2. Add Two Numbers 【M】【72】【leetcode】

sscssz

于 2016-03-31 17:48:41 发布

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分类专栏： Python leetcode 算法数据结构链表文章标签： leetcode题解 python 链表

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本文介绍了一种算法，该算法接收两个表示非负整数的链表，并将它们相加，结果同样以链表形式返回。重点讲解了如何处理进位、不同长度的链表输入等问题。

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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

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三个地方需要注意，一个是有进位，一个是两个数位数不一定等长，一个是，最后可能还会有个1 的进位

class Solution(object):
    def addTwoNumbers(self, l1, l2):

        carry = 0
        res = ListNode(0)
        head = res

        while l1 and l2:
            #print l1.val,l2.val
            temp = (l1.val + l2.val + carry)
            if temp > 9:
                temp = temp % 10
                carry = 1
            else:
                carry = 0
            l1 = l1.next
            l2 = l2.next
            res.next = ListNode(temp)
            res = res.next

        while l1:
            temp = l1.val + carry
            if temp > 9:
                temp = temp % 10
                carry = 1
            else:
                carry = 0
            l1 = l1.next
            res.next = ListNode(temp)
            res = res.next

        while l2:
            temp = l2.val + carry
            if temp > 9:
                temp = temp % 10
                carry = 1
            else:
                carry = 0
            l2 = l2.next
            res.next = ListNode(temp)
            res = res.next
        if carry == 1:
            res.next = ListNode(1)

        return head.next