These are just a few old C++ projects from undergrad.
FourierTransform2D implements a 2D DFT and inverse DFT.
Icosahedron generates a 3D rendering of an icosahedron.
MBSet is a GUI for rendering the Mandelbrot set with a zoom feature.
RSA is a C++ implementation of the RSA algorithm.
ThreadsTransform2D is a multi-threaded version of FourierTransform2D.
Vector is just a from-scratch implementation of the basic features of std::vector.