单链表ADT

#ifndef LIST_H
#define LIST_H

typedef char ElementType;

struct Node;
typedef struct Node *PtrToNode;
typedef PtrToNode Position;
typedef PtrToNode List;

List MakeEmpty(List L);
int IsLast(Position P, List L);
int IsEmpty(List L);
Position FindPrevious(List L, ElementType x);
Position Find(List L, ElementType x);
void Delete(List L, ElementType x);
void Insert(List L, ElementType x, Position P);
void PrintList(List L);
void DeleteList(List L);
void Reverse(List L);

#endif

#include"List.h"
#include<stdio.h>
#include<stdlib.h>
struct Node{
    ElementType Element;
    PtrToNode Next;
};

List MakeEmpty(List L)
{
    if(NULL != L)
    {
        L->Next = NULL;
    }
    return L;
}
/*L虽然没有使用，但是去掉L就破坏了我们的一个ADT的想法*/
int IsLast(Position P, List L)//L is unused
{
    return P->Next == NULL;
}

int IsEmpty(List L)
{
    return L->Next == NULL;
}
/*查找元素X的前驱*/
Position FindPrevious(List L, ElementType x)
{
    Position P;
    P = L;
    while(P->Next && P->Next->Element != x)
        P = P->Next;
    return u
/*Delete函数需配合FindPrevious，我们需要知道X的前驱才能进行删除*/
 void Delete(List L, ElementType x)
{
    Position Pre, Tmpcell;
    
    Pre = FindPrevious(L, x);//we need find the previous of deleted element
    if(!IsLast(Pre, L))
    {
        Tmpcell = Pre->Next;
        Pre->Next = Tmpcell->Next;
        free(Tmpcell);
    }
}

Position Find(List L, ElementType x)
{
    Position P;
    P = L;
    while(P && P->Element != x)
        P = P->Next;
    return P;
}
//we insert the element after the position p
void Insert(List L, ElementType x, Position P)
{
    Position TmpCell;
    TmpCell = (List)malloc(sizeof(struct Node));
    if(TmpCell == NULL)
        printf("Out of space!!!");

    else
    {
        TmpCell->Element = x;
        TmpCell->Next = P->Next;
        P->Next = TmpCell;
    }
}
void PrintList(List L)
{
    PtrToNode Tmp;
    Tmp = L->Next;
    while(Tmp->Next)
    {
        printf("%c-", Tmp->Element);
        Tmp = Tmp->Next;
    }
    printf("%c\n", Tmp->Element);
}

void DeleteList(List L)
{
    Position Tmp, P;
    P = L->Next;
    L->Next = NULL;
    while(P != NULL)
    {
        Tmp = P->Next;
        free(P);
        P = Tmp;
    }
    free(L);
}

void Reverse(List L)
{
    Position CurrentPos, NextPos, PreviousPos;
    
    CurrentPos = L->Next;//当前单链表的第一个节点
    PreviousPos = NULL;//指向新链表的第一个节点，假设开始为空
    while(CurrentPos != NULL)
    {
        NextPos = CurrentPos->Next;//取得当前节点的下一个节点位置
        CurrentPos->Next = PreviousPos;//当前节点连接成新的链表
        PreviousPos = CurrentPos;
        CurrentPos = NextPos;//遍历到下一个节点
    }
    L->Next = PreviousPos;//哑元节点连接新链表的头节点
}
//与上述思想差不多，主要在返回上
/*Asumming(假如）is no header and L is not empty*/
//List Reverse(List L)
//{
//    Position CurrentPos, NextPos, PreviousPos;
//    
//    CurrentPos = L;
//    PreviousPos = NULL;
//    while(CurrentPos != NULL)
//    {
//        NextPos = CurrentPos->Next;
//        CurrentPos->Next = PreviousPos;
//        PreviousPos = CurrentPos;
//        CurrentPos = NextPos;
//    }
//    return PreviousPos;
//}
//下面是复杂记忆写法，下面是我们经常写的一种方法，这样的代码不利于日后的记忆
//如果不经常用会很容易忘记，读者可以试着去自己写一遍
//void Reverse(List L)//含有头节点
//{
//    Position Tmp, P;
//    Tmp = L->Next;
//    L->Next = NULL;
//    while(Tmp != NULL)
//    {
//        P = Tmp->Next;
//        Tmp->Next = L->Next;
//        L->Next = Tmp;
//        Tmp = P;
//    }
//}
//List Reverse(List L)//不含头节点
//{
//    PtrToNode Tmp, P;
//    P = L;
//    L = NULL;
//    while(P != NULL){
//        Tmp = P->Next;
//        P->Next = L;
//        L = P;
//        P = Tmp;
//    }
//    return L;
//}

#include"SingleLinkedList.c"
#include<stdio.h>
#include<stdlib.h>

int main()
{
    List L;
    L = (List)malloc(sizeof(struct Node));
    if(NULL == L)
        printf("Allocation failure!!!");
    L = MakeEmpty(L);
    ElementType Elem;
    Position Last = L;
    printf("Please enter the element until the end of ‘#‘:");
    while((Elem = getchar()) != ‘#‘)
    {
        Position TmpCell;
        TmpCell = (List)malloc(sizeof(struct Node));
        if(NULL == TmpCell)
            printf("Allocation failure!!!");
        else
        {
            TmpCell->Element = Elem;
            TmpCell->Next = NULL;
            Last->Next = TmpCell;
            Last = TmpCell;
        }
    }
    PrintList(L);
    //删除并输出
    ElementType x;
    printf("Please enter the element you want to delete:");
    getchar();
    scanf("%c", &x);
    Delete(L, x);
    PrintList(L);
    //插入并输出
    Position Tmp;
    ElementType p, y;
    printf("After which element do you want to insert:");
    getchar();//消除回车字符
    scanf("%c", &p);
    printf("What element do you want to insert:");
    getchar();
    scanf("%c", &y);
    Tmp = Find(L, p);
    Insert(L, y, Tmp);
    PrintList(L);
    //将整个表倒置
    Reverse(L);
    printf("Now the reverse list is:");
    PrintList(L);
    //删除整个表
    DeleteList(L);
    return 0;
}