分别用pnode bnode 存储小于和大于head链表 留下head  将排好序的链表与head拼接起来

class Solution {
    public ListNode quickSortList(ListNode head) {
        if(head==null||head.next==null) return head;
        ListNode bnode, pnode;
        bnode = null;
        pnode = null;
        while(head.next!=null){
            ListNode node = head.next;
            head.next = node.next;
            if(node.val<head.val){
                if(pnode==null){
                    pnode = node;
                    pnode.next = null;
                } else{
                    node.next = pnode;
                    pnode = node;
                }

            }
            if(node.val>=head.val){
                if(bnode==null){
                    bnode = node; 
                    bnode.next = null;
                }else{
                    node.next = bnode;
                    bnode = node; 
                }

            }

        }
        ListNode n1 = quickSortList(pnode);
        ListNode n2 = quickSortList(bnode);
        head.next = n2;
        if(n1!=null)getTail(n1).next = head;
        else return head;
        return n1;

    }

    public ListNode getTail(ListNode node){
        if(node==null||node.next==null) return node;
        return getTail(node.next);
    }
}