LeetCode 25 Reverse Nodes in k-Group Add to List 划分list

package leetcode_50;


/***
 * 
 * @author pengfei_zheng
 * list划分为k组并且逆置
 */
public class Solution25 {
    public class ListNode {
         int val;
         ListNode next;
         ListNode(int x) { val = x; }
     }
    public ListNode reverseKGroup(ListNode head, int k) {
        ListNode curr = head;
        int count = 0;
        while (curr != null && count != k) { // find the k+1 node
            curr = curr.next;
            count++;
        }
        if (count == k) { // if k+1 node is found
            curr = reverseKGroup(curr, k); // reverse list with k+1 node as head
            // head - head-pointer to direct part, 
            // curr - head-pointer to reversed part;
            while (count-- > 0) { // reverse current k-group: 
                ListNode tmp = head.next; // tmp - next head in direct part
                head.next = curr; // preappending "direct" head to the reversed list 
                curr = head; // move head of reversed part to a new node
                head = tmp; // move "direct" head to the next node in direct part
            }
            head = curr;
        }
        return head;
    }
}