C premier plus 第五版 结构和其他数据形式 14.18.9

这是典型的结构嵌套的使用。

//基于第八题的结构嵌套使用（四架飞机，每架相同的配置）。

#include<stdio.h>
#include<stdlib.h>
#define FLIGHT 4
#define SEAT 12

void read_file(struct flight *,char *);
void load_data(struct flight *);//默认数据。
int choose_flight(void);
int choose_command(struct flight *);
void write_file(struct flight *,char *);

void show_number_empty(struct seat *);
void show_list_empty(struct seat *);
void show_list(struct seat *);
void assign_seat(struct seat *);
void delete_seat(struct seat *);
void confirm_seat(struct seat *);

struct seat
{
	int number;
	int assign;
	char lastname[20];
	char firstname[20];
};

struct flight
{
	int number;
	struct seat seats[SEAT];//结构嵌套。
};

struct flight flights[4]=//初始化4个航班的结构数组。
{
	{102},
	{311},
	{444},
	{519}
};

int main(void)
{
	int n;
	read_file(flights,"seat.dat");
	while(1)
	{
		n=choose_flight();
		if(n<0 || n>=FLIGHT)//n=0123
			break;
		while(choose_command(&flights[n]))//返回是个1.这就是choose_command()函数返回值使int类型的原因。
			continue;
	}
	write_file(flights,"seat.dat");
	puts("Quit");

	return 0;
}

void read_file(struct flight *p,char *filename)//读取文件操作。
{
	FILE *pseats;
	if((pseats=fopen(filename,"r+b"))==NULL)
	{
		printf("Can't open %s file,So load default data.\n",filename);//首次打开时显示这一句，因为没有数据。也因此也不能有exit(1),否则会直接退出程序。
	    load_data(p);//载入默认的数据。使程序更友好。
	}
	else
	{
		rewind(pseats);//文件起始位置。
		while(fread(p,sizeof(struct flight),FLIGHT,pseats)==1)
			continue;
		fclose(pseats);
		printf("Read %s successfully!",filename);//第二次打开文件以后都会显示。
	}
}

void load_data(struct flight *p)//载入默认的数据。
{
	int i,j;
	for(i=0;i<FLIGHT;i++)
		for(j=0;j<SEAT;j++)
		{
			p[i].seats[j].number=i*100+j;
			p[i].seats[j].assign=0;
		}
}

int choose_flight(void)
{
	char command[10];
	printf("To choose a flight,enter lts letter label:\n");
	printf("a) Flights 102\t valid number is 000 001 002 003 004 005 006 007 008 009 010 011\n");
	printf("b) Flights 311\t valid number is 100 101 102 103 104 105 106 107 108 109 110 111\n");
	printf("c) Flights 444\t valid number is 200 201 202 203 204 205 206 207 208 209 210 211\n");
	printf("d) Flights 519\t valid number is 300 301 302 303 304 305 306 307 308 309 310 311\n");
	printf("e) Quit\n");
	gets(command);
	switch(command[0])//清楚了多余输入。
	{
	case 'a': return 0;//int 返回值函数值的原因。使n=0123
	case 'b': return 1;
	case 'c': return 2;
	case 'd': return 3;
	default: return 4;
	}
}

int choose_command(struct flight *p)
{
	char command[10];
	printf("Flight %d:\n",p->number);
	printf("To choose a function,enter its letter label:\n");
	printf("a) Show number of empty seats\n");
	printf("b) Show list of empty seats\n");
	printf("c) Show alphabetical list of seats\n");
	printf("d) Assign a customer to a seat assignment\n");
	printf("e) Delete a seat asignment\n");
	printf("f) Confirm a seat assignment\n");
	printf("g) Exit to the top-level menu\n");
	gets(command);
	switch(command[0])
	{
	case 'a': show_number_empty(p->seats);return 1;
	case 'b': show_list_empty(p->seats);return 1;
	case 'c': show_list(p->seats);return 1;
	case 'd': assign_seat(p->seats);return 1;
	case 'e': delete_seat(p->seats);return 1;
	case 'f': confirm_seat(p->seats);return 1;//注意p->seats的表达式的意义。
	default: return 0;
	}
}

void show_number_empty(struct seat *p)//显示空位的个数。
{
	int n=0,i;
	for(i=0;i<SEAT;i++)
		if(p[i].assign==0)
			n++;
	printf("There are %d empty seats.\n",n);
}

void show_list_empty(struct seat *p)//显示空位的标号信息。
{
	printf("Empty seats:\n");
	for(int i=0;i<SEAT;i++)
		if(p[i].assign==0)
			printf("Number %d\t%d\n",p[i].number,p[i].assign);
}

void show_list(struct seat *p)//显示位置的所有信息，number,assign,lastname,firstname。
{
	printf("Seat list:\n");
	for(int i=0;i<SEAT;i++)
	{
		printf("number %d \t assign %d\t",p[i].number,p[i].assign);
		if(p[i].assign==1)
			printf("Full %s %s\n",p[i].firstname,p[i].lastname);
		else
			printf("empty!\n");
	}
}

void assign_seat(struct seat *p)//预约座位。
{
	int number;
	printf("Input the seat number:");
	scanf("%d",&number);
	while(getchar()!='\n')
		continue;
	for(int i=0;i<SEAT;i++)
		if(p[i].number==number)
		{
			if(p[i].assign==1)
				printf("No! %d seat is already assigned!\n",p[i].number);
			else
			{
				printf("Input firstname of the holder:");
				scanf("%s",p[i].firstname);
				printf("Input lastname of the holder:");
				scanf("%s",p[i].lastname);
				while(getchar()!='\n')
					continue;
				p[i].assign=1;//订了位子计一。
				printf("assign No.%d seat successfully!\n",p[i].number);
			}
		    return ;//该句很重要，如果有符合的数字，那么就退出函数1，而不会打印出下一句无效的提示。
		}
		printf("%d is a invaild seat number!\n",number);
}

void delete_seat(struct seat *p)//删除定位。
{
	int number;
	printf("Input the seat number:");
	scanf("%d",&number);
	while(getchar()!='\n')
		continue;
	for(int i=0;i<SEAT;i++)
		if(p[i].number==number)
		{
			if(p[i].assign==0)
				printf("No.%d seat is already empty!\n",number);
			else
			{
				p[i].assign=0;
				printf("delete NO.%d seat successfully!\n",number);
			}
			return ;//功能如上。
		}
		printf("%d is a invalid seat number\n",number);
}

void confirm_seat(struct seat *p)//查询座位情况。
{
	int number,i;
	printf("Input the seat number:");
	scanf("%d",&number);
	while(getchar()!='\n')
		continue;
	for(i=0;i<SEAT;i++)
		if(p[i].number==number)
		{
			if(p[i].assign==0)
				printf("No.%d seat is empty!\n",number);
			else
				printf("No.%d seat is assigned! its holder is %s %s\n",p[i].firstname,p[i].lastname);
			return ;
		}
		printf("%d is a invalid seat number\n");
}

void write_file(struct flight *p,char *filename)//写入文件。
{
	FILE *pseats;
	if((pseats=fopen(filename,"w+b"))==NULL)//先清空文件“w+b”.
	{
		printf("Can't open %s filename",filename);
	    exit(EXIT_FAILURE);
	}
	fwrite(p,sizeof(struct flight),FLIGHT,pseats);
	fclose(pseats);
}

借鉴于原题例子。