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9.py
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9.py
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# Add two numbers represented by linked lists
# Given two numbers represented by two linked lists of size N and M. The task is to return a sum list.
# The sum list is a linked list representation of the addition of two input numbers from the last.
class Node:
def __init__(self, data):
self.data = data
self.next = None
class Solution:
# reversing a given linked list
def reverse(self, head):
curr = head
prev = None
next = None
while curr != None:
next = curr.next
curr.next = prev
prev = curr
curr = next
return prev
def add_two_ll(self, first, second):
first = self.reverse(first)
second = self.reverse(second)
c = 0 # carry
s = 0 # sum
res = None
curr = None
while first != None or second != None:
s = c + ( first.data if first else 0 ) + (second.data if second else 0) # checking if the node exist, if it does not then we take 0 as its value
c = ( 1 if s >= 10 else 0 ) # if sum is greater than 10 then carry is 1 else it is zero
s = s % 10
# creating the new linked list
temp = Node(s)
# declaring the head of the new linked list
if res == None:
res = temp
else:
curr.next = temp # adding the new node, temp.
curr = temp
# moving the nodes
if first: first = first.next
if second: second = second.next
# if carry is left
if c > 0:
temp = Node(c)
curr.next = temp
curr = temp
# reversing the list to get the correct order
res = self.reverse(res)
return res