leetcode 2. Add Two Numbers

class Solution {public:ListNode* addTwoNumbers(ListNode* l1, ListNode* l2){int carry = 0;int val;ListNode *head = new ListNode(-1); // dummy headListNode *tail = head;while (l1 && l2){val = l1->val + l2->val + carry;if (val > 9){carry = 1;val -= 10;}else{carry = 0;}ListNode *p = new ListNode(val);tail->next = p;tail = p;l1 = l1->next;l2 = l2->next;}while (l1){val = l1->val + carry;if (val > 9){carry = 1;val -= 10;}else{carry = 0;}ListNode *p = new ListNode(val);tail->next = p;tail = p;l1 = l1->next;}while (l2){val = l2->val + carry;if (val > 9){carry = 1;val -= 10;}else{carry = 0;}ListNode *p = new ListNode(val);tail->next = p;tail = p;l2 = l2->next;}if (carry != 0){ListNode *p = new ListNode(1);tail->next = p;tail = p;}return head->next;}};