题解 | #链表中的节点每k个一组翻转#

/**
 * struct ListNode {
 *  int val;
 *  struct ListNode *next;
 * };
 */

class Solution {
  public:
    ListNode* reverseKGroup(ListNode* head, int k) {

        ListNode *tail = head;

        for (int i=0; i<k; i++) {
            if (tail== nullptr) {
                return head;
            }
            tail = tail->next;
        }

        ListNode *phead = nullptr;
        ListNode* cur = head;
        while (cur!=tail) {
            ListNode *temp = cur->next;
            cur->next = phead;
            phead = cur;
            cur = temp;
        }

        head->next = reverseKGroup(tail, k);

        return phead;
    }
};