CH5ex3.py

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


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

    def __str__(self):
        if self.isEmpty():
            return "Empty"
        cur, s = self.head, str(self.head.value)
        if cur.next != None:
            s += ' '
        while cur.next != None:
            s += str(cur.next.value)
            if cur.next.next != None:
                s += ' '
            cur = cur.next
        return s

    def reverse(self):
        if self.isEmpty():
            return "Empty"
        prev = None
        current = self.head
        while (current is not None):
            next = current.next
            current.next = prev
            prev = current
            current = next
        self.head = prev
        return self.__str__()

    def isEmpty(self):
        return self.head == None

    def append(self, item):
        new_node = Node(item)
        if self.head is None:  # if linked list is empty, then the new_node is head
            self.head = new_node
        else:
            cur = self.head  # define
            while cur.next != None:
                cur = cur.next
            cur.next = new_node
            new_node.previous = cur
            return

    def addHead(self, item):
        new_node = Node(item)
        new_node.next = self.head
        new_node.previous = None
        if self.isEmpty() != True:
            self.head.previous = new_node
        self.head = new_node

    def insert(self, pos, item):
        if self.size() == 0:
            self.append(item)
        else:
            new_node = Node(item)
            if pos >= self.size():
                self.append(item)
            elif pos < (self.size()*-1):
                self.addHead(item)
            elif pos == 0:
                cur = self.head
                new_node.next = cur
                new_node.previous = None
                self.head = new_node
            elif pos == -1:
                cur = self.head
                while cur.next.next != None:
                    cur = cur.next
                new_node.next = cur.next
                new_node.previous = cur
                cur.next = new_node
            elif pos <= 0:
                cur = self.head
                index = self.size()*(-1)
                while cur.next != None and index != pos-1:
                    cur = cur.next
                    index += 1
                new_node.next = cur.next
                new_node.previous = cur
                cur.next = new_node

            else:
                # traverse to target position
                cur = self.head
                count = 0
                while count != pos:
                    cur = cur.next
                    count += 1
                    if count == pos - 1:
                        new_node.next = cur.next
                        cur.next = new_node
                new_node.previous = cur.previous

    def search(self, item):
        found = 0
        count = 0
        cur = self.head
        while count <= self.size()-1:
            count += 1
            if cur.value == item:
                found = 1
            cur = cur.next
        if found == 0:
            return 'Not Found'
        else:
            return 'Found'

    def index(self, item):
        idx = 0
        found = -1
        cur = self.head
        while idx <= self.size()-1:
            idx += 1
            if cur.value == item:
                idx -= 1
                found = 0
                return idx
            cur = cur.next

        return found# if not match any elem

    def size(self):
        if self.head != None:
            count = 1
            cur = self.head
            while cur.next != None:
                cur = cur.next
                count += 1
            return count
        else:
            return 0

    def pop(self, pos):
        if pos < 0 or pos >= self.size():
            return "Out of Range"
        if pos == 0 and self.size() > 0:
            self.head = self.head.next
            return "Success"
        else:
            cur = self.head
            for i in range(0, pos):
                cur = cur.next
            cur.next = cur.next.next
            if i+1 == pos:
                return "Success"
inp = input('Enter Input (L1,L2) : ').split(' ')
ll1 = LinkedList()
ll2 = LinkedList()
#don't forget change input(str) to int
if len(inp[0]) > 1:
    L1 = inp[0].split('->')
else:
    L1 = inp[0]
if len(inp[1]) > 1:
    L2 = inp[1].split('->')
else:
    L2 = inp[1]
print('L1    : ',end='')
for i in L1:
    print(i,end=' ')
    ll1.append(i)

print('\nL2    : ',end='')
for j in L2:
    print(j,end=' ')
    ll2.append(j)
ll2.reverse()
print(f'\nMerge : {ll1} {ll2}')