Sort by name a complex struct at c

Question

I am developing a c program. I am using this struct:

main.h:

#define LONG_CADENA 22
#define NUM_CADENAS 5
#define formato "%22s%22s%22s%22s%22s\n"
#define indi_format "%22s"

typedef struct Agenda
{
    char*          nom[NUM_CADENAS];
    struct Agenda* ant;
    struct Agenda* sig;
} ag;

I have this function to show the object Agenda:

#include <stdio.h>
#include "main.h"

ag* mostrarAgenda(ag* act)
{
    unsigned i = 0;
    void*    ini;

    ini = act;
    while (act++->sig)  //ma1: Reescribir esta línea utilizando el bucle for
    {
        for (; i<NUM_CADENAS; i++)
        {
            printf(indi_format, act->nom[i]);
        }
    }

    printf("\n");
    getchar();

    return ini;
}

I need change this function to sort the structs by one of the elements, for example by ag->nom[0]. But im starting with C, and I dont know how I could do it

Somebody could help me?

I know some sorting code, but I never use struct with pointers, and I dont know how apply a sorting code for this struct... — alberph, Jan 13 '14 at 12:28
@George: Using `qsort` is almost always better then implementing your own. — Klas Lindbäck, Jan 13 '14 at 12:30
@KlasLindbäck Yes, but as I can see he has an unknown length linked list of Agendas he wants to sort. Not that easy to use `qsort()` over that. — George, Jan 13 '14 at 12:49
@George `act++->sig` makes me think `act`is an array. Otherwise it wouldn't make sense to do `act++`. — Klas Lindbäck, Jan 13 '14 at 13:00
@KlasLindbäck It can be, but more likely the print function is not correctly implemented. — George, Jan 13 '14 at 13:07

George · Answer 1 · 2014-01-14T10:28:41.433

You can bubble sort it:

int c;
do {
    c=0;
    while(iterator->sig){
       if ( compare(iterator,iterator->sig) > 0 ) {
          swap(iterator,iterator->sig);
          c++;
       }
       iterator=iterator->sig;
    }
 } while (c);

You just have to implement the compare function, and the swap function.

Here the iterator is a pointer to the first element of the list initially. It is your duty to find it.

Also I would suggest in the print function to find the head of the list to start printing unless you are sure that the function is always passed the head of the list as parameter.

Sort by name a complex struct at c

1 Answers1