LeetCode 2 Add Two Numbers(链表)

题意：给出两个由链表表示的数的逆序形式，求和，并按照输入的形式给出链表头结点。

思路：链表基础题。

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