题解 | #单链表的排序#

import java.util.*;

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

public class Solution {
    /**
     * 
     * @param head ListNode类 the head node
     * @return ListNode类
     */
    public ListNode sortInList (ListNode head) {
        // write code here
        if(head == null || head.next == null)
            return head;
        
        ListNode slow=head,fast=head.next;
        while(fast!=null&&fast.next!=null){
            slow=slow.next;
            fast=fast.next.next;
        }
        
        ListNode temp=slow.next;
        slow.next=null;//分割
        ListNode l=sortInList(head);
        ListNode r=sortInList(temp);
        
        ListNode newHead=new ListNode(-1);
        ListNode list=newHead;
        while(l!=null&&r!=null){
            if(l.val<r.val){
                list.next=l;
                l=l.next;
            }
            else{
                list.next=r;
                r=r.next;
            }
            list=list.next;
        }
        list.next = l != null ? l : r;
        return newHead.next;
    }
}