% removes a Y element form X list
remove(Y, X) ->
    remove(Y, X, []).

remove(_Y, [], Acc) ->
    lists:reverse(Acc);

remove(Y, [X|Xs], Acc) when X =/= Y->
    remove(Y, Xs, [X|Acc]);

remove(Y, [_X|Xs], Acc) ->
    remove(Y, Xs, Acc).

nub(X) ->
    nub(X, []).

nub([], Acc) ->
    lists:reverse(Acc);
nub([X|Xs], Acc) ->
    nub(remove(X, Xs), [X | Acc]).