LeetCode/2_Add_Two_Numbers.py at main · AnmolPatel20/LeetCode · GitHub

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"""
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.

"""

# 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]:
        result = ListNode(0)
        ptr = result
        carry = 0

        while l1 is not None or l2 is not None:
            total = carry

            if l1 is not None:
                total += l1.val
                l1 = l1.next

            if l2 is not None:
                total += l2.val
                l2 = l2.next

            carry = total // 10
            digit = total % 10
            ptr.next = ListNode(digit)
            ptr = ptr.next

        if carry > 0:
            ptr.next = ListNode(carry)

        return result.next