C - sorting strings alphabetically without strcmp()

Question

I'm writing a small C programm that should sort comma separated strings alphabetically.

The input looks like this : "FSKT","EORD","OSEA","DA","ERTS","VG","FHR","EIAS","DOD"

This is the working code that does the sorting:

#include <stdio.h>
#include <string.h> 
int main() {
    char *a[] = {"FSKT","EORD","OSEA","DA","ERTS","VG","FHR","EIAS","DOD"};
    const char *s1,  *s2;
    int compRes,i,j;
    int length = 9;
    for (i = 0; i < length; i++) {
        for (j = i+1; j < length; j++){
            s1 = a[i];
            s2 = a[j];
            compRes = 0;
            while(*s1 && *s2){              
                if(*s1!=*s2){               
                    compRes = *s1 - *s2;     
                    break;                   
                }                           
                ++s1;
                ++s2;
            }
            if (compRes > 0 || (compRes == 0 && *s1)) {
                char* temp = a[i];
                a[i] = a[j];
                a[j] = temp;
            }
        }
        printf("%s ", a[i]);

    }
    printf("\n");
    return 0;
}

I'm not using strcmp() or something like that because it needs to stay very basic for later translation. Now i would like to use scanf() for the input string and if a dot is reached the input should stop. Somehow I'm already stuck at the input...

This is my attempt so far, unfortunately it isn't working.:

 #include <stdio.h>
    #include <string.h> 
    int main() {

        int compRes;
        int i;
        int j;
        int length = 9;
        char *s1;
        char*s2;
        char a[10][10] = { 0,0,0,0,0,0,0,0,0,0};

        //scan all strings separated with a comma

        scanf("%4[^,],%4[^,],%4[^,],%4[^,],%4[^,],%4[^,],%4[^,],%4[^,],%4[^,]" ,a[0],a[1],a[2],a[3],a[4],a[5],a[6],a[7],a[8]);



            for (i = 0; i < length; i++) {
                for (j = i+1; j < length; j++){
                    s1 = a[i];
                    s2 = a[j];
                    compRes = 0;
                    while(*s1 && *s2){
                        if(*s1!=*s2){
                            compRes = *s1 - *s2;
                            break;
                        }
                        ++s1;
                        ++s2;
                    }
                    if (compRes > 0 || (compRes == 0 && *s1)) {
                        char* temp = a[i];
                        a[i] = a[j];
                        a[j] = temp;
                    }

                }
                printf("%s ", a[i]);

            }
            printf("\n");
            return 0;
        }

Can someone help me?

Thanks in advance.

Answer 1

The problem is not in the scanning but in the following lines:

                char* temp = a[i];
                a[i] = a[j];
                a[j] = temp;

The previous code works fine for array of pointers and does not for a two dimensional array of chars. I would be surprised if it even compiles. You have basically two choices how to fix your program.

You can scan strings into a two dimensional array and setup correct pointers to your original one dimensional array of pointers and the program stays as before. I.e.:

    char b[10][10] = { 0,0,0,0,0,0,0,0,0,0};
    char *a[10];
    for(i=0; i<length; i++) a[i] = b[i];

Or you will need to copy whole strings when doing the exchange. I.e.:

               char temp[10];
               strcpy(temp, a[i]);
               strcpy(a[i], a[j]);
               strcpy(a[j], temp);