服了，好久没敲链表了，这都忘了

 newnode->next = cur->next;

cur->next = newnode;

 newnode->next = cur->next;

cur->next = newnode;

 newnode->next = cur->next;

cur->next = newnode;

 newnode->next = cur->next;

cur->next = newnode;

 newnode->next = cur->next;

cur->next = newnode;

 newnode->next = cur->next;

cur->next = newnode;

 newnode->next = cur->next;

cur->next = newnode;

 newnode->next = cur->next;

cur->next = newnode;

 newnode->next = cur->next;

cur->next = newnode;

 newnode->next = cur->next;

cur->next = newnode;

 newnode->next = cur->next;

cur->next = newnode;

 newnode->next = cur->next;

cur->next = newnode;

 newnode->next = cur->next;

cur->next = newnode;

 newnode->next = cur->next;

cur->next = newnode;