IsUnival.fs

// /*
// Unival Tree


// #1: 5
//  0
// |  \
// 0   1   
// | \
// 1  0
// |
// 1
// |\
// 1 1


// #2: 2
// 0
// | \
// 0  0
//    |
//    1

// */

type Tree<'a> =
    | Node of 'a * Tree<'a> list
    | Leaf of 'a


let isUnival tree =

    let rec inner tree = 

        match tree with
        | Leaf value -> Result.Ok (1,value)
        | Node (value,children) ->

            let allUnival,count =
                children
                |> List.map inner
                |> List.fold (fun (check,total) x -> 
                    match x with
                    | Ok (c,v) when v = value -> check, total + c
                    | Ok (c,v) -> false, total + c
                    | Error c -> false, total + c  
                ) (true,0)

            if allUnival 
            then Ok (count + 1, value)
            else Result.Error count

    inner tree |> function
        | Ok (c,v) -> c
        | Error c -> c


Leaf 0
|> isUnival |> printf "%i"

Node (0, [Leaf 0])
|> isUnival |> printf "%i"

Node (0, [Leaf 0; Leaf 1])
|> isUnival |> printf "%i"

Node (0, [
    Node (0,[Leaf 0; Leaf 0])
    Leaf 1
    ])
|> isUnival |> printf "%i"


Node (0, [
    Node (0,[Leaf 0; Leaf 0])
    Leaf 0
    ])
|> isUnival |> printf "%i"