单链表List的C实现

头文件————————————————————————————————

//单链表的实现

#ifndef _LIST_H_

#define _LIST_H_



#include <stdlib.h>

#define Element int

struct node

{

     Element data;

     struct node *next;

};

typedef struct node* PtrToNode;

typedef PtrToNode Position;

typedef Position List;

List MakeEmpty(List L);

int IsEmpty(List L);

int IsLast(Position P, List L);

List CreateEmptyList();

Position Find(Element X, List L);

void Delete(Element X, List L);

Position FindPrevious(Element X, List L);//查找失败则返回链表的最后一个元素

void Insert(Element X, Position P, List L);//在P的后面插入新元素X

void PushBack(Element X, List L);

void PushFront(Element X, List L);

void DeleteList(List L);

Position Header(List L);

Position First(List L);

Position Advance(Position P, List L);//得到P的前一个位置

Element Retrieve(Position P);

#endif

　　

源文件——————————————————————————————————

//单链表的实现

#include "./List.h"

List MakeEmpty(List L)

{

     if (NULL == L)

          return L;

     Position p = First(L);

     Position tmp = p;

     while(NULL != p)

     {

          tmp = p->next;

          free(p);

          p = tmp;

     }

     L->next = NULL;

     return L;

}

int IsEmpty(List L)

{

     return First(L) == NULL;

}

int IsLast(Position P, List L)

{

     return P->next == NULL;

}

List CreateEmptyList()

{

     List L = (List)malloc(sizeof(struct node));

     if(NULL == L) return NULL;

     L->next = NULL;

     return L;

}

Position Find(Element X, List L)

{

     if(NULL == L) return NULL;

     Position p = First(L);

     while(NULL != p && p->data != X)

          p = p->next;

     return p;

}

void Delete(Element X, List L)

{

     if(NULL == L) return ;

     Position prev = FindPrevious(X, L);

     if(!IsLast(prev, L))

     {

          Position tmp = prev->next;

          prev->next = tmp->next;

          free(tmp);

     }

}

Position FindPrevious(Element X, List L)//查找失败则返回链表的最后一个元素

{

     if(NULL == L) return NULL;

     Position prev = Header(L);

     while(NULL != prev->next && X != prev->next->data)

          prev = prev->next;

     return prev;

}

void Insert(Element X, Position P, List L)//在P的后面插入新元素X

{

     if(NULL == L) return ;

     Position tmp = (Position)malloc(sizeof(struct node));

     if(NULL == tmp)     return ;

     tmp->data = X;

  　 tmp->next = P->next;
　　　P->next = tmp

}

void PushBack(Element X, List L)

{

     if(NULL == L) return ;

     Position pos = Header(L);

     while(NULL != pos->next)

          pos = pos->next;

     Position tmp = (Position)malloc(sizeof(struct node));

     if(NULL == tmp) return ;

     tmp->data = X;

     tmp->next = NULL;

     pos->next = tmp;

}

void PushFront(Element X, List L)

{

     if(NULL == L) return ;

     Position pos = L->next;

     Position tmp = (Position)malloc(sizeof(struct node));

     if(NULL == tmp) return ;

     tmp->data = X;

     tmp->next = pos;

     L->next = tmp;

}

void DeleteList(List L)

{

     MakeEmpty(L);

     free(L);

}

Position Header(List L)

{

     return L;

}

Position First(List L)

{

     if(NULL == L) return NULL;

     return L->next;

}

Position Advance(Position P, List L)//得到P的前一个位置

{

     if(NULL == L) return NULL;

     Position prev = Header(L);

     while(NULL != prev && prev->next != P)

          prev = prev->next;

     return prev;

}

Element Retrieve(Position P)

{

     return P->data;

}