URL

Count Number of Homogenous Substrings - LeetCode

Code

https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/problems/1759/main.fsx

let countHomogenous (s: string) : int =
    let modulo = 1_000_000_007

    let rec countHomonogenous' cs prev count acc =
        match cs with
        | [] -> acc
        | h :: t ->
            if h = prev then
                let count' = count + 1
                countHomonogenous' t h count' ((acc + count') % modulo)
            else
                countHomonogenous' t h 1 ((acc + 1) % modulo)

    let cs = Seq.toList s
    countHomonogenous' (List.tail cs) (List.head cs) 1 1