leetcode2. Add Two Numbers

Posted 2021-01-07 yuchi328

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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.

链表添加节点new的操作，注意最后的进位处理。

 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  */
 9 class Solution {
10 public:
11     ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
12         ListNode res(0);
13         ListNode * nTmp = &res;
14         int carry = 0;
15         while (l1||l2) {
16             int v1,v2;
17             if(l1 == nullptr) v1 = 0;
18             else{
19                 v1 = l1->val;
20                 l1 = l1->next;
21             }
22             if(l2 == nullptr) v2 = 0;
23             else{
24                 v2 = l2->val;
25                 l2 = l2->next;
26             }
27             int cur = (v1 + v2 + carry) % 10;
28             carry = (v1 + v2 + carry) / 10;
29             ListNode * tmp = new ListNode(cur);
30             nTmp->next = tmp;
31             nTmp = nTmp->next;
32         }
33         if(carry){
34             ListNode * tmp = new ListNode(carry);
35             nTmp->next = tmp;
36             nTmp = nTmp->next;
37         }
38         return res.next;
39     }
40 };