Advent of Code 2023, December 4

AdventOfCode2023.12.04.fsx

#time "on"

open System
open System.IO
open System.Collections.Generic

let parseCards (str: string) =
    str.Trim().Split(' ') |> Seq.filter(not << String.IsNullOrWhiteSpace) |> Seq.map Int32.Parse |> Seq.toArray

let parseLine (str: string) =
    let items = str.Split([|':'; '|'|])
    parseCards items[1], parseCards items[2]

let input =
    File.ReadAllLines(__SOURCE_DIRECTORY__ + "/../data/input04.txt")
    |> Seq.toArray
    |> Array.map parseLine

// Part One
input
|> Array.map (fun (winning, cards) -> 
    cards |> Array.fold (fun acc card -> if Array.contains card winning then (if acc = 0 then 1 else acc * 2) else acc) 0)
|> Array.sum

// Part Two
let acc = Dictionary<int, (int * int)>()
input
|> Array.iteri (fun ndx (winning, cards) -> 
    acc.Add(ndx + 1, (cards |> Array.filter (fun card -> Array.contains card winning) |> Array.length, 1)))

for ndx in acc.Keys do
    for i in [1..fst acc[ndx]] do
        if acc.ContainsKey (ndx + i) then
            let x, y = acc[ndx + i]
            acc[ndx + i] <- (x, y + (snd acc[ndx]))

acc |> Seq.sumBy(fun kv -> snd kv.Value)