LeetCode 1539. Kth Missing Positive Number in F#

URL

https://leetcode.com/problems/kth-missing-positive-number/description/

Code

https://github.com/syohex/dotnet-study/blob/master/fsharp/leetcode/problems/1539/main.fsx

let findKthPositive (arr: int list) (k: int) =
    let rec findKthPositive' i missing s k =
        if Set.contains i s then
            findKthPositive' (i + 1) missing s k
        else
            let missing' = missing + 1

            if missing' = k then
                i
            else
                findKthPositive' (i + 1) missing' s k

    let s = Set.ofList arr
    findKthPositive' 1 0 s k