pub trait HashBuilder<T> {
  fn build(key: T) -> usize;
}

impl HashBuilder<usize> for usize {
  fn build(key: usize) -> usize {
    key % 10
  }
}

impl HashBuilder<String> for String {
  fn build(key: String) -> usize {
    return 24 as usize; // neglect the return here, it's just a dummy code
  }
}