Leetcode Add Two Numbers

class Solution {

public:

    ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {

        ListNode* p = l1;

        ListNode* q = l2;

        ListNode* ret = NULL;

        ListNode* ret_cur = NULL;

        int carry = 0;

        int digit = 0;

        while (p != NULL && q != NULL) {

            carry = add_node(p->val + q->val + carry, ret, ret_cur);

            p = p->next;

            q = q->next;

        }

        while (p != NULL) {

            carry = add_node(p->val + carry, ret, ret_cur); 

            p = p->next;

        }

        while (q != NULL) {

            carry = add_node(q->val + carry, ret, ret_cur); 

            q = q->next;

        }

        if (carry) add_node(1, ret, ret_cur);

        return ret;

    }   



    int add_node(int val, ListNode* &head, ListNode* &cur) {

        int carry = val / 10; 

        int digit = carry == 0 ? val : val - 10; 

        ListNode* cur_res = new ListNode(digit);

        if (head == NULL) {

            head = cur_res;

            cur = cur_res;

        } else {

            cur->next = cur_res;

            cur = cur_res;

        }

        return carry;

    }   

};

1発の水.
第2ラウンド:
You are given two linked lists representing two non-negative numbers. 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.
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)Output: 7 -> 0 -> 8
空のチェーンヘッダーを追加して、空の値の判断を簡略化します.

 1 /**

 2  * Definition for singly-linked list.

 3  * struct ListNode {

 4  *     int val;

 5  *     ListNode *next;

 6  *     ListNode(int x) : val(x), next(NULL) {}

 7  * };

 8  */

 9 class Solution {

10 public:

11     ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {

12         ListNode holder(0);

13         ListNode* prev = &holder;

14         

15         int carry = 0;

16         while (l1 != NULL && l2 != NULL) {

17             int sum = l1->val + l2->val + carry;

18             carry = sum / 10;

19             prev->next = new ListNode(sum % 10);

20             prev = prev->next;

21             l1 = l1->next;

22             l2 = l2->next;

23         }

24         

25         ListNode* last = (l1 == NULL) ? l2 : l1;

26         

27         while (last != NULL) {

28             int sum = last->val + carry;

29             carry = sum/10;

30             prev->next = new ListNode(sum % 10);

31             last = last->next;

32             prev = prev->next;

33         }

34         

35         if (carry) {

36             prev->next = new ListNode(1);

37         }

38         

39         return holder.next;

40     }

41 };