howManyEqual.erl

-module(howManyEqual).
-export([howManyEqual/3]).

rm_dup(List) ->
    lists:foldl(
        fun(Elem, Acc) ->
            case lists:member(Elem, Acc) of
                true ->
                    Acc;
                false ->
                    Acc ++ [Elem]
            end
        end, [], List
    ).

howManyEqual(X, X, X) ->
    3;

howManyEqual(A, B, C) ->
    case length(rm_dup([A, B, C])) of
        1 -> 3;
        2 -> 2;
        3 -> 0
    end.