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.
这个题目就是求和，但是要考虑进位问题。
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 head(0); 13 ListNode* pre = &head; 14 if(!l1)return l2; 15 if(!l2)return l1; 16 int extra = 0; 17 while(l1||l2||extra){ 18 if(l1){ 19 extra += l1->val; 20 l1 = l1->next; 21 } 22 if(l2){ 23 extra += l2->val; 24 l2 = l2->next; 25 } 26 pre->next = new ListNode(extra%10); 27 extra = extra/10; 28 pre = pre->next; 29 } 30 return head.next; 31 } 32 };
