LeetCode Add Two Numbers

<pre name="code" class="cpp">

class Solution {public:    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {        ListNode *ans = new ListNode(-1);        ListNode *tail = ans;        int carry=0;        while (l1&&l2) {            int tmp=l1->val+l2->val+carry;            carry=tmp/10;            //尾插法插入。            tail->next=new ListNode(tmp%10);            tail=tail->next;            l1=l1->next;            l2=l2->next;        }        while (l1) {            int tmp=l1->val+carry;            carry=tmp/10;            tail->next=new ListNode(tmp%10);            tail=tail->next;            l1=l1->next;        }        while (l2) {            int tmp=l2->val+carry;            carry=tmp/10;            tail->next=new ListNode(tmp%10);            tail=tail->next;            l2=l2->next;        }        if (carry) {            tail->next=new ListNode(1);            tail=tail->next;        }        ans=ans->next;//去掉哨位节点        return ans;    }};