按照左右半区的方式重新组合单链表

public class Solution {
	/**
	 *	按照左右半区的方式重新组合单链表
	 *	输入：一个单链表的头节点head
	 *	将链表调整成题目要求的样子
	 *
	 *	后台的单链表节点类如下：
	 *
	 public class ListNode {
		int val;
		ListNode next = null;

		ListNode(int val) {
			this.val = val;
		}
	}
	 */
    public static void relocateList(ListNode head) {
        //1.快慢指针找到中间点
        ListNode hh = new ListNode(-1);//没分清“头部节点”的补救措施
        hh.next = head;
        ListNode l1,lmid,locate;//locate定位节点
        l1 = hh;
        lmid = hh;
        int length = 0;
        for(;l1.next!=null;l1 = l1.next){
            length++;
            if(length%2 == 0)
                lmid = lmid.next;
        }

        if(length > 3) {
            locate = lmid;
            lmid = lmid.next;//lmid及以后的都是R
            locate.next = null;
            l1 = hh.next;

            while (l1 != null) {
                locate = l1;
                l1 = l1.next;
                locate.next = lmid;
                locate = lmid;

                if (l1 != null) {
                    lmid = lmid.next;
                    locate.next = l1;
                }

            }
        }
    }
}