leetcode

0 class Solution {

1 static ListNode *rev(ListNode *list) {

2 ListNode *prev = nullptr, *next;

3 while (list) {

4 next = list->next;

5 list->next = prev;

6 prev = list;

7 list = next;

8 }

9 return prev;

10 }

11

12 public:

13 ListNode *doubleIt(ListNode *head) const {

14 head = rev(head);

15

16 ListNode *l = nullptr;

17 int carry = 0;

18 for (ListNode *p = head; p; l = p, p = p->next) {

19 const int val = p->val * 2 + carry;

20 p->val = val % 10;

21 carry = val / 10;

22 }

23

24 if (carry) l->next = new ListNode(carry);

25

26 return rev(head);

27 }

28 };