using qsort to sort alphabetically strings of a 2d array

Question

how can i use qsort to sort alphabetically strings of a 2d array which has strings for a example if i have an array of 4 rows and every row has a string of >=50 characters ...how can i use the qsort function to sort string alphabetically ?

i used this

            qsort(arr, i, 500*sizeof(arr[0]), compare);
            for (j=0; j<i; j++) {
                    printf("%s\n",arr[j]);
            }

and the comparator i used is

            int compare (const void * a, const void * b ) {
                    return strcmp(a, b);
            }

but it gives me segmentation fault error while trying to compile

Are you sure it gives you a segmentation fault while trying to compile? It sounds like a compiler bug, which is unlikely. You probably encounter it during run time and not compile time — amit
– amit, Commented Dec 23, 2012 at 19:40
Should it not be return strcmp(*(char **)a, *(char **)b);? — user529758
– user529758, Commented Dec 23, 2012 at 19:40
i made a 2d array with strings and i try to sort them alphabetically with qsort command — user1809300
– user1809300, Commented Dec 23, 2012 at 19:41
@user1809300 We already know that. Tried what I proposed in my previous comment? — user529758
– user529758, Commented Dec 23, 2012 at 19:41

pbhd · Accepted Answer · 2012-12-23 20:07:23Z

4

This way it would work.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define size 10
int compare (const void * a, const void * b ) {
  return strcmp(*(char **)a, *(char **)b);
}
int main () {
    char *arr[size];
    char buf[1000];
    for (int i=0;i<size;i++) {
      arr[i]=strdup (gets (buf)); // using gets is risky because it can write past buf
    }
    qsort (arr, size, sizeof (char*), compare);
    for (int i=0;i<size;i++) {
      printf ("%s\n", arr[i]);
      free (arr[i]);
    }
}

answered Dec 23, 2012 at 20:07

pbhd

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1 Comment

pbhd Over a year ago

however, the idea of 2d arrays got lost. But was'nt clearly defined either.

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