[Leetcode]2. Add Two Numbers

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.

C++代码

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        ListNode* res;
        res = new ListNode(-1);
        int temp=0;
        ListNode* tmp = res;
        ListNode* p1 = l1;
        ListNode* p2 = l2;
        while(p1 != NULL || p2 != NULL){
            int sum = temp;
            if(p1 != NULL){
                sum += p1->val;
                p1 = p1->next;
            }
            if(p2 != NULL){
                sum += p2->val;
                p2 = p2->next;
            }
            tmp->next = new ListNode(sum%10);
            temp = sum/10;
            tmp = tmp->next;
        }
        if(temp) tmp->next = new ListNode(1);

        return res->next;
    }
};