[LeetCode] 2. Add Two Numbers 两个数字相加

落日映苍穹つ 2022-10-02 10:57 161阅读 0赞

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.

给定两个链表分别代表两个非负整数。数位以倒序存储，并且每一个节点包含一位数字。将两个数字相加并以链表形式返回。题目不难，主要考察链表操作和加法进位。

进位 = sum / 10，当前位值 = sum % 10

python代码：

class ListNode(object):
        def __init__(self, x):
            self.val = x
            self.next = None
    
    class Solution:
        # @return a ListNode
        def addTwoNumbers(self, l1, l2):
            head = ListNode(0)
            l = head
            carry = 0
            while l1 or l2 or carry:
                sum, carry = carry, 0
                if l1:
                    sum += l1.val
                    l1 = l1.next
                if l2:
                    sum += l2.val
                    l2 = l2.next
                if sum > 9:
                    carry = 1
                    sum -= 10
                l.next = ListNode(sum)
                l = l.next
            return head.next
    
    if __name__=='__main__':
        a, a.next, a.next.next = ListNode(2), ListNode(4), ListNode(3)
        b, b.next, b.next.next = ListNode(5), ListNode(6), ListNode(4)
        result = Solution().addTwoNumbers(a, b)
        print("{0} -> {1} -> {2}".format(result.val, result.next.val, result.next.next.val))