Add Two Numbers

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
        s1=''
        while(l1 is not None):
            s1+=str(l1.val)
            l1=l1.next
        s2=''
        while(l2 is not None):
            s2+=str(l2.val)
            l2=l2.next
        ans=int(s1[::-1])+int(s2[::-1])
        ans=str(ans)
        # createlist(ans)
        head=None
        sec=None
        for x in ans:
            if(head==None):
                head=ListNode(int(x))
                # head.next=None
            else:
                sec=ListNode(int(x))
                sec.next=head
                head=sec
                sec=None
        return head