2. Add Two Numbers

Posted 2020-10-14 Learning is fun.

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 contain a single digit. Add the two numbers and return it as a linked list.

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

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

 

 1 # Definition for singly-linked list.
 2 # class ListNode(object):
 3 #     def __init__(self, x):
 4 #         self.val = x
 5 #         self.next = None
 6 
 7 class Solution(object):
 8     def addTwoNumbers(self, l1, l2):
 9         """
10         :type l1: ListNode
11         :type l2: ListNode
12         :rtype: ListNode
13         """
14         head = ListNode(0)
15         l = head
16         carry = 0
17         while l1 or l2 or carry:
18             s = carry; carry = 0
19             if l1:
20                 s += l1.val
21                 l1 = l1.next
22             if l2:
23                 s += l2.val
24                 l2 = l2.next
25             if s > 9:
26                 s -= 10
27                 carry += 1
28             l.next = ListNode(s)
29             l = l.next
30         return head.next