Advent of Code 2023, December 1

AdventOfCode2023.12.01.fsx

open System
open System.IO

let input =
    File.ReadAllLines(__SOURCE_DIRECTORY__ + "/../data/input01.txt")
    |> Seq.toList

let findNum1 x =
    if x >= '0' && x <= '9' then Some (int (x-'0')) else None

let digits = ["one"; "two"; "three"; "four"; "five"; "six"; "seven"; "eight"; "nine"]

let rec findNum2 (str: string) (digits: string list) =
    printfn "%s" str
    if str[0] >= '0' && str[0] <= '9' then
        int (str[0]-'0')
    else
        match digits |> List.tryFindIndex (fun x -> str.StartsWith x) with
        | Some n -> n + 1
        | None -> findNum2 (str.Substring(1)) digits

let reverseString (str: string) =
    str |> Seq.toArray |> Array.rev |> String

// Part One
input
|> List.map (fun str -> str |> Seq.toList)
|> List.map (fun chars -> chars |> List.pick findNum1, chars |> List.rev |> List.pick findNum1)
|> List.map (fun (x,y) -> x * 10 + y)
|> List.sum

// Part Two
input
|> List.map (fun str -> findNum2 str digits, findNum2 (reverseString str) (digits |> List.map reverseString))
|> List.map (fun (x,y) -> x * 10 + y)
|> List.sum