CODEWITHSUNDEEP
carrayspointersquicksort
Martim Correia
Martim Correia

Reputation: 505

sorting an array of strings using qsort

So i have an array of strings called nova_str[50][1024] and what i want is to sort it using qsort the problem is that its not sorting anything.

My output:

* fcb
* bvb

Correct output:

* bvb
* fcb

as you can see the array isnt being sorted and i cant dont know why, so any help would be appreciated.

Program:

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


int string_cmp (const void * a, const void * b ) {
    const char * pa = *(const char * const * ) a;
    const char * pb = *(const char * const * ) b;

    return strcmp(pa,pb);
}

void print_array(char array[][1024], int len) 
{ 
    int i;
    for(i=0; i<len; i++)
    {
        printf("* %s\n",array[i]);
    }

}

int main(void)
{
    char nova_str[50][1024];
    strcpy(nova_str[0],"fcb");
    strcpy(nova_str[1],"bvb");
    qsort(nova_str,1, sizeof(char *)*1024, string_cmp);
    print_array(nova_str,2);
}

Upvotes: 1

Views: 1123

Answers (1)

bhristov
bhristov

Reputation: 3197

This will work. 

// You are getting a pointer from qsort, not a pointer to a pointer.
int string_cmp (const void * a, const void * b ) {
    const char * pa = (const char *) a;
    const char * pb = (const char *) b;

    return strcmp(pa,pb);
}

void print_array(char array[][1024], int len) 
{ 
    int i;
    for(i=0; i<len; i++)
    {
        printf("* %s\n",array[i]);
    }

}

int main(void)
{
    char nova_str[50][1024];
    strcpy(nova_str[0],"fcb");
    strcpy(nova_str[1],"bvb");
    // the size is 2, not 1
    // you also want the correct size of the elements
    // getting the size of the first element will ensure this
    qsort(nova_str,2, sizeof(nova_str[0]), string_cmp);
    print_array(nova_str,2);
}

I hope that this helps.

Upvotes: 4

Related Questions