leetcode Add Two Numbers

加强基本功

class Solution {public:    ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {        ListNode *root = new ListNode(0);         ListNode *p = root;        int a = 0;        while(l1 || l2){            int v1 = (l1 ? l1->val : 0);            int v2 = (l2 ? l2->val : 0);            int tmp = v1 + v2 + a;            a = tmp /10;            ListNode *pNode = new ListNode(tmp%10);            p->next = pNode;            p = p->next;            if(l1) l1 = l1->next;            if(l2) l2 = l2->next;        }        if(a > 0){            ListNode *pNode = new ListNode(a);            p->next = pNode;        }        return root->next;    }};