【leetcode 2. Add Two Numbers】(链表，模拟）

题目链接

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.

题意：给定两个数的链表逆序，求相加后的结果

思路：模拟

class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        ListNode *ret = new ListNode(0);
        ListNode *cur = ret;
        int sum = 0;
        while (true) {
            if (l1 != NULL) {
                sum += l1->val;
                l1 = l1->next;
            }
            if (l2 != NULL) {
                sum += l2->val;
                l2 = l2->next;
            }
            cur->val = sum % 10;
            sum /= 10;
            if (l1 != NULL || l2 != NULL || sum)
                cur = (cur->next = new ListNode(0));
            else
                break;
        }
        return ret;
    }
};