  In this article, using the weighted discrete least-squares, we propose a
patch reconstruction finite element space with only one degree of freedom per
element. As the approximation space, it is applied to the discontinuous
Galerkin methods with the upwind scheme for the steady-state
convection-diffusion-reaction problems over polytopic meshes. The optimal error
estimates are provided in both diffusion-dominated and convection-dominated
regimes. Furthermore, several numerical experiments are presented to verify the
theoretical error estimates, and to well approximate boundary layers and/or
internal layers.
