Leetcode 算法 - 2. Add Two Numbers
Posted August 16, 2016
问题链接: 2. Add Two Numbers
问题描述: You are given two linked lists representing two non-negative numbers. 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.
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
使用语言: Python
需要注意的是: 这里使用的ListNode不是Python内置的list对象, 而是传统(计算机科学)意义上的列表, 通常叫做Linked list(链表), 通常由一系列节点实现, 其每个节点中都持有一个指向下一个节点的引用. 这里就是next属性. 链表分为单向链表和双向链表. 双向链表持有一个指向前一节点的引用.
# 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
"""
x1, x2 = l1, l2
results = ListNode(0)
p = results
while True:
if not x1 and not x2 and not p.next:
break
if p.next:
c = getattr(x1, 'val', 0) + getattr(x2, 'val', 0) + flag.next.val
else:
c = getattr(x1, 'val', 0) + getattr(x2, 'val', 0)
flag = ListNode(c % 10)
if c >= 10:
flag.next = ListNode(c / 10)
p.next = flag
p = flag
x1 = x1.next if isinstance(x1, ListNode) else None
x2 = x2.next if isinstance(x2, ListNode) else None
return results.next