Description: You are given two non-empty linked lists representing two non-negative integers. 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.

Link: https://leetcode.com/problems/add-two-numbers-ii/

Examples:

Input: (7 -> 2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 8 -> 0 -> 7

思路: 將兩個連結串列表示的非負值相加，結果以連結串列的形式返回。下面的方法時間和空間複雜度都不是很好。

class Solution(object):
    def addTwoNumbers(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        
 
"""
        def get_numbers(l):
            p = l
            numbers = []
            while p:
                numbers.append(p.val)
                p = p.next
            value = 0
            for i, v in enumerate(numbers):
                value += v*pow(10, len(numbers)-1-i)
            return value
        
        n1 
 
= get_numbers(l1)
        n2 = get_numbers(l2)
        n = n1+n2
        r = ListNode(0)
        rhead = r
        for c in str(n):
            node = ListNode(int(c), None)
            r.next = node
            r = r.next
        return rhead.next

日期: 2020-12-03 畫了兩天的圖，我也是夠了。