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|
module Day18
open System.IO
open FParsec
open Common
let parsePos =
Util.parse (
tuple3 (pint32 .>> pchar ',') (pint32 .>> pchar ',') pint32
|>> Vec3
)
let fullSurface cubes =
cubes
|> Seq.collect Vec3.neighbours6
|> Seq.filter (Util.notIn cubes)
|> Seq.length
let externalSurface cubes =
let hasLava pos = Set.contains pos cubes
let minBound = Seq.reduce (Vec3.combine min) cubes - Vec3.ones
let maxBound = Seq.reduce (Vec3.combine max) cubes + Vec3.ones
let neighbours pos =
match hasLava pos with
| true -> []
| false -> List.filter (Vec3.boundedBy minBound maxBound) (Vec3.neighbours6 pos)
let rec dfs visited count =
function
| pos :: stackTail ->
let count' = count + if hasLava pos then 1 else 0
match Set.contains pos visited with
| true -> dfs visited count' stackTail
| false -> dfs (Set.add pos visited) count' (neighbours pos @ stackTail)
| [] -> count
dfs Set.empty 0 [ minBound ]
let solution surface =
Seq.map parsePos >> Set.ofSeq >> surface
let test = File.ReadLines("test.txt")
assert (solution fullSurface test = 64)
assert (solution externalSurface test = 2540)
let input = File.ReadLines("input.txt")
printfn "%d" <| solution fullSurface input
printfn "%d" <| solution externalSurface input
|
