leetcode

0 class Solution {

1 public:

2 ListNode *reverseKGroup(ListNode *head, int k) {

3 stack<ListNode *> st;

4 ListNode *tmp, *dummy, *next;

5

6 tmp = dummy = new ListNode(-1, nullptr);

7 for (ListNode *p = head; p; p = next) {

8 next = p->next;

9 st.push(p);

10 if (st.size() == k) {

11 while (!st.empty()) {

12 tmp = tmp->next = st.top();

13 st.pop();

14 }

15 tmp->next = next;

16 }

17 }

18 return dummy->next;

19 }

20 };