add_two_numbers_ii.py

'''
You are given two non-empty linked lists representing two non-negative integers. The most significant digit comes first and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.
'''


class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
        
        
        s1,s2=0,0
        
        while l1!=None:
            s1=s1*10+l1.val
            l1=l1.next
        
        while l2!=None:
            s2=s2*10+l2.val
            l2=l2.next
        
        
        dummylist=dummy=ListNode(0)
        
        for i in str(s1+s2):
            dummy.next=ListNode(i)
            dummy=dummy.next
        
        return dummylist.next