AdventOfCode_Day3.fsx

open System
open System.IO

let getHouses directions = 
    directions
    |> Seq.map (fun x ->
        match x with
        | '>' -> (fun (x: int, y: int) -> (x + 1, y))
        | '<' -> (fun (x: int, y: int) -> (x - 1, y))
        | '^' -> (fun (x: int, y: int) -> (x, y + 1))
        | 'v' -> (fun (x: int, y: int) -> (x, y - 1))
        | _   -> (fun (x: int, y: int) -> (x, y))
    )
    |> Seq.fold (fun l move -> move(l.Head) :: l) [(0, 0)]
    
let splitList list = Array.foldBack (fun x (l,r) -> x::r, l) list ([],[])

let input = File.ReadAllText("AdventOfCode_Day3_input.txt").ToCharArray()

let part1 =
    input
    |> getHouses
    |> Seq.distinct
    |> Seq.length

let part2 = 
    input
    |> splitList
    |> (fun t -> 
        let l, r = t
        [ l; r ] 
       )
    |> Seq.map getHouses
    |> Seq.concat
    |> Seq.distinct
    |> Seq.length