The files in the problem directory are c++ code that fails to build or run properly.
The first two letters of each filename are a logarithmic difficulty level

00 is elementary, usually syntax
10 is elementary but may include semantic bugs
20 a bug that can be tricky to find, subtle problems involving the linker
30 a bug that is runtime, and difficult
40 extremely difficult
50 unsolved

If the file is a directory, then the directory contains multiple files with a single problem.

All these files are assumed to be compiled using the command:

g++ -g -std=c++11

unless otherwise indicated.  The -g is for debugging