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

pNode sortLinkedList(pNode head, int k)
{
  pNode sHead = NULL;//小頭
  pNode sTail = NULL;//小尾
  pNode eHead = NULL;//等頭
  pNode eTail = NULL;//等尾
  pNode bHead = NULL;//大頭
  pNode bTail = NULL;//大尾
  pNode temp = NULL;
  //拆分鏈表
  while (head != NULL)
  {
    temp = head->next;
    head->next = NULL;
    if (head->data < k)
    {
      if (!sHead){
        sHead = head;
        sTail = head;
      }
      else{
        sTail->next = head;
        sTail = head;
      }
    }
    else if (head->data == k)
    {
      if (!eHead){
        eHead = head;
        eTail = head;
      }
      else{
        eTail->next = head;
        eTail = head;
      }
    }
    else
    {
      if (!bHead){
        bHead = head;
        bTail = head;
      }
      else{
        bTail->next = head;
        bTail = head;
      }
    }
    head = temp;
  }
  //合并鏈表
  if (sTail)
  {
    sTail->next = eHead;
    eTail = (eTail == NULL ? sTail : eTail);
  }
  if (eTail)
  {
    eTail->next = bHead;
  }
  return sHead != NULL ? sHead : (eHead != NULL ? eHead : bHead);
}