public NoeudArbre rechercheClef(E clef, int typeRecherche) throws Exercice1Exception {
        NoeudArbre result = NIL;
        switch (typeRecherche) {
            case SEARCH_LIST:
                result = rechercheClefList(clef);
                break;
            case SEARCH_TREE:
                if (root != NIL) {
                    result = rechercheClefArbre(clef, root);
                }
                break;
            default:
                throw new Exercice1Exception("type de recherche inconnu");
        }
        return result;
    }