day18_part01.fs

module day18_part01

open AdventOfCode_2016.Modules


type TileKind =
    | SAFE
    | TRAP

let parseContent (content: string) =
    content.ToCharArray()
    |> Array.map(fun c -> if c = '.' then SAFE else TRAP)

let isTrap((left, center, right): (TileKind*TileKind*TileKind)) =
    match (left, center, right) with
    | (l, c, r) when l.IsTRAP && c.IsTRAP && r.IsSAFE -> true
    | (l, c, r) when l.IsSAFE && c.IsTRAP && r.IsTRAP -> true
    | (l, c, r) when l.IsTRAP && c.IsSAFE && r.IsSAFE -> true
    | (l, c, r) when l.IsSAFE && c.IsSAFE && r.IsTRAP -> true
    | _ -> false

let nextState (floor: TileKind array) =
    let floorchecker = Array.concat[[|SAFE|]; floor; [|SAFE|]]
    floor
    |> Array.iteri(fun idx _ -> 
        floor[idx] <- if isTrap (floorchecker[idx-1+1], floorchecker[idx+1], floorchecker[idx+1+1]) then TRAP else SAFE 
    )

let printState(floor: TileKind array) =
     String.concat "" (floor |> Array.map(fun t -> if t.IsSAFE then "." else "^"))

let countSafes(floor: TileKind array) =
    floor |> Array.filter _.IsSAFE |> Array.length

let walk (floor: TileKind array) (rows: int) =
    let mutable currentRow = 1
    let mutable map : (TileKind array * int) list = []

    map <- map @ [(floor, countSafes floor)]
    
    while currentRow < rows do
        nextState floor
        map <- map @ [(floor, countSafes floor)]
        currentRow <- currentRow + 1

    map
    |> List.sumBy snd    

let execute =
    let path = "day18/day18_input.txt"
    let content = LocalHelper.GetContentFromFile path

    let floor = parseContent content
    let mapSize = 40

    walk floor mapSize