package com.blankj.hard._025;

import com.blankj.structure.ListNode;

/**

* <pre>

* author: Blankj

* blog : http://blankj.com

* time : 2017/10/16

* desc :

* </pre>

*/

public class Solution {

public ListNode reverseKGroup(ListNode head, int k) {

if (head == null || k == 1) return head;

ListNode node = new ListNode(0), pre = node;

node.next = head;

for (int i = 1; head != null; ++i) {

if (i % k == 0) {

pre = reverse(pre, head.next);

head = pre.next;

} else {

head = head.next;

}

}

return node.next;

}

private ListNode reverse(ListNode pre, ListNode next) {

ListNode head = pre.next;

ListNode move = head.next;

while (move != next) {

head.next = move.next;

move.next = pre.next;

pre.next = move;

move = head.next;

}

return head;

}

public static void main(String[] args) {

Solution solution = new Solution();

ListNode.print(solution.reverseKGroup(ListNode.createTestData("[1,2,3,4,5,6,7,8]"), 3));

}

}