题解 | #牛的品种排序IV#

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *新建一个链表遍历原链表，0 时采用头插法，1 采用尾插法
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    public ListNode sortCowsIV (ListNode head) {
       ListNode dummy = new ListNode(-1);
       ListNode tail = dummy;
     
       while(head != null){
            ListNode pre = dummy;
            if(head.val == 0){
                ListNode next = pre.next;
                pre.next = new ListNode(head.val);
                pre.next.next = next;
            } else {
                while(tail.next !=null){
                    tail = tail.next;
                }
                 tail.next = new ListNode(head.val);
                 tail = tail.next;
               
            }
            head = head.next;
       }
       return dummy.next;
    }
}