class ListaElem:

    def __init__(self, val, succ=None):
        self.val = val
        self.succ = succ

    def __str__(self):
        return '[{}]->{}'.format(self.val, self.succ)

    def __repr__(self):
        return self.__str__()

    def __len__(self):
        '''if self.succ:
            return 1+self.succ.__len__()
        return 1 '''
        l=self
        c=1
        while l.succ:
            l=l.succ
            c+=1
        return c

    def __add__(self, other):
        reslist=ListaElem(self.val)
        prev=reslist
        l=self.succ
        while l:
            ne=ListaElem(l.val)
            prev.succ=ne
            prev=ne
            l=l.succ
        l=other
        while l:
            ne=ListaElem(l.val)
            prev.succ=ne
            prev=ne
            l=l.succ
        return reslist 

    def get(self, posiz):
        '''if not posiz:
            return self.val
        elif self.succ:
            return self.succ.get(posiz-1)
        else:
            raise IndexError'''
        l=self
        while posiz > 0 and l.succ:
            posiz-=1
            l=l.succ
        if posiz==0:
            return l.val
        raise IndexError
            

        
    def cerca(self, x):
        '''if self.val == x:
            return True
        elif self.succ:
            return self.succ.cerca(x)
        else:
            return False'''
        l=self
        while l:
            if l.val==x:
                return True
            l=l.succ
        return False
   
        
def gen_lista(lista):
    if not lista:
        return None
    return ListaElem(lista[0], gen_lista(lista[1:]))

def gen_lista_iter(lista):
    reslist=ListaElem(lista[0])
    l=reslist
    for i in lista[1:]:
        ne=ListaElem(i)
        l.succ=ne
        l=ne
    return reslist 
    
def gen_lista_iter2(lista):
    l=None
    for i in reversed(lista):
        l=ListaElem(i, l)
    return l
     
l1=ListaElem(2, ListaElem(4, ListaElem(9)))
print(l1)
l=gen_lista([5,7,3,2,8,1,6])
print (l) # stampa [5]->[7]->[3]->[2]->[8]->[1]->[6]->None
l=gen_lista_iter([5,7,3,2,8,1,6])
print (l) # stampa [5]->[7]->[3]->[2]->[8]->[1]->[6]->None
l=gen_lista_iter2([5,7,3,2,8,1,6])
print (l) # stampa [5]->[7]->[3]->[2]->[8]->[1]->[6]->None
print(len(l))