How to extract all combinations (unordered subsets) from a given set in C++?

Let us estimate the count before. Suppose N is the size of a given set, and K is the number of elements in the subset. The count of all combinations (unordered subsets) of size K is

Do not use static_cast when you cast from a basic class to a derived one. This may lead to undefined behavior. To handle the polymorphism, a virtual inheritance or a multiple inheritance case always use dynamic_cast instead.

The following short example shows the undefined behavior cases. This works with GCC, VC and online C++ shells:

Pros and cons

Why use Qt Test for unit testing and TDD (test-driven development)?

• small testing framework (about 6K lines of source code);
• seamless integration with QtCreator development environment;
• full support of Qt framework including classes/types and signal/slots;
• simple to start and use.

However, there are some drawbacks, too.