Leetcode linked list algorithm

Add two numbers

Difficulty: medium Type: linked list

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Two non-empty linked lists are given to represent two non-negative integers. Among them, their respective digits are stored in reverse order, and each of their nodes can only store one digit.

If we add these two numbers together, a new linked list will be returned to represent their sum.

You can assume that except for the number 0, neither of these numbers will start with 0.

Examples

Input: (2-> 4-> 3) + (5-> 6-> 4)
Output: 7-> 0-> 8
Reason: 342 + 465 = 807

Problem-solving ideas

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The two lists are traversed at the same time, added bit by bit, and the carry is retained

Code

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
# self.next = None class Solution: def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode: dummy = ListNode(0) cur = dummy carry = 0 while l1 or l2: num1 = l1.val if l1 else 0 num2 = l2.val if l2 else 0 sum = num1 + num2 + carry carry = sum // 10 cur.next = ListNode(sum%10) cur = cur.next l1 = l1.next if l1 else None l2 = l2.next if l2 else None if carry: cur.next = ListNode(carry) return dummy.next

Author: wzNote
link: https: //www.jianshu.com/p/8ea60c68cde7
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