[FIXED] Finding the length of a linked list in python

Issue

def len_link(lst):

"""Returns the length of the link.

    >>> lst = link(1, link(2, link(3, link(4))))
    >>> len_link(lst)
    4
    >>> len_link(empty)
    0
    """

Hi I'm having a hard time understanding how to find the length of a linked list if someone could help I would really appreciate it.

Solution

As stated in "Functional linked lists in Python":

The length operation returns the number of elements in a given list. To find the length of a list we need to scan all of its n elements. Therefore this operation has a time complexity of O(n).

def length(xs):
    if is_empty(xs):
        return 0
    else:
        return 1 + length(tail(xs))

assert length(lst(1, 2, 3, 4)) == 4
assert length(Nil) == 0

head and tail are respectively:

def head(xs):
    return xs[0]

assert head(lst(1, 2, 3)) == 1
def tail(xs):
    return xs[1]

assert tail(lst(1, 2, 3, 4)) == lst(2, 3, 4)

Answered By - Abhishek Dey