Here is my take on this.

int lexicographic_sort(const char* a, const char* b) {
    while (*(a) && *(b)) 
    {
        if(*a > *b) return 1;
        if(*a < *b) return -1;
        a++;
        b++;
    };
    if (*a) return 1;
    if (*b) return -1;
    
    return 0;
}

int lexicographic_sort_reverse(const char* a, const char* b) {
    while (*(a) && *(b)) 
    {
        if(*a > *b) return -1;
        if(*a < *b) return 1;
        a++;
        b++;
    };
    if (*a) return -1;
    if (*b) return 1;
    
    return 0;
}

int sort_by_number_of_distinct_characters(const char* a, const char* b) {
    int lena = strlen(a), lenb = strlen(b);
    char *arra = NULL, *arrb = NULL;
    char *arra_ad = NULL, *arrb_ad = NULL;
    int arra_sz = 0, arrb_sz = 0;
    const char *a_ad = a, *b_ad = b;


    arra = (char *)calloc(lena+1, sizeof(char));
    arrb = (char *)calloc(lenb+1, sizeof(char));
    arra_ad = arra;
    arrb_ad = arrb;

    while(*a || *b)
    {
        if (*a)
        {
            arra = arra_ad;

            while (*arra)
            {
                if(*a == *arra) goto founda;
                arra++;
            }
            arra_ad[arra_sz] = *a;
            arra_sz++;

            founda:;
            a++;
        }
        if (*b)
        {
            arrb = arrb_ad;

            while (*arrb)
            {
                if(*b == *arrb) goto foundb;
                arrb++;
            }
            arrb_ad[arrb_sz] = *b;
            arrb_sz++;

            foundb:;
            b++;
        }
    }

    free(arra_ad);
    free(arrb_ad);

    if(arra_sz > arrb_sz) return 1;
    if(arra_sz < arrb_sz) return -1;

    return lexicographic_sort(a_ad, b_ad);
}

int sort_by_length(const char* a, const char* b) {
    int lena = strlen(a), lenb = strlen(b);
    if (lena > lenb) return 1;
    if (lena < lenb) return -1;

    return lexicographic_sort(a, b);
}

void string_sort(char** arr,const int len,int (*cmp_func)(const char* a, const char* b)){
    char* temp = NULL;
    int i = 0, j = 0;

    for(i = len - 1; i > 0; i--)
    {
        for(j = 0; j < i; j++)
        {
            if (cmp_func(arr[j], arr[j+1])>0)
            {
                temp = arr[j+1];
                arr[j+1] = arr[j];
                arr[j] = temp;
            }
        }
    }
}

Here is Sorting Arrays of Strings solution in c - https://programmingoneonone.com/hackerrank-sorting-array-of-strings-solution-in-c.html

My submission

`

include

include

include

int lexicographic_sort(const char* a, const char* b) { if (a == NULL && b == NULL) return 0; // Both are NULL

if (a == NULL) return 1; 

if (b == NULL) return -1; 


// Handle empty strings
if (*a == '\0' && *b == '\0') return 0; 

if (*a == '\0') return 1;

if (*b == '\0') return -1; 

 while (*a != '\0' && *b != '\0') {

    if (*b < *a) {

        return -1; // a is less than b

    } else if (*b > *a) {

        return 1; // a is greater than b

    } 
    a++;

    b++;

}

// If we reach here, one of the strings is a prefix of the other

return (*b == '\0' && *a != '\0') ? -1 : (*b != '\0' && *a == '\0') ? 1 : 0;

}

int lexicographic_sort_reverse(const char* a, const char* b) {

int r = lexicographic_sort(a,b);
return r == -1? 1: r== 1 ? -1:0;
}

int count_distinct_characters(const char* str) {

int char_count[256] = {0}; // Assuming ASCII characters

int distinct_count = 0;


while (*str) {

    if (char_count[(unsigned char)*str] == 0) {

        distinct_count++;

    }

    char_count[(unsigned char)*str]++;

    str++;

}


return distinct_count;

}

int sort_by_number_of_distinct_characters(const char* a, const char* b) { if (a == NULL && b == NULL) return 0; // Both are NULL

if (a == NULL) return 1; 

if (b == NULL) return -1; 


// Handle empty strings

if (*a == '\0' && *b == '\0') return 0; 

if (*a == '\0') return 1;

if (*b == '\0') return -1; 

int distinct_a = count_distinct_characters(a);

int distinct_b = count_distinct_characters(b);


// Sort in ascending order of distinct character counts

return  distinct_b-distinct_a == 0 ? lexicographic_sort(a,b):distinct_b-distinct_a; // Returns negative if a < b, positive if a > b

}

int sort_by_length(const char* a, const char* b) { // Store original pointers const char* orig_a = a; const char* orig_b = b;

int len_a =0; int len_b = 0; for(; *a != 0; len_a++, *a++ ); for(; *b != 0; len_b++, *b++ );

if (len_a == len_b) return lexicographic_sort(orig_a, orig_b);

return len_b -len_a ;

}

void string_sort(char** arr,const int len,int (cmp_func)(const char a, const char* b)){

for (int i = 0; i < len ; i++) {

    int min_index = i; // Start with the current index as the minimum


    for (int j = i + 1; j < len; j++) {

        if (cmp_func( *(arr +min_index), *(arr +j)) <= -1) {
         min_index = j; // Update min_index if a smaller element is found

        }

    }


    // Swap the found minimum element with the first element

    if (min_index != i) {

        char* temp = *(arr +i);

      *(arr +i) = *(arr +min_index);

       *(arr +min_index) = temp;

    }

}

}

`

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

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

int sort_by_number_of_distinct_characters(const char* a, const char* b) { int count_a = 0, count_b = 0; int freq_a[26] = {0}, freq_b[26] = {0};

for (int i = 0; i < strlen(a); i++) {
    if (freq_a[a[i] - 'a'] == 0) {
        count_a++;
        freq_a[a[i] - 'a'] = 1;
    }
}

for (int i = 0; i < strlen(b); i++) {
    if (freq_b[b[i] - 'a'] == 0) {
        count_b++;
        freq_b[b[i] - 'a'] = 1;
    }
}

if (count_a == count_b) return strcmp(a, b); 
return count_a - count_b;

}

int sort_by_length(const char* a, const char* b) { int len_a = strlen(a); int len_b = strlen(b);

if (len_a == len_b) {
    return strcmp(a, b);
} else {
    return (len_a - len_b);
}

}

void string_sort(char** arr,const int len,int (cmp_func)(const char a, const char* b)){ // Bubble Sort for(int i = 0; i < len - 1; i++){ for(int j = 0; j < len - i - 1; j++){ if (cmp_func(arr[j], arr[j + 1]) > 0) { char* temp = arr[j]; arr[j] = arr[j + 1]; arr[j + 1] = temp; } } } }