LeetCode之Reverse Nodes in k-Group

 /*本题方法类似与Swap Nodes in Pairs，直接遍历链表，先定位需要翻转的链表子段，然后将子段翻转即可。
 */
class Solution {
public:
    ListNode *reverseKGroup(ListNode *head, int k) {
        if(head == nullptr || head->next == nullptr || k < 2) return head;
        ListNode newHead(-1);
        newHead.next = head;
        ListNode *p(head->next), *q(head), *tmpHead(&newHead);
        int count(0);
        while(q != nullptr){
            q = q->next;
            if(++count == k){//该子段需要翻转，利用头插法即可
                ListNode *tail(tmpHead->next);
                while(p != q){
                    tail->next = p->next;
                    p->next = tmpHead->next;
                    tmpHead->next = p;
                    p = tail->next;
                }
                tmpHead = tail;
                if(q == nullptr) break;
                p = q->next;
                count = 0;
            }
        }
        return newHead.next;
    }
};