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;

    }

}

}

`