LeetCode 2. Add Two Numbers

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.Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)Output: 7 -> 0 -> 8

需要考虑的边界两个链表只有1个元素，且有进位。两个链表不等长。

/** * 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 *p=l1;        ListNode *q=l2;        ListNode *res=new ListNode(0);        ListNode *cur=res;        int carry=0;        while(p!=NULL||q!=NULL){            int x=(p!=NULL)?p->val:0;            int y=(q!=NULL)?q->val:0;            int sum=x+y+carry;            ListNode *tmp=new ListNode(sum%10);            carry=sum/10;            cur->next=tmp;            cur=cur->next;            if(p!=NULL) p=p->next;            if(q!=NULL) q=q->next;        }        if(carry>0){            cur->next=new ListNode(carry);        }        return res->next;    }};