linkedList.py

import os,msvcrt
class node_ll:
    def __init__(self, data = None):
        self.val = data
        self.pointer = None
    
    def __repr__(self):
        return str(self.val)


class LinkedList :
    # node = 7

    def __init__(self):
        self.headNode = node_ll()

    def __len__(self):
        _,total_nodes = self.nodes()
        return total_nodes

    def show(self):
        print("VLAUES IN LINKED LIST : -")
        n = self.headNode
        while n.pointer != None :
            print(n.val , end = " -> ")
            n = n.pointer
        print(n.val)
    
    def add_node(self,value = None):
        n = self.headNode
        if n.val == None: self.headNode.val = value
        else:
            while n.pointer != None:
                n = n.pointer
            n.pointer = node_ll(value)
            # self.nodes +=1

    def pop(self):
        n = self.headNode
        temp = self.headNode
        while True:
            if n.pointer == None:
                temp.pointer = None
                break
            n = n.pointer
            temp = n
        # self.nodes -= 1
        
    def remove_duplicates(self):
        values = set()
        n = self.headNode
        while True:
            if n.val not in values: 
                values.add(n.val)
                n = n.pointer
            else:
                # print(f'this node = {n.val}, next = {n.pointer.val}')
                n.val = n.pointer.val
                n.pointer = n.pointer.pointer
                # if n.val not in values: values.add(n.val)
            if n.pointer == None: break 
            # print(n.val)
            # n = n.pointer
            

    def kthNode(self, k = 0):
        if k < 0:
            n = self.headNode
            nodes = 0
            while True:
                nodes += 1
                if n.pointer == None: break
                n = n.pointer
                
            n = self.headNode
            i = 0
            
            while i < nodes + k+1:
                if i == nodes+k: return(n.val)
                n = n.pointer
                i += 1
        else:
            n = self.headNode
            while k != 0:
                k -= 1
                if k == 0: return(n.val)
                n = n.pointer
            return n.val
                                
    def nodes(self):
        values = []
        n = self.headNode
        total_nodes = 0
        while True:
            values.append(n.val)
            if n.pointer == None: break
            n = n.pointer
            total_nodes += 1
        return values , total_nodes

    def __getitem__(self, kth):
        return self.kthNode(kth)

    def __bool__(self):
        return self.headNode.val != None

    def __str__(self):
        values , _ = self.nodes()
        values = list(map(str,values))
        return ' -> '.join(values)

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

    def __add__(self, other):
        assert(isinstance(other, LinkedList))
        n1 = self.headNode
        n2 = other.headNode
        new_list = self.__class__()
        quo = 0
        while True:
            try: 
                v1 = n1.val
                n1 = n1.pointer
            except: v1 = 0

            try: 
                v2 = n2.val
                n2 = n2.pointer
            except: v2 = 0

            s = v1+v2  
            if quo: s+=1
            rem = s%10
            quo = s//10
            # print(rem)
            new_list.add_node(rem)
            if n1 == None and n2 == None: break
        return new_list
        # else: raise Exception

    def isPalindrome(self):
        stack = []
        slow = self.headNode
        fast = self.headNode
        odd_flag = True

        while True:
            stack.append(slow.val)
            if fast.pointer.pointer: fast = fast.pointer.pointer
            else:
                fast = fast.pointer
                odd_flag = False
            # print(fast)
            if fast.pointer == None: break
            slow = slow.pointer
            
        if odd_flag : slow = slow.pointer

        while True:
            if slow.pointer : slow = slow.pointer
            else : break 
            if stack.pop() != slow.val: return False

        return True

            
list1 = LinkedList()
list1.add_node(1)
list1.add_node(2)
list1.add_node(3)
list1.add_node(4)
list1.add_node(3)
list1.add_node(2)
list1.add_node(1)

print(list1.isPalindrome())
# print(list1)

# list2 = LinkedList() 
# list2.add_node(5)
# list2.add_node(9)
# list2.add_node(2)
# print(list2)

# n = list1 + list2
# print(n)


# n.show()

# n1 ,n2 = list1.headNode, list2.headNode

# while True:
#     try: 
#         v1 = n1.val
#         n1 = n1.pointer
#     except: v1 = 0

#     try: 
#         v2 = n2.val
#         n2 = n2.pointer
#     except: v2 = 0



# v = 0

# while v != 5:
#     os.system('cls')
#     print('1. Add value to LL \n2. See values \n3. Remove Duplicates \n5. Exit')
#     v = int(input('Enter choice :-'))
#     if v==1:
#         os.system('cls')
#         value = 0
#         while value != 'q' and value != 'Q':
#             value = input('Enter Values to add (at the end) in Linked List :-> ')
#             if value != 'q' and value != 'Q':
#                 list1.add_node(value)
#     if v==2:
#         list1.show()
#         msvcrt.getch()
#     if v==3:
#         list1.remove_duplicates()