55_Add_Two_Numbers_II

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
def reverse(head):
    curr=head
    prev=None
    nex=None
    while curr!=None:
        nex=curr.next
        curr.next=prev
        prev=curr
        curr=nex
    return prev
class Solution:
    def addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:
        l1=reverse(l1)
        l2=reverse(l2)
        carry=0
        ans=ListNode()
        ptr3=ans
        ptr1=l1
        ptr2=l2
        while ptr1 or ptr2:
            if ptr1 and ptr2:
                s=ptr1.val+ptr2.val+carry
                carry=s//10
                s=s%10
                temp=ListNode(s)
                ptr3.next=temp
                ptr3=ptr3.next
                ptr1=ptr1.next
                ptr2=ptr2.next
            elif ptr1:
                s=ptr1.val+carry
                carry=s//10
                s=s%10
                temp=ListNode(s)
                ptr3.next=temp
                ptr3=ptr3.next
                ptr1=ptr1.next
            elif ptr2:
                s=ptr2.val+carry
                carry=s//10
                s=s%10
                temp=ListNode(s)
                ptr3.next=temp
                ptr3=ptr3.next
                ptr2=ptr2.next
        if carry:
            temp=ListNode(carry)
            ptr3.next=temp
        return reverse(ans.next)