Linked List----press K nodes to reverse the list.

Title: Reverse the list by a group of K nodes.

Ideas:

By using the reverse of the inverted link list, the linked list is cycled, and the pointer continues to move forward when the count length k is not applied . When the count length reaches K, the group's endpoints First and node are passed in as parameters to the rollover function reverse and then re-stitched into the original linked list. Until the end of the list is reached.

The code is as follows:

/** * Definition for singly-linked list. * public class ListNode {* int val; * ListNode Next; * ListNode (int x) {* val = x; * Next = Null *} *} */public class Solution {public ListNode Reversekgroup (ListNode head, int k) {if (head = = null| | Head.next = = null| |                K<=1) return head;                ListNode Node=head; ListNode helper=new listnode (0);//Create an auxiliary head node; helper.next=head;//when the k> length of list returns to the original list; ListNode last         group=helper;//records the tail node of a set of nodes; ListNode nextgroup=head;//assists in recording the first node of the next set of nodes; ListNode first=nextgroup;//records the first node of the next set of nodes;        int count=1;                while (Node!=null) {if (count<k) {count++;            Node=node.next;                }else//count = = k;                {nextgroup=node.next;                Lastgroup.next=reverse (First,node);                Lastgroup=first;        First.next=nextgroup;        First=nextgroup;                                Node=first;            Count=1;            }} return helper.next;        }//String reversal general method, public ListNode reverse (listnode head,listnode tail) {ListNode pre=head;        ListNode Cur=head.next;        ListNode Ne=null;            while (Pre!=tail) {ne=cur.next;            Cur.next=pre;            Pre=cur;        Cur=ne;        } head.next=null;        Head=pre;    return head; }}

Linked List----press K nodes to reverse the list.