[LeetCode] Add Two Numbers

ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {ListNode* sum = new ListNode(0);ListNode* pre = sum;if(l1 != NULL){pre->val += l1->val;l1 = l1->next;}if(l2 != NULL){pre->val += l2->val;l2 = l2->next;}int carry = 0;carry = pre->val/10;pre->val %= 10;while(l1 != NULL || l2 != NULL || carry != 0){ListNode* cur = new ListNode(0);pre->next = cur;if(l1 != NULL){cur->val += l1->val;l1 = l1->next;}if(l2 != NULL){cur->val += l2->val;l2 = l2->next;}cur->val += carry;carry = cur->val/10;cur->val %= 10;pre = cur;}return sum;}