Leetcode:reverse Nodes in K-group

The reverse of the list,

/** * Definition for singly-linked list. * struct ListNode {* int val; * ListNode *next; * ListNode (int x): Val (x), Next (NULL) {} *}; *//** * Definition for singly-linked list. * struct ListNode {* int val; * ListNode *next; * ListNode (int x): Val (x), Next (NULL) {} *};        */class Solution {public:listnode* Reversekgroup (listnode* head, int k) {if (!head | |!head->next | | k <= 1)    return head;    listnode* Pfirst = head;    listnode* Pbefore = NULL;    listnode* pkth = Pfirst;        while (1) {int cnt = k-1;            while (CNT && pkth) {pkth = pkth->next;        cnt--;        } if (cnt > 0 | | pkth = = NULL) break;        Reverse (pbefore,pfirst,pkth);        if (Pbefore = = NULL) head = Pfirst;        Pbefore = pkth;        Pfirst = pkth->next;    pkth = Pfirst;   } return head;    } void Reverse (listnode* pbefore, listnode*& Pfirst, listnode*& pkth) {listnode* p = pfirst;while (P! = pkth) {listnode* tmp = p->next;        P->next = pkth->next;        Pkth->next = p;    p = tmp;    } listnode* tmp = Pfirst;    Pfirst = pkth;      PKTH = tmp;   if (pbefore) Pbefore->next = Pfirst; }};

Leetcode:reverse Nodes in K-group