巨人航空公司的机群由座位容量为12的飞机组成。它每天飞行一个航班。按照下面的功能，写一个座位预订程序：
a．程序使用一个含12个结构的数组。每个结构要包括一个用于标识座位的编号、一个表示座位是否已分配出去的标记、座位预订人的姓和座位预订人的名。
b．程序显示下面的菜单：
To choose a function, enter its letter label:
a) Show number of empty seats
b) Show list of empty seats
c) Show alphabetical list of seats
d) Assign a customer to a seat assignment
e) Delete a seat assignment
f) Quit
c. 程序应能执行菜单所给出的功能。选择d）和e）需要额外的输入，每一个选项都应当允许用户终止输入。
d．执行完一个特定的功能之后，程序再次显示菜单，除非选择了f)。
e．每次运行程序都把数据保存到一个文件中。当程序再次运行时，首先从文件中载入数据（如果有的话）。
#include<stdio.h> #include<stdlib.h> #define MAX 12 void read_file(struct seat *p, char* filename); void choose(void); void show_number_empty(struct seat *p); void show_list_empty(struct seat *p); void show_list(struct seat *p); void assign_seat(struct seat *p); void delete_seat(struct seat *p); void write_file(struct seat *p, char* filename); struct seat{ int number; int assign; char lastname[10]; char firstname[10]; }; struct seat seats[MAX]={ //缺省设置 {101,0}, {102,0}, {103,0}, {104,0}, {105,0}, {106,0}, {107,0}, {108,0}, {109,0}, {110,0}, {111,0}, {112,0} }; int main(void) { read_file(seats, "seat.dat"); while( 1 ) choose(); return 0;//此句无用 } void read_file(struct seat *p, char* filename) { FILE * pseats; if ((pseats = fopen(filename, "rb")) == NULL) printf("Can't open %s file. So load default data.\n", filename); else { rewind(pseats); /* go to start of file */ while (fread(p, sizeof (struct seat), MAX, pseats) == 1) continue; fclose(pseats); printf("read %s successfully!\n", filename); } } void choose(void) { char command[10]; printf("\nTo 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 assignment\n"); printf("f) Quit\n"); gets(command); switch( command[0] ) { case 'a': show_number_empty(seats); break; case 'b': show_list_empty(seats); break; case 'c': show_list(seats); break; case 'd': assign_seat(seats); break; case 'e': delete_seat(seats); break; default : write_file(seats,"seat.dat"); puts("Quit"); exit(1); } } void show_number_empty(struct seat *p) { int i,n; for (i=0, n=0; i<MAX; i++) if ( p[i].assign == 0 ) n++; printf("There are %d empty seats\n",n); } void show_list_empty(struct seat *p) { int i; printf("empty seats:\n"); for (i=0; i<MAX; i++) if ( p[i].assign == 0 ) printf("number %d\n", p[i].number); } void show_list(struct seat *p) { int i; printf("seat list:\n"); for (i=0; i<MAX; i++) { printf("number %d\t", p[i].number); 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) { int number, i; printf("Input the seat number:"); scanf("%d", &number); getchar(); for (i=0; i<MAX; 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); getchar(); p[i].assign = 1; printf("assign NO.%d seat successfully!\n", p[i].number); } return; } printf("%d is a invalid seat number!\n", number); } void delete_seat(struct seat *p) { int number, i; printf("Input the seat number:"); scanf("%d", &number); getchar(); for (i=0; i<MAX; 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; } printf("%d is a invalid seat number\n", number); } void write_file(struct seat *p, char* filename) { FILE * pseats; if ((pseats = fopen(filename, "wb")) == NULL) { printf("Can't open %s file.", filename);//将文件以可写模式打开，没有则创造，清空文件内容 exit(1); } fwrite(p, sizeof (struct seat), MAX, pseats); fclose(pseats); }