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;

　C++style code

//C++style构建链表，有头结点
//operations
/*
LenList(L)链长
GetElem(i, e)换值
SearchElem(e, i)按值查找
InertElem(i, e)插值
DeleteElem(i) 删值
*/

template<typename Type>
struct Node
{
	Type data;
	Node<Type>*next;
};

template<typename Type>
class LinkList
{
public:
	LinkList()
	{
		head = new Node<Type>;
		head->next = NULL;
		len = 0;
		Type ch;
		Node<Type>*p;
		while (cin >> ch)
		{
			p = new Node<Type>;
			p->data = ch;
			p->next = head->next;
			head->next = p;
			len++;
		}
	}
	~LinkList()
	{
		Node<Type>*p = head;
		while (p->next)
		{
			DeleteElem();
		}
		delete head;
	}

	//LenList(L)链长
	int LenList()
	{
		return len;
	}

	//InertElem(e)从尾插值
	void InsertElem(Type e)
	{
		Node<Type>*p = head;
		while (p->next)
		{
			p = p->next;
		}

		Node<Type>*q = new Node<Type>;
		q->data = e;
		q->next = p->next;
		p->next = q;
		len++;
	}

	//InertElem(i, e)从第i位插值
	void InsertElem(int i, Type e)
	{
		Node<Type>*p = head;
		int j = 0;
		while (p->next && j<i - 1)
		{
			j++;
			p = p->next;
		}
		Node<Type>*q = new Node<Type>;
		q->data = e;
		q->next = p->next;
		p->next = q;
		len++;
	}

	//GetElem(i, e)换值
	void GetElem(int i, Type e)
	{
		int j = 0;
		Node<Type>*p = head;
		while (p->next && j<i - 1)
		{
			j++;
			p = p->next;
		}
		p->next->data = e;
	}

	//DeleteElem(i) 第i位删值
	void DeleteElem(int i)
	{
		int j = 0;
		Node<Type>*p = new Node;
		while (p->next && j<i - 1)
		{
			j++;
			p = p->next;
		}

		Node<Type>*q = p->next;
		p->next = q->next;
		delete q;

		len--;
	}

	//DeleteElem() 尾删值
	void DeleteElem()
	{
		Node<Type>*p = head;
		while (p->next->next)
		{
			p = p->next;
		}
		Node<Type>*q = p->next;
		p->next = q->next;
		delete q;
		len--;
	}

	//SearchElem(e)按值查找
	int SearchElem(Type e)
	{
		Node<Type>*p = head;
		int i = 0;
		while (p->next && p->data != e)
		{
			i++;
			p = p->next;
		}

		if (i == 0)
			return -1;
		else return i;
	}
	//SearchElem(i)按位查找
	Type SearchElem(int i)
	{
		Node<Type>*p = head;
		int j = 0;
		while (p->next && j<i)
		{
			j++;
			p = p->next;
		}
		return p->data;
	}

private:
	Node<Type>*head;
	int len;
};