445. Add Two Numbers II
Đề Bài
You are given two non-empty linked lists representing two non-negative integers. The most significant digit comes first 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 = [7,2,4,3], l2 = [5,6,4] Output: [7,8,0,7]
Example 2:
Input: l1 = [2,4,3], l2 = [5,6,4] Output: [8,0,7]
Example 3:
Input: l1 = [0], l2 = [0] Output: [0]
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.
Follow up: Could you solve it without reversing the input lists?
Thuật Toán & Kỹ Thuật
⏱️ Thời gian
O(n)
💾 Không gian
O(n)
Lời Giải
Python
0445-add-two-numbers-ii.py
# Definition for singly-linked list.
# class ListNode:
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next
class Solution:
def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
if not head:
return None
currNode = head
nextNode = head.next
prevNode = None
while currNode and nextNode:
currNode.next = prevNode
prevNode = currNode
currNode = nextNode
nextNode = nextNode.next
currNode.next = prevNode
prevNode = currNode
return prevNode
def addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:
l1 = self.reverseList(l1)
l2 = self.reverseList(l2)
l3 = ListNode(0)
cr = l3
carry = 0
while l1 or l2 or carry:
total = carry
if l1:
total += l1.val
l1 = l1.next
if l2:
total += l2.val
l2 = l2.next
cr.next = ListNode(total % 10)
cr = cr.next
carry = total // 10
return self.reverseList(l3.next)