hackrank Sorting Array of Strings

https://www.hackerrank.com/challenges/sorting-array-of-strings/problem

int flag = 1;
int distinct_characters(const char* a);

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

if(strcmp(a, b) > 0){
    flag = 0;
}else flag = 1;
  
  return flag;
}

int lexicographic_sort_reverse(const char* a, const char* b) {
  if(strcmp(a, b) < 0){
      flag = 0;
  }else flag = 1;
  return flag;
}

int distinct_characters(const char* a){
    int dis_char = strlen(a);
    int len = strlen(a);
    for(int i = 0; i < len; i ++){
        if(a[i] != '\0'){
            for(int j = i + 1; j < len; j ++){
                if(a[i] == a[j]){
                    dis_char --;
                    break;
                } 
            }
        }
    }
    return dis_char;
}


int sort_by_number_of_distinct_characters(const char* a, const char* b) {
  int dis_a = distinct_characters(a);
  int dis_b = distinct_characters(b);
  if(dis_a > dis_b){
      flag = 0;
  }else if(dis_a == dis_b){
      if(strcmp(a, b) > 0){
          flag = 0;
      }else flag = 1;
  }else flag = 1;
   
 
  return flag;
}

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){
      flag = 0;
  }
  else if(len_a == len_b){
      if(strcmp(a, b) > 0){
          flag = 0;
      }else{
          flag = 1;
      }
  }else  flag = 1;
  return flag;
}

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