链表冒泡排序

public ListNode sortList(ListNode head) {
        ListNode headpre=new ListNode();
        headpre.next=head;
        int length=0;
        while(head!=null){
            head=head.next;
            length++;
        }

        //冒泡
        for(int i=1;i<length;i++){
            int j=0;
            ListNode p0=headpre;
            ListNode p1=p0.next;
            ListNode p2=p1.next;
            while(p2!=null){
                reverse(p0,p1,p2);
                if(j==0){
                    headpre.next=p0.next;
                }
                j++;
                p0=p0.next;
                p1=p0.next;
                p2=p1.next;
            }
        }

        return headpre.next;
        
    }

    //三指针排序
    public void reverse(ListNode p0,ListNode p1,ListNode p2){
        if(p1.val>p2.val){
            p0.next=p2;
            p1.next=p2.next;
            p2.next=p1;
        }
    }