Question

I’m attempting to create a linked list of length n using Python. I have the simple list implemented, a working concatenation function, and a working create_list function; however, I just want to know if there is a more efficient method at making the linked list than using my concatenate function (made for testing).

Simple List Class:

class Cell:

    def __init__( self, data, next = None ):
        self.data = data
        self.next = next

Concatenate Function:

def list_concat(A, B):
    current = A
    while current.next != None:
        current = current.next
    current.next = B
    return A

List create (that takes forever!):

def create_list(n):
    a = cell.Cell(0)
    for i in (range(1,n)):
        b = cell.Cell(i)
        new_list = cell.list_concat(a, b)   
    return new_list

Answer 1

The simplest way to improve your code is this:

def create_list(n):
    new_list = cell.Cell(0)
    last_a = new_list
    for i in (range(1,n)):
        a = cell.Cell(i)
        cell.list_concat(last_a, a)
        last_a = a
    return new_list

This will bring the complexity of the approach down to O(n) from O(n**2).