You are given two linked lists representing two non-negative numbers. The most significant digit comes first and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.
Follow up:
What if you cannot modify the input lists? In other words, reversing the lists is not allowed.
Example:
Input: (7 -> 2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 8 -> 0 -> 7
# Definition for singly-linked list.
# class ListNode(object):
# def __init__(self, x):
# self.val = x
# self.next = None class Solution(object):
def addTwoNumbers(self, l1, l2):
"""
:type l1: ListNode
:type l2: ListNode
:rtype: ListNode
Input: (7 -> 2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 8 -> 0 -> 7 7->2->4->3
5->6->4
=-------------
7->7->0->7
->1
"""
s1,s2 = [],[]
p1,p2 = l1,l2
while p1:
s1.append(p1.val)
p1 = p1.next
while p2:
s2.append(p2.val)
p2 = p2.next
carry = 0
fake_head = ListNode(None)
while s1 or s2 or carry:
v1 = s1.pop() if s1 else 0
v2 = s2.pop() if s2 else 0
val = v1 + v2 + carry
if val >= 10:
val -= 10
carry = 1
else:
carry = 0
head = ListNode(val)
head.next = fake_head.next
fake_head.next = head
return fake_head.next