Add Two Numbers

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

題意：輸入兩個連結串列，對應位相加，並且進位到下一位。

/**
 * 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 *ans = new ListNode(0
 
), *p = ans;
        int cur = 0;
        while(l1 != NULL || l2 != NULL || cur)
        {
            p->val = (l1 ? l1->val : 0) + (l2 ? l2->val : 0) + cur;
            cur = p->val / 10;
            p->val %= 10;
            if(l1) l1 = l1->next;
            if(l2) l2 = l2->next;
            if
 
(l1 || l2 || cur)
                p->next = new ListNode(0);
            p = p->next;
        }
        return ans;
    }
};