25. Reverse Nodes in k-Group

ListNode* reverseKGroup(ListNode* head, int k) {
vector<int> temp;
while (head) {
temp.push_back(head->val);
head = head->next;
}
for (int i = k - 1; i < temp.size(); i += k) {
int j = 0;
while (j<k/2) {
swap(temp[i-j], temp[i - k + 1+j]);
j++;
}
}
ListNode* res = new ListNode(0);
ListNode** res1 = &res->next;
for (auto i : temp) {
res->next = new ListNode(i);
res = res->next;
}
return *res1;
}