title: LeetCode 2. Add Two Numbers
level: Medium

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

warning >>> status: Runtime Error

# 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: ListNode, l2: ListNode) -> ListNode:
        firstNumber = []
        secondNumber = []
        
        while l1 is not None:
            firstNumber.append(l1.val)
            secondNumber.append(l2.val)
            #print(l1.val)
            #print(l2.val)
            l1 = l1.next
            l2 = l2.next 
        #print(firstNumber)
        #print(secondNumber)
        firstNumber.reverse()
        secondNumber.reverse()
        print(firstNumber)
        print(secondNumber)
        ans = []
        inin = 0
        for i in range(len(firstNumber)):
            tmp = firstNumber[i]+secondNumber[i]
            
            if inin == 1:
                tmp = tmp + 1
                if tmp < 10:
                    inin = 0
            
                
            if tmp >= 10:
                inin = 1
                tmp = tmp-10
                
            ans.append(tmp)
        if inin==1:
            ans.append(inin)
        print(ans)
        #ListNode out
        #out = ListNode()
        
        result = ListNode(0)
        node = result
        
        for i in range(len(ans)):
            node.next = ListNode(ans[i])
            node = node.next

                
        return result.next

TODO : Fix it & share how
補(20'09'19): 直接以 link list 理解

# 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: ListNode, l2: ListNode) -> ListNode:
        result = ListNode(0)
        node = result
        temp = 0
        while l1 is not None or l2 is not None or temp>0:
            if l1 is not None:
                temp += l1.val
                l1 = l1.next
            if l2 is not None:
                temp += l2.val
                l2 = l2.next
            node.next = ListNode(temp%10)   # 取個位數
            node = node.next
            temp = temp // 10    # 檢查是否要進位
        return result.next

ref : 網路