LeetCode [Day 4] Add Two Numbers 题解

Add Two Numbers

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

思路

类似于高精度加法，只不过是用链表实现。我比较懒，只想写这么多。

代码

1/**
2 * Definition for singly-linked list.
3 * struct ListNode {
4 *     int val;
5 *     ListNode *next;
6 *     ListNode(int x) : val(x), next(NULL) {}
7 * };
8 */
9class Solution {
10public:
11    ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
12        ListNode *ret = new ListNode(0);
13        ListNode *head = ret;
14        int extra = 0;
15        int ans = 0;
16        while (l1 != NULL || l2 != NULL) {
17            if (l1 != NULL) {
18                ans += l1->val;
19                l1 = l1->next;
20            }
21            if (l2 != NULL) {
22                ans += l2->val;
23                l2 = l2->next;
24            }
25            ans += extra;
26            extra = ans/10;
27            ans %= 10;
28            ListNode *node = new ListNode(ans);
29            head->next = node;
30            head = node;
31            ans = 0;
32        }
33        if (extra != 0) {
34            ListNode *node = new ListNode(extra);
35            head->next = node;
36            head = node;
37        }
38        return ret->next;
39    }
40};