PalindromeLinkedList.py

# Given a string and using linked lists
# determine whether the string is a palindrome
import unittest

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


class LinkedList:
    def __init__(self):
        self.head = None
        self.length = 0

    def append(self, data):
        new_node = Node(data)
        if self.head is None:
            self.head = new_node
        else:
            current = self.head
            while current.next is not None:
                current = current.next
            current.next = new_node

        self.length += 1

    def append_node(self, new_node):
        if self.head is None:
            self.head = new_node
        else:
            current = self.head
            while current.next is not None:
                current = current.next
            current.next = new_node

        self.length += 1

    def prepend(self, data):
        self.head = Node(data, self.head)
        self.length += 1

    def prepend_node(self, noded):
        noded.next = self.head
        self.head = noded

    def __str__(self):
        string = "["
        current = self.head
        while current is not None:
            string += str(current.data)
            current = current.next
            if current is not None:
                string += ","

        return string + "]"



def Palindrome_check(list1):
    list2 = LinkedList()
    current = list1.head
    while current is not None:
        list2.prepend(current.data)
        current = current.next
    current1 = list1.head
    current2 = list2.head
    while current1 is not None:
        if current1.data is not current2.data:
            return False
            break
        current1 = current1.next
        current2 = current2.next
    return True



# setup for tests 
list1 = LinkedList()
list2 = LinkedList()
list3 = LinkedList()
list4 = LinkedList()
list1.append("a")
list1.append("b")
list1.append("a")
list2.append("x")
list2.append("x")
list2.append("t")
list2.append("z")
list2.append("z")
list3.append("")
list4.append("r")
list4.append("y")
list4.append("i")
list4.append("t")
list4.append("t")
list4.append("i")
list4.append("y")
list4.append("r")
class Test(unittest.TestCase):
    
    def test_Palindrome_check(self):
        self.assertEqual(Palindrome_check(list1), True)
        self.assertEqual(Palindrome_check(list2), False)
        self.assertEqual(Palindrome_check(list3), True)
        self.assertEqual(Palindrome_check(list4), True)
        
unittest.main()