leetcode---Add Two Numbers---链表

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

/** * 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)     {        if(l1 == NULL)            return l2;        if(l2 == NULL)            return l1;        ListNode *l = new ListNode(0);        ListNode *head = l;        int c = 0;        while(l1!=NULL && l2!=NULL)        {            int s = l1->val + l2->val + c;            ListNode *p = new ListNode(s%10);            c = s / 10;            l1 = l1->next;            l2 = l2->next;            l->next = p;            l = l->next;        }        while(l1!=NULL)        {            int s = l1->val + c;            ListNode *p = new ListNode(s%10);            c = s / 10;            l1 = l1->next;            l->next = p;            l = l->next;        }        while(l2!=NULL)        {            int s = l2->val + c;            ListNode *p = new ListNode(s%10);            c = s / 10;            l2 = l2->next;            l->next = p;            l = l->next;        }        if(c != 0)        {             ListNode *p = new ListNode(c);             l->next = p;        }        return head->next;    }};