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题目：
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：
题目比较简单，关键在于用一个变量记录是否有进位即可，同时遍历两个链表，每次将 val 和进位相加，将和的个位存到新的链表，和的十位记录到进位中，直到链表遍历完成。
代码：
1 /** 2 * Definition for singly-linked list. 3 * struct ListNode { 4 * int val; 5 * struct ListNode *next; 6 * }; 7 */ 8 struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) { 9 struct ListNode * result = NULL, * last = NULL, *last1 = l1, *last2 = l2; 10 int decade = 0, sum = 0; 11 12 result = malloc(sizeof(struct ListNode)); 13 sum = last1->val + last2->val; 14 result->val = sum % 10; 15 last = result; 16 last1 = last1->next; 17 last2 = last2->next; 18 decade = sum / 10; 19 while (last1 && last2){ 20 sum = last1->val + last2->val + decade; 21 last->next = malloc(sizeof(struct ListNode)); 22 last = last->next; 23 last->val = sum % 10; 24 decade = sum / 10; 25 last1 = last1->next; 26 last2 = last2->next; 27 } 28 while (last1){ 29 last->next = malloc(sizeof(struct ListNode)); 30 last = last->next; 31 sum = last1->val + decade; 32 last->val = sum % 10; 33 last1 = last1->next; 34 decade = sum / 10; 35 } 36 while (last2){ 37 last->next = malloc(sizeof(struct ListNode)); 38 last = last->next; 39 sum = last2->val + decade; 40 last->val = sum % 10; 41 last2 = last2->next; 42 decade = sum / 10; 43 } 44 if (decade == 1){ 45 last->next = malloc(sizeof(struct ListNode)); 46 last = last->next; 47 last->val = 1; 48 } 49 last->next = NULL; 50 return result; 51 }
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原文地址：http://www.cnblogs.com/YaolongLin/p/4850947.html
