leetcode 2. Add Two Numbers

2. Add Two Numbers

Total Accepted: 123735 Total Submissions: 554195 Difficulty: Medium

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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Linked List Math

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new 新的节点参考了：

http://blog.csdn.net/feliciafay/article/details/16978487

核心代码：

1 ListNode *p = new ListNode(sum % 10);
2

比较好的思路：

直接用了取余和 /10 操作，少一步判断是否要进位。

 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* tail = NULL;
13         ListNode* head = NULL;
14         int sum = 0;
15         while(l1 != NULL || l2 != NULL){
16             if(l1 != NULL){
17                 sum += l1->val;
18                 l1 = l1->next;
19             }
20             if(l2 != NULL){
21                 sum += l2->val;
22                 l2 = l2->next;
23             }
24             ListNode *p = new ListNode(sum % 10);
25             if (head == NULL) {  
26                 head = p;  
27                 tail = p;  
28             } else {  
29                 tail->next = p;  
30                 tail = p;  
31             }  
32             sum /= 10;
33         }
34         if(sum != 0){
35             ListNode *p = new ListNode(sum % 10);
36             tail->next = p;  
37             tail = p;  
38         }
39         tail->next = NULL;
40         return head;
41     }
42 };