Medium
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?
# 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]:
num1 = self.nodeToNumber(l1)
num2 = self.nodeToNumber(l2)
answer = num1+num2
return self.reverseLL(self.numberToNode(num1 + num2))
def reverseLL(self, head):
prev = None
node = head
while node:
temp = node.next
node.next = prev
prev = node
node = temp
return prev
def nodeToNumber(self, head):
number = 0
node = head
while node:
number = number*10 + node.val
node = node.next
return number
def numberToNode(self, number):
head = ListNode(0)
node = head
if number == 0:
return head
while number!=0:
digit = number%10
new_node = ListNode(digit)
node.next = new_node
node = new_node
number = number// 10
return head.next