class Solitaire:
    # ...
    def minimale(self):
        d_resultat = {}
        d_a_traiter = {self.initial.num():0}
        file_a_traiter = [self.initial]
        num_final = self.final.num()
        while num_final not in d_resultat and file_a_traiter:
            m = file_a_traiter.pop(0)
            num = m.num()
            s = d_a_traiter.pop(num)
            if num not in d_resultat:
                d_resultat[num] = s
            file_a_traiter.extend(self.strate(d_a_traiter, s+1, [m]))
        try:
            return d_resultat[num_final]
        except:
            KeyError('Motif final inatteignable')