第 17 章 高级数据表示（链表）

/*---------------------------------
    list.h -- 简单链表类型的头文件
---------------------------------*/

#ifndef LIST_H
#define LIST_H

#define TSIZE    45

typedef struct film
{
    char title[TSIZE];
    int rating;
} Item;

typedef struct node
{
    Item item;
    struct node *next;
} Node;

typedef struct list
{
    Node *head;                //指向链表头的指针
    unsigned int size;        //链表中的节点数
} List;


//初始化链表为空
void InitializeList(List *plist);

//确定链表是否为空，链表为空返回true，否则返回false
bool ListIsEmpty(const List *plist);

//确定链表是否已满
bool ListIsFull(const List *plist);

//确定链表中的节点数
unsigned int ListItemCount(const List *plist);

//在链表末尾添加项item，成功返回true，否则返回false
bool AddItem(Item item, List *plist);

//声明函数指针 PFUN，作为 Tranverse() 函数的第二形参
typedef void (*PFUN)(Item);

//把函数作用于链表的每一项
void Tranverse(const List *plist, PFUN pfun);

//释放已分配的内存
void EmptyTheList(List *plist);

#endif

/*---------------------------------------------
    list.c -- 简单链表接口实现
---------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include "list.h"

//把一项拷贝到节点中；CopyToNode 是辅助函数，不是接口函数
static void CopyToNode(Item item, Node *pnode)
{
    pnode->item = item;        //拷贝结构
}


//接口函数

void InitializeList(List *plist)
{
    plist->head = NULL;
    plist->size = 0;
}

bool ListIsEmpty(const List *plist)
{
    if (plist->head == NULL)
        return true;
    else
        return false;
}

bool ListIsFull(const List *plist)
{
    bool full;
    Node *pnode = (Node*)malloc(sizeof(Node));

    if (pnode == NULL)        //查看对内存是否已满，判断链表状态
        full = true;
    else
    {
        full = false;
        free(pnode);
    }

    return full;
}

unsigned int ListItemCount(const List *plist)
{
    return plist->size;
}

bool AddItem(Item item, List *plist)
{
    Node *pnew = (Node*)malloc(sizeof(Node));
    if (pnew == NULL) return false;

    CopyToNode(item, pnew);
    pnew->next = NULL;

    Node *pscan = plist->head;

    if (pscan == NULL)
        plist->head = pscan = pnew;
    else
    {
        while (pscan->next != NULL)
            pscan = pscan->next;

        pscan->next = pnew;
    }

    ++(plist->size);
    return true;
}

void Tranverse(const List *plist, PFUN pfun)
{
    Node *pnode = plist->head;        //指针的拷贝，不改变 plist->head 的值
    while (pnode != NULL)
    {
        (*pfun)(pnode->item);
        pnode = pnode->next;
    }
}

void EmptyTheList(List *plist)
{
    Node *ptmp;
    Node *pscan = plist->head;

    while (pscan != NULL)
    {
        ptmp = pscan->next;
        free(pscan);
        pscan = ptmp;
    }

    plist->head = NULL;        //销毁内存，头指针置为NULL
    plist->size = 0;        //销毁内存，节点数置为0
}

/*------------------------------------------------
    films3.c -- 使用抽象数据类型(ADT)风格的链表
------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>        //提供 exit() 原型
#include <string.h>
#include "list.h"

void showmovies(Item item);
char* s_gets(char *st, int n);

int main()
{
    List movies;
    Item temp;

    //初始化
    InitializeList(&movies);
    if (ListIsFull(&movies))
    {
        fprintf(stderr, "No memory available!
");
        exit(EXIT_FAILURE);
    }

    //获取用户输入并存储
    puts("Enter first movie title:");
    while (s_gets(temp.title, TSIZE) != NULL && temp.title[0] != '')
    {
        fputs("Enter your rating <0-10>:
", stdout);
        scanf("%d", &temp.rating);
        while (getchar() != '
') continue;

        if (AddItem(temp, &movies) == false)
        {
            fprintf(stderr, "Problem allocating memory
");
            break;
        }

        if (ListIsFull(&movies))
        {
            puts("The list is now full.");
            break;
        }

        puts("Enter next movie title (empty line to stop):");
    }

    //显示
    if (ListIsEmpty(&movies))
        printf("No data entered.
");
    else
    {
        printf("Here is the movie list:
");
        Tranverse(&movies, showmovies);
    }
    printf("You entered %d movies.
", ListItemCount(&movies));

    //清理
    EmptyTheList(&movies);
    printf("Bye!
");

    return 0;
}

void showmovies(Item item)
{
    printf("Movie: %s Rating: %d
", item.title, item.rating);
}

char* s_gets(char *st, int n)
{
    char *ret_val, *find;

    if (ret_val = fgets(st, n, stdin))
    {
        if (find = strchr(st, '
'))
            *find = '';
        else
            while (fgetc(stdin) != '
') continue;
    }

    return ret_val;
}