1+ /*
2+ Author: Andy, nkuwjg@gmail.com
3+ Date: Jan 18, 2015
4+ Problem: Reverse Nodes in k-Group
5+ Difficulty: Hard
6+ Source: https://oj.leetcode.com/problems/reverse-nodes-in-k-group/
7+ Notes:
8+ Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.
9+ If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is.
10+ You may not alter the values in the nodes, only nodes itself may be changed.
11+ Only constant memory is allowed.
12+ For example,
13+ Given this linked list: 1->2->3->4->5
14+ For k = 2, you should return: 2->1->4->3->5
15+ For k = 3, you should return: 3->2->1->4->5
16+
17+ Solution: ...
18+ */
19+
20+ /**
21+ * Definition for singly-linked list.
22+ * public class ListNode {
23+ * int val;
24+ * ListNode next;
25+ * ListNode(int x) {
26+ * val = x;
27+ * next = null;
28+ * }
29+ * }
30+ */
31+ public class Solution {
32+ public ListNode reverseKGroup (ListNode head ,int k ) {
33+ if (k <=1 )return head ;
34+ int T =GetLength (head ) /k ;
35+ ListNode dummy =new ListNode (0 ),cur =head ,ins =dummy ;
36+ dummy .next =head ;
37+ while ((T --) !=0 ) {
38+ for (int i =0 ;i <k -1 ; ++i ) {
39+ ListNode move =cur .next ;
40+ cur .next =move .next ;
41+ move .next =ins .next ;
42+ ins .next =move ;
43+ }
44+ ins =cur ;
45+ cur =cur .next ;
46+ }
47+ return dummy .next ;
48+ }
49+ public int GetLength (ListNode head ) {
50+ int length =0 ;
51+ while (head !=null ) {
52+ head =head .next ;
53+ length ++;
54+ }
55+ return length ;
56+ }
57+ }
