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;
}