Libraries in C++ for ACM (opens in new tab)

Aside from the author's habit of putting spaces after angle brackets and parenthesis, it's standard looking code. It's pretty busy looking, but then again, there's a lot going on:

- A generic type T is introduced into the scope of this member function.

- The template parameter MAXN is a compile time constant that is part of the type of the data structure.

- This is the count member function of the class BST, which is paramaterized on the types mentioned above.

- count does not modify any instance variables of BST.

- The parameter x is passed by constant reference.

- count's return type is int.

- The actual value returned is 1 if find(x) evaluates to true, and 0 if find(x) evaluates to false.

You learn to look for what you need to know when reading the code. Also, it's also worth noting that this code is most decidedly C++ only. C programmers may hate this code.

This is neither beautiful nor ugly. It is annoying.

I've been routinely programming in C++ for over a decade and this sort of required verbosity is what really rubs me the wrong way. This piece should really be:

  int BST<T, >::count(T & x)
  {
    return find(x) ? 1 : 0;
  }

When this is getting compiled, the template< class T, int MAXN > part can be unambiguously deduced from the context, so needing to type it is really a matter of helping a compiler do its job. MAXN is not used, so there's no need to drag it into the picture. Instead tell the compiler that BST can be specialized with more than one parameter by using trailing comma. The const-ness can and should be deduced automatically by looking at what find() is like, in a recursive fashion. If nothing in find() and the functions it calls modifies the x, then count() can accept const arguments and can be considered const itself.

I mean, c'mon. My car can park itself, but my compiler can't understand parametrized types without hand-holding :)

The code is fairly idiomatic C++, except maybe for the name of the class template (BST); hardly anybody names their classes in all capital letters (note that naming template parameters [T, MAXN in this case] in all capitals is quite common). Other than that, maybe the spaces after ( and < as well as before ) and > are a matter of taste.

I don't know.

What does find(x) do?

(Other than return something which evaluates in boolean context unless the template function is skipped for instantiation due to SFINAE and not modify x or *this unless a C-style or const_cast is used somewhere).

I don't think many C++ programmers think that much in the language counts as beautiful.

These are standard data structures and algorithms coded in C++. Pretty useful for programming competitions.

STL is allowed in all the competitions including TC, ICPC, SPOJ, etc BOOST is not allowed in any.

Prague and Shanghai (Igor, the author, was also at Shanghai)

Thanks. I'm glad you find them useful.

You can always bring codes in the form of printouts. And these libraries are mainly for practice problems on ACM UVA Online Judge.