character array in bubble sort

Question

I have written the following code to get sorted strings in a 2-D character array

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

void swap(char *,char *);

void main() {
    char a[20][20];
    int Pass = 0, i = 0, j = 0, n;

    printf("\nHow many elements you want to sort ? >> ");
    scanf("%d", &n);
    printf("\n\nEnter the elements to be sorted :\n");
    for (i = 0; i < n; i++)
        scanf("%s", a[i]);
    for (Pass = 1; Pass < n; Pass++) {
        for (j = 0; j < n - Pass; j++)
            if (strcmp(a[j], a[j + 1]) < 0)
                swap(a[j], a[j + 1]);
        printf("\n\nPass = %d\n", Pass);
        for (i = 0; i < n; i++)
            printf(" %s  ", a[i]);  
    }   
}

void swap(char *a, char *b) {
    char *t;
    *t = *a;
    *a = *b;
    *b = *t;
}

But, I get output as

How many elements you want to sort ? >> 5
Enter the elements to be sorted :
1 2 3 4 5
Pass = 1
2   3   4   5   1  
Pass = 2
3   4   5   2   1  
Pass = 3
4   5   3   2   1  
Pass = 4
Segmentation fault (core dumped)

Why do I encounter segmentation fault? (the same code works properly if I use an integer array instead of a character array)

Answer 1

Entry point main should be defined as

int main()

or (with arguments)

int main(int argc, char* argv[])

but may or may not return some value.

---

In function swap you are accessing uninitialized pointer which causes undefined behavior. There is no need to use pointer. Use plain char.

void swap(char *a,char *b)
{
    char t;
    t=*a;
    *a=*b;
    *b=t;
}

---

Also to avoid buffer overflow, you should tell scanf() how many characters to scan from input buffer

scanf("%19s",a[i]);

and check if scanning succeeded.

Now you should get correct results. Here is fixed code.