LeetCode-Reverse Nodes in k-Group

 1 #include <iostream>
 2 using namespace std;
 3 
 4 ListNode *reverse(ListNode *head,ListNode *last_tail){ 
 5       ListNode *next_node=head->next;
 6       ListNode *res=head;
 7       
 8       while(next_node){
 9             ListNode *tmp=next_node->next;
10             next_node->next=head;
11             head=next_node;
12             next_node=tmp;
13       }
14       
15       last_tail->next=head;
16       return res;
17 }
18 
19 ListNode* reversekGroup(ListNode *head,int k){
20      ListNode *newHead=new ListNode(0);
21      newHead->next=head;
22      
23      int cnt=0;
24      ListNode *cur_node=head;
25      ListNode *last_tail=newHead;
26      while(cur_node){
27            cnt++;
28            if(cnt==k){
29                 ListNode *tmp=cur_node->next;
30                 cur_node->next=0;
31                 
32                 last_tail=reverse(last_tail->next,last_tail);
33                 last_tail->next=tmp;
34                 
35                 cnt=0;
36                 continue;
37            }
38            cur_node=cur_node->next;
39      }
40      return newHead->next;
41 }