Advent of Code 2022 - Day 3

open System.IO
open System

type Input() =

    let mapToPriority (c: char) : int =
        let cVal = (int) c

        if cVal <= (int) 'Z' then
            cVal - (int) 'A' + 1 + 26
        else
            cVal - (int) 'a' + 1

    let computePart1 (line: string) : int =
        let sorted =
            line
            |> Seq.toArray
            |> Array.splitInto 2
            |> Array.map Array.distinct
            |> Array.sortBy (fun x -> x.Length)

        sorted[0]
        |> Array.filter (fun x -> Array.contains x sorted[1])
        |> Array.fold (fun acc key -> acc + (mapToPriority (key))) 0

    let computePart2 (l1: string, l2: string, l3: string) =
        let sorted =
            [| l1; l2; l3 |]
            |> Array.map (Seq.distinct >> Seq.toArray)
            |> Array.sortBy (fun x -> x.Length)

        sorted[0]
        |> Array.find (fun c -> (Array.contains c sorted[1]) && (Array.contains c sorted[2]))
        |> mapToPriority

    member _.Compute(part: int) =
        use stream = new StreamReader "./input.txt"

        let mutable sum = 0
        let mutable endOfFile = false

        while (not endOfFile) do
            let line = stream.ReadLine()

            if (line = null) then
                endOfFile <- true
            else if (part = 1) then
                sum <- sum + computePart1 line
            else
                sum <- sum + computePart2 (line, stream.ReadLine(), stream.ReadLine())

        sum

let input = Input()
let part = (Environment.GetCommandLineArgs()[1]) |> int

printfn "%d" (input.Compute(part))