题解 | #链表中的节点每k个一组翻转#

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 * }
 */

public class Solution {
    /**
     * 
     * @param head ListNode类 
     * @param k int整型 
     * @return ListNode类
     */
    public ListNode reverseKGroup (ListNode head, int k) {
        // write code here
        ListNode l = head;
        int length = 0;
        while(l != null){
            l = l.next;
            length++;
        }
        ListNode newHead = new ListNode(-1);
        newHead.next = head; 
        ListNode cur = head;
        ListNode pre = newHead;
        int c = length/k;
        while(c != 0){
           for(int i = 1;i < k;i ++){
            ListNode node = cur.next;
            cur.next = node.next;
            node.next = pre.next;
            pre.next = node;
        }
          pre = cur;
          cur = cur.next;
            c--;
        }
        
        return newHead.next;
    }
}