#define Error -1
#define OK   1
typedef int Status;

typedef int ElementType;

typedef struct Node{
   
   ElementType data;
   struct Node * next;
}Node, * LinkList;

//获得一个元素
Status GetElement(LinkList L, int i, ElementType *e){
 
   //指向第一个元素的值
   LinkList p = L->next;
   int j = 1;

   while (p && j < i) {
       p = p->next;
       j++;
   }
   
   if (!p || j > i) {
       return errno;
   }
   
   *e = p->data;
   return OK;
}

Status ListInsert(LinkList L, int i , ElementType e){

   LinkList p = L;
   
   for (int j = 1; j < i; j++) {
       p = p->next;
   }
   
   if (!p || i < 1) {
       return errno;
   }

   Node *node = (Node *)malloc(sizeof(Node));
   node->data = e;
   
   node->next = p->next;
   p->next = node;

   return OK;
};


//删除元素
Status listDeleteElement(LinkList L, int i, ElementType *e){
   LinkList p = L;
   for (int j = 1; j < i; j++) {
       p = p->next;
   }
   if (!p || !p->next || i < 1) {
       return errno;
   }
   Node *node = p->next;
   p->next = node->next;
   *e = node->data;
   free(node);
   return OK;
}

LinkList CreateListTail(LinkList p, int n){
   
   LinkList tempNode, L;
   
   
   p = (Node *)malloc(sizeof(Node));
   p->data = 9999;
   p->next = NULL;
   
   L = p;
   
   for (int i = 1; i <= n; i++) {
       tempNode = (Node *)malloc(sizeof(Node));
       tempNode->data = i;
       L->next = tempNode;
       
       L = tempNode;
   }
   
   L->next = NULL;
   
   return p;
}

void LogListNode(LinkList p){
   
   LinkList L = NULL;
   L = p->next;
   
   while (L) {
       printf("%d---",L->data);
       
       L = L->next;
       
   }
  
}

Status clearList(LinkList * L){
   
   LinkList p = (*L)->next;
   
   LinkList q = NULL;
   
   while (p) {
    q = p->next;
       free(p);
    p = q;
       
   }

   (*L)->next = NULL;
   
   return OK;
   
}
// 获得链表的最中间的节点的值
//利用快慢指针  慢指针每次1步， 快指针每次走两步，当快指针走到头时，慢指针就在中央

Status getListMidNode(LinkList p, ElementType *e){

   LinkList slow = p->next, quick=p->next;
   
   while (quick->next && quick) {
       
       quick = quick->next;
       
       if (quick->next) {
           quick = quick->next;
           slow = slow->next;
       }
   }
   
   *e = slow->data;
   
   return OK;
}