2017-09-07 LeetCode_002 Add Two Numbers

2. Add Two Numbers

You are given two non-empty linked lists representing two non-negative integers. 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.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

Solution：

/**

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 *l3 = new ListNode(l1->val+l2->val), *p = l3;

13

        l1 = l1->next; l2 = l2->next;

14

        for (; l1 != NULL || l2 != NULL; l1 = (l1 == NULL ? NULL : l1->next), l2 = (l2 == NULL ? NULL : l2->next)) {

15

            int a = 0, b = 0;

16

            if (l1 != NULL) a = l1->val;

17

            if (l2 != NULL) b = l2->val;

18

            p->next = new ListNode(a+b+p->val/10);

19

            p->val %= 10;

20

            p = p->next;

21

        }

22

        if (p->val >= 10) {

23

            p->next = new ListNode(p->val/10);

24

            p->val %= 10;

25

        }

26

        return l3;

27

    }

28

};