Silly Solution:
python
# Definition for singly-linked list.
# class ListNode:
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next
class Solution:
def addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:
pre1, cur1 = None, l1
pre2, cur2 = None, l2
while cur1:
tmp = cur1.next
cur1.next = pre1
pre1 = cur1
cur1 = tmp
head1 = pre1
while cur2:
tmp = cur2.next
cur2.next = pre2
pre2 = cur2
cur2 = tmp
head2 = pre2
n1 = ''
n2 = ''
while head1:
n1 += str(head1.val)
head1 = head1.next
while head2:
n2 += str(head2.val)
head2 = head2.next
r = reversed(str(int(n1) + int(n2)))
# head insertion
dummy = ListNode()
cur = dummy
for i in r:
node = ListNode(int(i))
cur.next = node
cur = node
return dummy.nextThere is one thing need to be noticed:
Head insertion:
python
# 初始化头节点
head = ListNode(arr[0])
current = head
# 逐个创建后续节点
for value in arr[1:]:
node = ListNode(value)
current.next = node
current = node
return head