typedef struct Node
{
  int data;
  struct Node* next;
}node, *pLinkedList;

Node* removeMidNode(pLinkedList head)
{
  if (head->next == NULL || head == NULL)
    return head;
  if (head->next->next == NULL)
    return head->next;
  pLinkedList fast = head;
  pLinkedList slow = head;
  pLinkedList pre = NULL;
  /*
  head  1    2    3    4    5
  pre   slow  fast
  */
  //1个节点
  if (head->next->next == NULL)
    return head->next;
  while (fast->next != NULL && fast->next->next != NULL)
  {
    pre = slow;
    fast = fast->next->next;
    slow = slow->next;
  }
  //此时fast已到终点，slow为中间节点，pre为中间节点前一个节点
  pre->next = slow->next;
  free(slow);
  slow = NULL;
  return head;
}