day4.ps1

 function Import-PuzzleInput {    
        param (    
            $Path    
        )    
        $puzzleInput = Get-Content $Path     
        $puzzleInput -replace '.*:' | ForEach-Object {    
         
            $scratchCardNumbers, $null, $numbersYouHave = $_ -replace ' +', ' ' -split '( \| )'    
            $scratchCardNumbers = $scratchCardNumbers -split ' '    
            $numbersYouHave = $numbersYouHave -split ' '    
            $winningNumbers = Compare-Object $scratchCardNumbers $numbersYouHave -IncludeEqual -ExcludeDifferent    
        
            [PSCustomObject]@{    
                ScratchCardNumbers = $scratchCardNumbers    
                NumbersYouHave     = $numbersYouHave    
                NumberOfMatches    = $winningNumbers.Length    
                InstanceCount      = 1    
            }    
        }    
    }    
        
    function Get-WinningPoints {    
        param (    
        
            [Parameter(ValueFromPipeline)]    
            $InputObject    
        )    
        Begin {    
            $sum = 0    
        }    
        Process {    
            foreach ($item in $InputObject) {    
            
                if ($winningNumbers) {    
                    $points = [math]::Pow(2, $item.NumberOfMatches - 1)    
                    $sum += $points    
                }    
            }    
        }    
        End {    
            Write-Output $sum    
        }    
    }    
        
    function Get-CardCopies {    
        param (    
        
            $InputObject    
        )    
        
        $scratchCards = $InputObject    
        for ($i = 0; $i -lt $scratchCards.Count; $i++) {    
        
            if ($scratchCards[$i].NumberOfMatches -eq 0) {    
                continue    
            }    
            $copyStart = $i + 1    
            $copyEnd = $i + $scratchCards[$i].NumberOfMatches    
            $copyRange = $copyStart .. $copyEnd | Where-Object { $_ -lt $scratchCards.Length }    
        
            foreach ($copyIndex in $copyRange) {    
                $cardToCopy = $scratchCards[$copyIndex]    
                $cardToCopy.InstanceCount += $scratchCards[$i].InstanceCount    
            }    
        }    
        Write-Output $scratchCards    
    }    
        
    $puzzleInput = Import-PuzzleInput $PSScriptRoot/input.txt
        
        
    # Part 1    
    $puzzleInput | Get-WinningPoints    
        
    # Part 2     
    Get-CardCopies $puzzleInput | Measure-Object -Property InstanceCount -Sum