List------Linked 链表

1、Definition

Linked list consists of a series of nodes. Each nodes contains the element and a pointer which points to the next node. The last node‘s next link points to NULL.

Linked=data+pointer

use the pointer to describe the logical relationship

2、Implementation

template<class List_entry>
class List
{
  public:
     List();
     int size();
     bool empty();
     bool full();
     ...
  protected:
     int count;
     Node<List_entry> *head;             //当声明一个linked时，只会拥有一个头指针
}

template<class List_entry>
struct Node
{
  List_entry entry;                            // data
  Node<List_entry> *next;               // point to the next node
  Node();
  Node(List_entry, Node<List_entry>*link=NULL);
}

3、Operations

(1)two types of insert

①在p节点所在位置插入

New(S)
 S->data=a;
 q->next=S;
 S->next=p;

②在p节点之后插入

New(S)
   S->data=a;
   S->next=p->next;
   p->next=S;

(2) create a linked list

In order to create a linked list, we have this algorithm

①To create a head

②To create new node S

③Insert S

void CreateList(Head)
{
   new(Head);
   Head->next=NULL;
   scanf("%c",ch);
   while(ch<>‘#‘)do
    {
       new(S);
       S->data=ch;
       S->next=Head->next;
       Head->next=S;
     }
}

上述构造方式为从头构造，在头元素出一个一个地插入

下面一种是从链尾增添

void CreateList(Head)
{
   new(Head);
   Head->next=NULL;
   Last=Head;
   scanf("%c",ch);
   while(ch<>‘#‘)do
   {
      new(S);
      S->data=ch;
      S->next=NULL;
      Last->next=S;
      Last=S;
    }
}

(3)insert an element at location i

Status ListInsert L(LinkList &L, int i, DataType e)
{
   LinkList p, s;
   p=L;
   int j=0;

   while(p&&j<i-1)
   {
      p=p->next;
      j++;
    }

   if(!p) return ERROR;
   s=(LinkList)malloc(sizeof(LNode));
   s->data=e;
   s->next=p->next;
   p->next=s;

   return OK;
}

(4)Delete

Status ListDelete(LinkList &L, int i)
{
   LinkList p, q;
   p=L;
   int j=0;

   while(p&&j<i-1)
   {
       p=p->next;
       j++;
    }

   if(!p) return ERROR;

    q=p->next;
    p->next=q->next;
    free(q);
}

(5)Search

①按位查找

Status ListSearch(LinkList &L, int i)
{
   LinkList p;
   int j=0;
   while(p&&j<i-1)
   {
      p=p->next;
      j++;
   }
   if(!p)return ERROR;
   e=p->next;
   return OK;
}

③按值查找

Status ListSearch(LinkList &L, DataType e)
{
   LinkList p;
   p=L;
   int j=0;
  while(p&&(p->next)!=e)
  {
         p=p->next;
         j++;
   }
   if(!p)
    {
        cout<<"Not found"<<endl;
        return ERROR;
    }
   else
    {
        return (j);
    }
}

3、circular linked list

4、Doubly linked list

(1)Insert

p->next=current->next;
p->prior=current;
current->next->prior=p;
current->next=p;

(2)Delete

current->next->prior=current->prior;
current->prior->next=current->next;