链表排序

给一个无序的链表排序

//找链表的中间节点
public Node getmiddle(List l){
    if(l == null){
        return l;
    }
    Node fast = l;
    Node slow = l;
    //快指针走2步，慢指针走1步，快指针走到结尾时，慢指针刚好走到中间节点
    while(fast != null && fast.next != null){
        fast = fast.next.next;
        slow = slow.next;
    }
    return slow;
}
//排序、合并链表
public Node merge(Node left,Node right){
    Node tmp = new Node(0);
    Node thead = tmp;
    //从前向后遍历左右两部分链表，并进行排序合并
    while(left != null && right  != null){
        if(left.value < right.value){
            thead.next = left;
            left = left.next;
        }else{
            thead.next = right;
            right = right.next;
        }
        //如果左半部分还有剩余，将其链接到链表最后
        while(left != null){
            thead.next = left;
        }
        //如果右半部分还有剩余，将其链接到链表最后
        while(right != null){
            tmp.head = right;
        }
        return tmp.next;
    }
}
public void sortlist(List l){
    //找链表的中间节点
    Node mid = getmiddle(l);
    //将链表分开前后2部分
    Node right = mid.next;
    mid.next = null;
    //合并前后2部分的结果
    return merge(sortlist(l),sortlist(right));
}