This repo contains version of MPC in which state space was vastly reduced.
New state contains only a0..aN and delta0..deltaN. Constraints are very simple (-max..+max). There are no constraints for g(x) because there is no g(x).
New version of MPC is in file mpc_to_line/src/MPC.cpp. You can copmpare it with official solution (by Udacity) in mpc_to_line/solution/MPC.cpp.