（完整word版）CPrimerPlus第6版编程练习答案（已下载） 

C Primer Plus Sixth Edition Programming Exercise

Selected Answers

PE 14---8

/* pe14-8.c */

#include #include #include #include #define LEN 14 #define SEATS 12 #define EMPTY 0 #define TAKEN 1 #define CONTINUE 1 #define DONE 0 struct planestats

{ int seat_id; int status; char last[LEN]; char first[LEN];

}; int getmenu(void);

int getlet(const char *);

int openings(const struct planestats [], int); void show_empties(const struct planestats [], int); void list_assign(struct planestats *[], int); void assign_seat(struct planestats [], int); void delete_seat(struct planestats [], int); void

show_seats(const struct planestats [], int); void

sort(struct planestats *[], int); void makelist(const struct planestats [], char *, int); char * s_gets(char * st, int n);

int main(void) {

struct planestats plane_1[SEATS], *ps[SEATS]; int choice; int i; FILE *fp;

size_t size = sizeof(struct planestats);

for ( i = 0; i < SEATS; i++)

ps[i] = &plane_1[i]; if ((fp = fopen(\(i = 0; i < SEATS; i++) {

plane_1[i].status = EMPTY; plane_1[i].seat_id = i + 1; } else {

fread(plane_1, size, SEATS, fp); fclose(fp); } while ( (choice = getmenu() ) != 'q') {

switch (choice) {

case 'o': printf (\openings(plane_1, SEATS)); break;

case 'e': show_empties(plane_1, SEATS); break; case 'l': list_assign(ps, SEATS); break;

case 'a': assign_seat(plane_1, SEATS); break;

case 'd': delete_seat(plane_1, SEATS); break; default : puts(\trouble\

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C Primer Plus Sixth Edition Programming Exercise

Selected Answers

} } if((fp = fopen(\\to file.\

fwrite(plane_1, size, SEATS, fp); fclose(fp); }

puts(\return 0; }

#define CHOICES 6 int getmenu(void)

{ const char *descript[CHOICES] = { \seats\

\

\ \ \

\

const char labels[CHOICES + 1] = \int i;

puts(\for (i = 0; i < CHOICES; i++) printf(\labels[i], descript[i]); return getlet(labels); }

int getlet(const char * s) {

char c; c = getchar();

while (strchr(s, c) == NULL)

{ printf (\

list %s\\n\continue; c = getchar(); }

while (getchar() != '\\n') continue; return c; }

int openings(const struct planestats pl[], int n) { int count = 0; int seat; for (seat = 0; seat < n; seat++) if (pl[seat].status == EMPTY) count++; return count; }

void show_empties(const struct planestats pl[], int n) {

char seating[3* SEATS];

if ( openings(pl,n) == 0) puts(\else {

puts(\makelist(pl, seating, EMPTY); puts (seating) ; } }

void makelist(const struct planestats pl[], char * str, int kind) { int seat; char temp[LEN];

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C Primer Plus Sixth Edition Programming Exercise

Selected Answers

str[0] = '\\0';

for (seat = 0; seat < SEATS; seat++) if (pl[seat].status == kind) {

sprintf(temp,\strcat(str, temp); } }

void list_assign(struct planestats *ps[], int n) { int i;

if (openings(*ps, n) == SEATS) puts(\{ sort(ps, n); for(i = 0; i < SEATS; i++) if

( ps[i]->status == TAKEN ) printf (\

ps[i]->seat_id, ps[i]->last, ps[i]->first); }

} void assign_seat(struct planestats pl[], int n)

{ char list[3 *

SEATS]; int seat, loop;

if (openings(pl,n) == 0) puts(\else {

makelist(pl,list, EMPTY);

puts(\puts (list) ; do {

while( scanf(\

{ scanf(\);

puts(\puts (list) ; }

if (seat < 1 || seat > SEATS || pl[seat-1].status == TAKEN) {

puts(\puts (list) ; loop = CONTINUE;

} else loop = DONE; } while (loop == CONTINUE); while

(getchar() != '\\n') continue; puts(\first name:\puts(\LEN); printf(\pl[seat - 1].first, pl[seat - 1].last, seat);

puts(\if (getlet(\ {

pl[seat - 1].status = TAKEN; puts(\ } else

puts(\ } }

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C Primer Plus Sixth Edition Programming Exercise

Selected Answers

void delete_seat(struct planestats pl[], int n) { int seat, loop; char list[3 * SEATS];

if (openings(pl, n) == SEATS) puts(\

else { show_seats(pl, n); makelist(pl, list, TAKEN);

puts(\do {

while( scanf(\

{ scanf(\);

puts(\puts (list) ; }

if (seat < 1 || seat > SEATS || pl[seat-1].status == EMPTY) {

puts(\puts (list) ; loop = CONTINUE; } else loop = DONE; } while (loop == CONTINUE); while

(getchar() != '\\n') continue;

printf(\pl[seat - 1].first, pl[seat - 1].last, seat);

puts(\( getlet(\ {

pl[seat - 1].status = EMPTY; puts (\ } else

puts(\ } }

void show_seats(const struct planestats pl[], int n) { int i; puts(\currently taken:\i < SEATS; i++) if (pl[i].status == TAKEN)

printf(\pl[i].last, pl[i].first); }

void sort(struct planestats *array[], int limit) { int top, search; struct planestats * temp;

for (top = 0; top < limit -1; top++) for (search = top + 1; search < limit; search++) if

(strcmp(array[search]->last, array[top]->last) < 0) {

temp = array[search]; array[search] = array[top]; array[top] = temp; } }

49

C Primer Plus Sixth Edition Programming Exercise

Selected Answers

char * s_gets(char * st, int n) { char *

ret_val; char * find; ret_val = fgets(st, n, stdin); if (ret_val)

{ find = strchr(st, '\\n'); // look for newline if (find) // if the address is not NULL, *find = '\\0'; // place a null character there else

while (getchar() != '\\n')

continue; // dispose of rest of line }

return ret_val; }

PE 14---10

/* pe14-10.c */

/* the tricky part is declaring an array of pointers to functions */ #include

#include // for sqrt() double twice(double x); double half(double x); double thrice(double x); void showmenu(void); #define NUM 4 int main(void) {

double (*pf[NUM])(double) = {twice, half, thrice, sqrt}; double val; double ans; int sel;

printf(\(scanf(\

{ showmenu();

while (scanf(\ {

ans = (*pf[sel])(val); // first notation printf(\

ans = pf[sel](val); // alternative notation printf(\ }

printf(\ } puts(\return 0; }

void showmenu(void)

{ puts(\double the value 1) halve the value\

triple the value 3) squareroot the value\next number\

} double twice(double x) {return 2.0 * x;} double half(double x) {return x /

2.0;} double thrice(double x) {return 3.0 * x;}

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