[Python-Leetcode] 2. Add Two Numbers (difficulty : Medium - ☆☆)

문제 설명 2. Add Two Numbers

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.

 

문제 풀이

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

class Solution:
    def addTwoNumbers(self, l1:ListNode, l2:ListNode)->ListNode:
        
        root = current = ListNode()
        carry = 0 
        val = 0
        while l1 or l2 or carry:
            if not l1:
                l1 = ListNode()
            if not l2:
                l2 = ListNode()

            carry, val = divmod(l1.val + l2.val + carry, 10)
            l1 = l1.next
            l2 = l2.next
            current.next = ListNode(val)
            current = current.next
        
        return root.next