Le tri n'est pas effectué

Question

Ce programme est une bibliothèque de livres fonctionnant par logiciel. Le problème est que lorsque je trier les livres par prix et les imprimer, ils ne sont jamais triés!

#include<stdio.h> 
#include<conio.h> 
#include<stdlib.h> 
static int count; 
struct book 
{ 
    int bookid; 
    char name[30]; 
    char author[30]; 
    float price; 
}; 
struct book b[40]; 
void add(void); 
void del(void); 
void sort(void); 
void price(void); 
void print(void); 
void main(void) 
{ 
    char choice; 
    while(1) 
    { 
     clrscr(); 
     printf("Enter a choice:\n 1.Add a book.\n 2.Delete a book.\n 3.Sort books by price.\n 4.To print all books details.\n 5.To print the names of the books whose price is less than 1000.\n 6.Exit\n"); 
     choice=getche();//doing by getch() as getche makes the program rough as it is printed 
     switch(choice) 
     { 
      case'1':add();break; 
      case'2':del();break; 
      case'3':sort();break; 
      case'4':print();break; 
      case'5':price();break; 
      case'6':exit(0); 
      default:printf("Enter a valid choice.");break; 
     } 
    }/*switch ends*/ 
} 
void add(void) 
{ 
    int i; 
    char ch[30]; 
    clrscr(); 
    for(i=count;i<40;i++) 
    { 
    printf("Enter books name:\n"); 
    gets(b[i].name); 
    printf("Enter author's name\n"); 
    gets(b[i].author); 
    printf("Enter price:\n"); 
    gets(ch); 
    b[i].price=atoi(ch); 
    b[i].bookid=count; 
    break; 
    } /* for ends*/ 
count++; 
printf("Dear User,the book has succesfully been added.The book id is %d",b[i].bookid); 


getch(); 
} 
void print(void) 
{ 
    int i; 
    clrscr(); 
    for(i=0;i<count;i++) 
    { 
     printf("Bookid=%d,Name=%s,Author=%s,Price=%f\n",b[i].bookid,b[i].name,b[i].author,b[i].price); 

    } 
getch(); 
} 

void del(void) 
{ 
    int i,j; 
    char ch[10]; 
    clrscr(); 
    printf("Enter book id:"); 
    gets(ch); // how do i put it into the structure as i dont know that which structure it belongs to 
    for(i=0;i<count;i++) //searching 
    { 
    if(b[i].bookid==atoi(ch)) 
     { 
      for(j=i;j<count;j++) 
      { 

       b[j]=b[j+1]; 
      }//for j ends 
     } //if ends 
    } /* for of i ends */ 
    count--; 
    // sort(); 
getch(); 
} 
//void del(void) 
//{ 

    // int i; 
    // char ch[10]; 
    // clrscr(); 
    //printf("Enter book id:"); 
     // gets(ch); 
     // for(i=0;i<40;i++) 
     // { 
    //  b[i]=b[i+1]; 
    // 
    // } 
    // count--; 
    // printf("Dear user,delete succesful"); 
//getch(); 
//} 
void sort(void) 
{ 
    int in,out; 
    struct book temp; 
    for(out=0;out<count-1;out++) 
    { 
     for(in=out+1;out<count;out++) 
     { 
      if(b[out].price>b[in].price) 
      { 
       temp=b[out] 
       b[out]=b[in]; 
       b[out]=temp; 
      } 
     }/*for out ends*/ 
    }//for in ends 
    printf("Dear user,the books are sorted by price.\n"); 

getch(); 
} 

void price(void) 
{ 
    int i; 
    clrscr(); 
    for(i=0;i<count;i++) 
    { 
     if(b[i].price<1000) 
     { 
     printf("%d.%s\n",i+1,b[i].name); 
     } 
    } 
getch(); 

Answer 1

temp=b[out] 
b[out]=b[in]; 
b[out]=temp; 

devrait probablement être:

temp=b[out]; 
b[out] = b[in]; 
b[in] = temp; 

Answer 2

Il ressemble à

for(in=out+1;out<count;out++) 

devrait être

for(in=out+1;out<count;in++) 

Answer 3

void sort(void) 
{ 
    int in,out; 
    struct book temp; 
    for(out=0;out<count-1;out++) 
    { 
     //**(in=out+1;out<count;out++)**//look here please 
     for(in=out+1;in<count;in++) 
     { 
      if(b[out].price>b[in].price) 
      { 
       temp=b[out] 
       b[out]=b[in]; 
       b[in]=temp;//**b[out]=temp;**//look here plz 
      } 
     }/*for out ends*/ 
    }//for in ends 
    printf("Dear user,the books are sorted by price.\n"); 

getch(); 
} 

Answer 4

La grosse erreur mise à part les erreurs n'utilise pas la fonction qsort de la bibliothèque C. À moins que vous n'écriviez un très bon tri (tri rapide, tri par fusion ou tri de tas selon vos besoins spécifiques), qsort sera meilleur et prendra moins de lignes de code.

Answer 5

Voici une correction testée (j'ai fait ceci afin que vous ayez un aperçu d'un bon code, je pense, et non pour faciliter vos devoirs: vous devez le comprendre et non le copier/coller). Pour votre problème, la fonction sort() est la plus importante.

#include <stdio.h> 

/** Types *************************************************************/ 

//You should introduce constants, to allow quick changes 
#define BOOK_NAME_LEN 30 
#define NAME_LEN 30 
#define PRICE_NUMBERS 4 

#define LIBRARY_CAPACITY 100 

//Allows to calculate ID numbers from library capacity (they're linked) 
#define STRINGIZE(a) #a 
#define STRINGIZE_CONSTANT(a) STRINGIZE(a) 
#define ID_NUMBERS (sizeof(STRINGIZE_CONSTANT(\ 
        LIBRARY_CAPACITY))/sizeof(char)-1) 

typedef struct book Book; 
struct book 
{ 
    //id is unsigned 
    size_t id; 
    char name[BOOK_NAME_LEN+1]; 
    char author[NAME_LEN+1]; 
    float price; 
}; 

typedef struct library Library; 
struct library { 
    Book books[LIBRARY_CAPACITY]; 
    size_t inventory; //Book count 
    size_t id_cnt; //ID counter, never decremented 
}; 

/** Input *************************************************************/ 

#include <string.h> 
#include <stdlib.h> 

//Purge stdin after removing ending \n 
void clean(const char *buffer, FILE *fp) 
{ 
    char *p = strchr(buffer,'\n'); 
    if (p != NULL) { 
     *p = 0; 
    } 
    else { 
     int c; 
     while ((c = fgetc(fp)) != '\n' && c != EOF); 
    } 
} 

//Gets a string from input without ending \n and 
//with stdin purge 
void get_str(char *str, size_t len) { 
    fgets(str, len+1, stdin); 
    clean(str, stdin); 
} 

//Explicit 
int get_int_num(size_t n_digits) { 
    int ret = 0; 

    //Converts an entered string to integer 
    char *num = malloc((n_digits+1)*sizeof(char)); 
    if(num !=NULL) { 
     get_str(num, n_digits); 
     ret = atoi(num); 
     free(num), num = NULL; 
    } 

    return ret; 
} 

//Explicit 
float get_float_num(size_t n_digits) { 
    float ret = 0.f; 

    //The comma is a char 
    char *num = malloc((n_digits+2)*sizeof(char)); 
    if(num !=NULL) { 
     get_str(num, n_digits+1); 
     ret = atof(num); 
     free(num), num = NULL; 
    } 

    return ret; 
} 

#include <math.h> 

//Gets an integer choice in a range, useful for menus 
int get_choice(int min, int max) { 
    int ret = 0; 
    do { 
     //The number of digits is deduced from 
     //max's one. 
     ret = get_int_num(log10(max)+1); 
    }while(ret < min || ret > max); 

    return ret; 
} 

/** Library functions **************************************************/ 

//Printing 
void print_library(Library const * const library) { 
    for(size_t i = 0 ; i < library->inventory ; ++i) { 
     printf("%u) %s BY %s : %.2f USD\n", i+1, library->books[i].name, 
              library->books[i].author, 
              library->books[i].price); 
    } 
} 

/* Adding */ 
void add(Library * const library) { 
    //Fills infos 
    printf("Name ? "); 
    get_str(library->books[library->inventory].name, BOOK_NAME_LEN); 
    printf("Author ? "); 
    get_str(library->books[library->inventory].author, NAME_LEN); 
    printf("Price (%u significative numbers) ? ", PRICE_NUMBERS); 
    library->books[library->inventory].price = get_float_num(PRICE_NUMBERS); 

    //Unique id from internal library counter 
    library->books[library->inventory].id = ++library->id_cnt; 
    //And finally increments books count 
    library->inventory++; 
} 
/* End adding */ 

/* Deleting */ 

#include <stdbool.h> 

//You will be able to remove by anything providing that you 
//search the corresponding ID (then, same menu as for sorting) 
bool remove_by_id(Library * const library, size_t id) { 
    bool ret = false; 

    for(size_t i = 0 ; i < library->inventory ; ++i) { 
     if(library->books[i].id == id) { 
      for(size_t j = i ; j < library->inventory-1 ; ++j) { 
       library->books[j] = library->books[j+1]; 
      } 
      library->inventory--; 

      ret = true; 
     } 
    } 

    return ret; 
} 

void del(Library * const library) { 
    printf("ID ? "); 
    size_t id = get_int_num(ID_NUMBERS); 

    printf("Book %u %s.", id, remove_by_id(library, id) ? 
             "successfully deleted" : 
          "NOT deleted (probably wrong id)"); 
} 
/* End deleting */ 

/* Sorting */ 
int cmp_by_price(void const *b1, void const *b2) { 
    return ((Book*)b1)->price >= ((Book*)b2)->price; 
} 

int cmp_by_author(void const *b1, void const *b2) { 
    return strcmp(((Book*)b1)->author, ((Book*)b2)->author); 
} 

int cmp_by_name(void const *b1, void const*b2) { 
    return strcmp(((Book*)b1)->name, ((Book*)b2)->name); 
} 

void sort(Library * const library) { 
    printf("Sort by :\n"); 
    printf("1) Book name\n"); 
    printf("2) Author name\n"); 
    printf("3) Price\n"); 
    printf("Your choice : "); 

    //Function pointer to use appropriate comparison function 
    int (*compare)(void const *, void const*) = NULL; 
    int choice = get_choice(1, 3); 
    switch(choice) { 
     case 3: 
      compare = cmp_by_price; 
      break; 
     case 2: 
      compare = cmp_by_author; 
      break; 
     case 1: 
      compare = cmp_by_name; 
      break; 
     default: 
      break; 
    } 

    qsort(library->books, library->inventory, sizeof(Book), compare); 

    printf("Sorted :\n"); 
    print_library(library); 
} 
/* End sorting */ 

/** Main program ******************************************************/ 

#include <ctype.h> 

bool stop() { 
    char c[1] = ""; 
    printf("\nContinue (\'y\' for yes) ? "); 
    get_str(c, 1); 

    return tolower(c[0]) != 'y'; 
} 

int main(void) { 
    //NEVER use global variables... Prefer to pass them through arguments 
    //(of course with pointers otherwise they won't be modified) 
    Library library = {{{0}}, 0, 0}; 

    do { 
     printf("Actions available : \n"); 
     printf("1) Add book\n"); 
     printf("2) Delete book\n"); 
     printf("3) Sort books\n"); 
     printf("Your choice : "); 

     int choice = get_choice(1, 3); 
     switch(choice) { 
      case 1: 
       add(&library); 
       break; 
      case 2: 
       del(&library); 
       break; 
      case 3: 
       sort(&library); 
       break; 
      default: 
       break; 
     } 
    }while(!stop()); 

    return 0; 
} 

Si vous ne comprenez pas quelque chose, nous sommes là pour vous aider à apprendre C après tout.