mirror of
https://github.com/prdlk/leetcode.git
synced 2026-11-02 13:12:44 +00:00
88 lines
2.8 KiB
Plaintext
88 lines
2.8 KiB
Plaintext
---
|
|
title: '2. Add Two Numbers'
|
|
description: 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
|
|
icon: dot
|
|
topics:
|
|
- { name: "Linked List", slug: "linked-list" }
|
|
- { name: "Math", slug: "math" }
|
|
- { name: "Recursion", slug: "recursion" }
|
|
video: "wgFPrzTjm7s"
|
|
issue: "https://github.com/prdlk/leetcode/issues/88"
|
|
companies:
|
|
- { name: "Ola Cabs", period: "Thirty Days", frequency: 95.8 }
|
|
- { name: "Bloomberg", period: "Thirty Days", frequency: 83.1 }
|
|
- { name: "Google", period: "Thirty Days", frequency: 72.8 }
|
|
- { name: "Microsoft", period: "Thirty Days", frequency: 67.9 }
|
|
- { name: "Meta", period: "Thirty Days", frequency: 63.8 }
|
|
- { name: "Amazon", period: "Thirty Days", frequency: 61.3 }
|
|
- { name: "EarnIn", period: "Six Months", frequency: 100 }
|
|
- { name: "Jane Street", period: "Six Months", frequency: 100 }
|
|
- { name: "Palo Alto Networks", period: "Six Months", frequency: 75.9 }
|
|
- { name: "tcs", period: "Six Months", frequency: 43.5 }
|
|
sidebar:
|
|
label: 'Add Two Numbers'
|
|
badge: 'Medium'
|
|
---
|
|
|
|
### 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.
|
|
|
|
## Approach
|
|
|
|
```mermaid
|
|
flowchart TD
|
|
S(["addTwoNumbers(l1, l2)"]) --> I["dummy = ListNode(), carry = 0, curr = dummy — dummy.next will be the head"]
|
|
I --> W{"l1 or l2 or carry?"}
|
|
W -- no --> E(["return dummy.next"])
|
|
W -- yes --> A["s = (l1.val if l1 else 0) + (l2.val if l2 else 0) + carry — a missing digit counts as 0"]
|
|
A --> D["carry, val = divmod(s, 10)"]
|
|
D --> N["curr.next = ListNode(val), curr = curr.next"]
|
|
N --> V["l1 = l1.next if l1 else None, l2 = l2.next if l2 else None"]
|
|
V --> W
|
|
```
|
|
|
|
## Solution
|
|
|
|
```py
|
|
# 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]:
|
|
|
|
dummy = ListNode()
|
|
carry = 0
|
|
curr = dummy
|
|
while l1 or l2 or carry:
|
|
s = (l1.val if l1 else 0) + (l2.val if l2 else 0) + carry
|
|
carry, val = divmod(s, 10)
|
|
|
|
curr.next = ListNode(val)
|
|
curr = curr.next
|
|
|
|
l1 = l1.next if l1 else None
|
|
l2 = l2.next if l2 else None
|
|
|
|
return dummy.next
|
|
```
|