Juan Abadie whoan

## relation.php
// suppose `brothers` has a user_id foreign key

class User extends Model
{
    public function brothers() {
        return $this->hasMany('App\Brother');
    }
}

// bad way

## depth-first-search.cpp
class DFS {
  enum Method {
    PreOrder, InOrder, PostOrder
  } method;

  enum Direction {
    LeftToRight, RightToLeft
  } direction;

  template <typename TreeNode>
	// suppose `brothers` has a user_id foreign key

	class User extends Model
	{
	public function brothers() {
	return $this->hasMany('App\Brother');
	}
	}

	// bad way
	class DFS {
	enum Method {
	PreOrder, InOrder, PostOrder
	} method;

	enum Direction {
	LeftToRight, RightToLeft
	} direction;

	template <typename TreeNode>