Getting the input strings into an array and sort the array of strings alphabetically

Question

I want to input some strings and sort them alphabetically, at most 100 strings and the length of each string is less than 50, but I get a Segmentation fault.

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

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

int main()
{
    char sequences[100][50];
    int nr_of_strings;
    scanf("%d", &nr_of_strings);
    int i;
    for(i = 0; i < nr_of_strings; ++i)
        scanf("%s", sequences[i]);
    qsort(sequences, nr_of_strings, sizeof(char *), comp);
    for(i = 0; i < nr_of_strings; ++i)
        printf("%s\n", sequences[i]);
}

In your comp function, before you call strcmp, try to print the arguments, to see if they really are what you think they are. Or use a debugger. — piokuc
– piokuc, Commented May 23, 2013 at 9:26
Don't think you can do that with 2-D array. Think about creating array of char * for each string. — Rohan
– Rohan, Commented May 23, 2013 at 9:28

BLUEPIXY · Accepted Answer · 2013-05-23 09:42:16Z

3

change

return strcmp (*(const char **) a, *(const char **) b);
...
qsort(sequences, nr_of_strings, sizeof(char *), comp);

to

return strcmp ((const char *) a, (const char *) b);
...
qsort(sequences, nr_of_strings, sizeof(char [50]), comp);

answered May 23, 2013 at 9:42

BLUEPIXY

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3 Comments

jfly Over a year ago

Thanks for comment, I have tried this, still Segmentation fault.

BLUEPIXY Over a year ago

@jfly still Segmentation fault. Surely? It's work fine to me.

jfly Over a year ago

Sorry, I only change 'qsort(sequences, nr_of_strings, sizeof(char *), comp);' to 'qsort(sequences, nr_of_strings, sizeof(char [50]), comp);'. It works fine.

jfly · Accepted Answer · 2014-04-01 05:23:07Z

1

Try to declare the 2d array like this. It worked for me.

char** sequences;
int i;
sequences = (char**)malloc(100 * sizeof(char*));

for (i = 0; i < 100; i++)
{
    sequences[i] = (char*)malloc(50 * sizeof(char));
}

edited Apr 1, 2014 at 5:23

jfly

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answered May 23, 2013 at 9:40

user1819301

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