题解 | #牛群分隔#

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
     *
     *
     * @param head ListNode类
     * @param x int整型
     * @return ListNode类
     */
    public ListNode cow_partition (ListNode head, int x) {
        // write code here
        if (head == null || head.next == null)
            return head;
        ListNode dummy1 = new ListNode(0);
        ListNode dummy2 = new ListNode(0);
        ListNode p1=dummy1;
        ListNode p2=dummy2;
        while (head != null) {
            if(head.val < x) {
                p1.next = head;
                p1 = p1.next;
                head=head.next;
                p1.next=null;
            }else{
                p2.next = head;
                p2 = p2.next;
                head=head.next;
                p2.next=null;
            }
        }
        p1.next = dummy2.next;
        return dummy1.next;
    }
}