测试题:
0. 相比起数组来说,单链表具有哪些优势呢?
答:长度非固定,可以申请添加长度
答案:对于数组来说,随机插入或者删除其中间的某一个元素,都是需要大量的移动操作,而单链表则完全没有这个问题。
数组插入图示:
单链表插入图示:
答:简单明了
答案:对于单链表来说,随机访问中间的某一个元素,都是需要大量的跳转操作(从第一个元素开始,然后通过指针一个一个往后跳,最后抵达目标位置),而数组则完全没有这个问题(直接通过下标索引值一步到位地访问)。.E
2. 现在要求编写一个记账小程序,那么你应该考虑使用数组还是单链表来存放数据呢?依据是什么?
答:使用单链表,依据是记账是可持续的,存储长度需要可调节
答案:应该使用单链表比较合适,因为记账小程序要求随时可以从中间位置插入数据,并且具有写入操作多(每天记一记),读取操作少(月底看下总结)的特点,所以选择单链表来实现会更合适。
3. 请问下面代码存在什么问题?
struct A
{
struct B b;
};
struct B
{
struct A a;
}
答:无限嵌套,死循环
答案:还是无限递归。
解析:在 A 结构体声明中定义 B 结构体,但在 B 结构体中又定义 A 结构体。
这就相当于当某人问你和你女朋友什么时候结婚,你们的回复都是“她/他说什么时候就什么时候,我绝对不会告诉你什么时候”酱紫……
4. 本节视频最后的代码演示中小甲鱼在写 releaseLibrary 函数的时候犯了一个比较明显的错误,你能找出来并改正吗?
答:看不出来(错误)
答案:
解析:
从逻辑上来说这是矛盾的:既然 library 指向的堆空间已经释放了,那么 library->next 理论上就是一个不存在的值,又何来 library = library->next; 呢?
应该这么改:
void releaseLibrary(struct Book *library)
{
struct Book *temp;
while (library != NULL)
{
temp = library;
library = library->next;
free(temp);
}
}
5. 请问下面代码中,为什么 addBook(struct Book **library) 函数要使用两个星号(**)?
#include <stdio.h>
#include <stdlib.h>
struct Book
{
char title[128];
char author[40];
struct Book *next;
};
void addBook(struct Book **library)
{
struct Book *book;
book = (struct Book *)malloc(sizeof(struct Book));
if (book == NULL)
{
printf("内存分配失败了!\n");
exit(1);
}
strcpy(book->title, "《零基础入门学习C语言》");
strcpy(book->author, "小甲鱼");
*library = book;
book->next = NULL;
}
int main(void)
{
struct Book *library = NULL;
addBook(&library);
return 0;
}
答:不理解(错误)
答案:这就是传值和传地的区别啦。
上面代码的内存存储结构如下:
但是,如果你把代码改成下面这样(一个星号):
#include <stdio.h>
#include <stdlib.h>
struct Book
{
char title[128];
char author[40];
struct Book *next;
};
void addBook(struct Book *library)
{
struct Book *book;
book = (struct Book *)malloc(sizeof(struct Book));
if (book == NULL)
{
printf("内存分配失败了!\n");
exit(1);
}
strcpy(book->title, "《零基础入门学习C语言》");
strcpy(book->author, "小甲鱼");
*library = book;
book->next = NULL;
}
int main(void)
{
struct Book *library = NULL;
addBook(library);
return 0;
}
那么,内存的存储结构就会变成:
看出区别来了吗?
addBook(library) 传递的是 library 指针的值,也就是把 NULL 传过去了;而 addBook(&library) 传递的是 library 指针的地址,自然,传过去的是指针的地址,那么要接住它就必须使用指向指针的指针(两个星号)啦~H
动动手:
0. 还记得上一节课后作业吗?
我们帮社区大妈编写了一个打疫苗的登记程序^o^Q
不过,那个只是实验品,因为它只能接受 3 个数据(小李、老王和法外狂徒张三)
这次,我们要求使用单链表来动态存储登记的数据(从堆中申请的空间记得在程序结束前要释放哦~)v
程序实现效果:
答:参考答案解答
#include <stdio.h>
#include <stdlib.h>
struct Date
{
int year;
int month;
int day;
};
struct Record
{
char name[16];
int age;
struct Date first;
struct Date second;
struct Record *next;
};
void getInput(struct Record *record)
{
char ch;
printf("请问姓名是:");
scanf("%s",record->name);
printf("请问年龄是:");
scanf("%d",&record->age);
printf("请问是否接种过疫苗(Y/N):");
getchar();
if(getchar() != 'Y')
{
record->first.year = 0;
printf("请尽快接种疫苗!\n");
}
else
{
printf("请输入第一针疫苗接种的日期(yyyy-mm-dd):");
scanf("%d-%d-%d",&record->first.year,&record->first.month,&record->first.day);
printf("请问是否接种第二针疫苗(Y/N):");
getchar();
if(getchar() != 'Y')
{
record->first.year = 0;
printf("请尽快接种第二针疫苗!\n");
}
else{
printf("请输入第二针疫苗接种的日期(yyyy-mm-dd):");
scanf("%d-%d-%d",&record->second.year,&record->second.month,&record->second.day);
}
}
printf("\n");
}
void printRecord(struct Record *head)
{
struct Record *record;
record = head;
while(record != NULL)
{
printf("姓名:%s",record->name);
printf("年龄:%d\n",record->age);
if(record->first.year == 1)
{
printf("第一针疫苗接种日期:%d-%d-%d\n",record->first.year,
record->first.month,record->first.day);
if(record->second.year == 1)
{
printf("第一针疫苗接种日期:%d-%d-%d\n",record->second.year,
record->second.month,record->second.day);
}
else
{
printf("未接种第二针疫苗!\n");
}
}
else
{
printf("未接种疫苗!\n");
}
record = record->next;
}
}
void addRecord(struct Record **head)
{
struct Record *record, *temp;
record = (struct Recoed *)malloc(sizeof(struct Record));
if(record == NULL)
{
printf("内存分配失败\n");
exit(1);
}
getInput(record);
if(*head != NULL)
{
temp = *head;
*head = record;
record->next = temp;
}
else
{
*head = record;
record->next = NULL;
}
}
void releaseRecord(struct Record *head)
{
struct Record *temp;
while(head != NULL)
{
temp = head;
head = head->next;
free(temp);
}
}
int main(void)
{
struct Record *record;
int i,ch;
while(1)
{
printf("是否需要录入(Y/N):");
do
{
ch = getchar();
}
while(ch != 'Y' && ch !='N');
if(ch == 'Y')
{
addRecord(&record);
}
else
{
break;
}
}
printf("请问是否需要打印已录入数据(Y/N):");
do
{
ch = getchar();
} while (ch != 'Y' && ch != 'N');
if (ch == 'Y')
{
printRecord(record);
}
releaseRecord(record);
return 0;
}
答案:
#include <stdio.h>
#include <stdlib.h>
struct Date
{
int year;
int month;
int day;
};
struct Record
{
char name[16];
int age;
struct Date first;
struct Date second;
struct Record *next;
};
void getInput(struct Record *record);
void printRecord(struct Record *head);
void addRecord(struct Record **head);
void releaseRecord(struct Record *head);
void getInput(struct Record *record)
{
printf("请问姓名是:");
scanf("%s", record->name);
printf("请问年龄是:");
scanf("%d", &record->age);
printf("请问是否接种过疫苗(Y/N):");
getchar();
if (getchar() != 'Y')
{
record->first.year = 0;
printf("请尽快接种疫苗!\n");
}
else
{
printf("请输入第一针疫苗接种的日期(yyyy-mm-dd):");
scanf("%d-%d-%d", &record->first.year, &record->first.month, &record->first.day);
printf("请问是否接种第二针疫苗(Y/N):");
getchar();
if (getchar() != 'Y')
{
record->second.year = 0;
printf("请尽快接种第二针疫苗!\n");
}
else
{
printf("请输入第二针疫苗接种的日期(yyyy-mm-dd):");
scanf("%d-%d-%d", &record->second.year, &record->second.month, &record->second.day);
}
}
putchar('\n');
}
void printRecord(struct Record *head)
{
struct Record *record;
record = head;
while (record != NULL)
{
printf("姓名:%s,年龄:%d\n", (*record).name, (*record).age);
if (record->first.year == 0)
{
printf("未接种疫苗!\n\n");
}
else
{
printf("第一针疫苗接种日期:%d-%d-%d,", (*record).first.year, (*record).first.month, (*record).first.day);
}
if ((*record).first.year != 0 && (*record).second.year == 0)
{
printf("未接种第二针疫苗!\n\n");
}
else if((*record).first.year != 0)
{
printf("第二针疫苗接种日期:%d-%d-%d\n\n", (*record).second.year, (*record).second.month, (*record).second.day);
}
record = record -> next;
}
}
void addRecord(struct Record **head)
{
struct Record *record, *temp;
record = (struct Record *)malloc(sizeof(struct Record));
if (record == NULL)
{
printf("内存分配失败!\n");
exit(1);
}
getInput(record);
if (*head != NULL)
{
temp = *head;
*head = record;
record->next = temp;
}
else
{
*head = record;
record->next = NULL;
}
}
void releaseRecord(struct Record *head)
{
struct Record *temp;
while (head != NULL)
{
temp = head;
head = head->next;
free(temp);
}
}
int main(void)
{
struct Record *head = NULL;
int ch;
while (1)
{
printf("请问是否需要录入(Y/N):");
do
{
ch = getchar();
} while (ch != 'Y' && ch != 'N');
if (ch == 'Y')
{
addRecord(&head);
}
else
{
break;
}
}
printf("请问是否需要打印已录入数据(Y/N):");
do
{
ch = getchar();
} while (ch != 'Y' && ch != 'N');
if (ch == 'Y')
{
printRecord(head);
}
releaseRecord(head);
return 0;
}