Day5

# Part 1
[string[]]$bothInstructions = $puzzleInput -split '\n' | Select -SkipLast 1
$startingPosition = $bothInstructions[0..7]
$moveInstructions = $bothInstructions[10..$bothInstructions.count]

# Populate stacks
$stackCollection = @{}
$columnidx = 1
1..9 | foreach {
    [int]$stack = $_
    $stackCollection.$stack = [System.Collections.Generic.List[char]]::new()
    Write-Verbose "Working stack $stack" -Verbose
    0..7 |  foreach {
        [int]$row = $_
        if (-not [string]::IsNullOrWhiteSpace($startingPosition[$row][$columnidx])) {
            ($stackCollection.$stack).Add($startingPosition[$row][$columnidx])
        }
    }
    $columnidx += 4
    ($stackCollection.$stack).Reverse()
}

# Do moves
foreach ($moveStr in $moveInstructions) {
    [int]$move,[int]$from,[int]$to = $moveStr -split 'move|from|to|\s' | Where {-not [string]::IsNullOrWhiteSpace($_)}
    1..$move | Foreach {
        [char]$moveItem = ($stackCollection.$from)[-1]
        ($stackCollection.$from).RemoveAt($stackCollection.$from.count-1)
        ($stackCollection.$to).Add($moveItem)
    }
}
(1..9 | foreach {($stackCollection.$_)[-1]}) -join ''

# Part 2
# using clean $stackCollection
foreach ($moveStr in $moveInstructions) {
    [int]$move,[int]$from,[int]$to = $moveStr -split 'move|from|to|\s' | Where {-not [string]::IsNullOrWhiteSpace($_)}
    if ($move -gt 1) {
        [char[]]$moveItems = $null
        1..$move | Foreach {
            [char]$moveItem = ($stackCollection.$from)[-1]
            ($stackCollection.$from).RemoveAt($stackCollection.$from.count-1)
            [char[]]$moveItems += $moveItem
        }
        [array]::Reverse($moveItems)
        $moveItems | Foreach {($stackCollection.$to).Add($_)}
    }
    else {
        [char]$moveItem = ($stackCollection.$from)[-1]
        ($stackCollection.$from).RemoveAt($stackCollection.$from.count-1)
        ($stackCollection.$to).Add($moveItem)
    }
}
(1..9 | foreach {($stackCollection.$_)[-1]}) -join ''