leetcode 刷题题解（c++） 2.Add Two Numbers （链表）

题目描述：

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

解法：

/**
 * 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 head(0); ListNode *cur = &head;
    int sum_or_carry = 0;
    while (l1 || l2 || sum_or_carry) {
        if (l1) {
            sum_or_carry += l1->val;
            l1 = l1->next;
        }
        if (l2) {
            sum_or_carry += l2->val;
            l2 = l2->next;
        }
        cur->next = new ListNode(sum_or_carry % 10);
        cur = cur->next;
        sum_or_carry /= 10;
    }
    return head.next;
    }
};