[Problem]
You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, 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.
Example 1:
Input: l1 = [2,4,3], l2 = [5,6,4]
Output: [7,0,8]
Explanation: 342 + 465 = 807.
Example 2:
Input: l1 = [0], l2 = [0]
Output: [0]
Example 3:
Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
Output: [8,9,9,9,0,0,0,1]
Constraints:
- The number of nodes in each linked list is in the range [1, 100].
- 0 <= Node.val <= 9
- It is guaranteed that the list represents a number that does not have leading zeros.
[Solution]
class Solution:
def addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:
result = ListNode()
cursor = result
while l1 or l2:
l1 = l1 or ListNode()
l2 = l2 or ListNode()
sum = cursor.val + l1.val + l2.val
if sum >= 10:
cursor.next = ListNode(val = 1)
elif l1.next or l2.next:
cursor.next = ListNode(val = 0)
cursor.val = sum % 10
l1 = l1.next
l2 = l2.next
cursor = cursor.next
return result
If l1 length is different from l2 length, I append zero into shorter list to equalize each other's length.
l1 | 5 | 7 | 1 | 2 | 6 | 9 |
l2 | 8 | 2 | 0 | 0 | 0 | 0 |
After making each other's lengths equal, this problem can be solved as other plus operation problems.
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