URL

https://leetcode.com/problems/largest-3-same-digit-number-in-string/description/?envType=daily-question&envId=2023-12-04

Code

https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/challenge/202312/largest_3_same_digit_number_in_string/main.fsx

open System

let largestGoodInteger (num: string) : string =
    let rec largestGoodInteger' (cs: char list) acc =
        match cs with
        | [] -> acc
        | a :: b :: c :: t when a = b && b = c ->
            let s = [ a; a; a ] |> String.Concat

            if s > acc then
                largestGoodInteger' t s
            else
                largestGoodInteger' t acc
        | _ :: t -> largestGoodInteger' t acc

    largestGoodInteger' (Seq.toList num) ""