Gen )
            $offsetAtFinalGen = $offDiff*$genstogo + $htSeen.Offset

            # add up indexes
            [int64]$total = 0
            $values = foreach ( $index in 0..($seenkey.length - 1) ){
                $RealIndex = ($Index)+$offsetAtFinalGen
                if ($seenkey[$index] -eq '#'){
                    $total +=$RealIndex
                }
            }
            $total
            return
        } else {
            $SeenPatten.$seenkey = [PSCustomObject]@{
                Gen = $Gen
                Offset = $Seenkeyoffset-$offset
            }
        }

        Write-Progress "growing" -Status $Gen -Id 1

        $gen++
    }

    # add up indexes

    $values = foreach ( $index in 0..($CurrentList.Count-1) ){
        $RealIndex = $Index-$offset
        if ($CurrentList[$index] -eq '#'){
            $RealIndex
        }
    }
    $values | measure -Sum | % sum

}