The fastest way (in terms of runtime) to program would be directly programming in machine code (which no human should ever do) or assembly (which you can do but i'd never recommend). These are relatively low level languages that are really hard to understand because don't provide the user with many functions and organization. For high level languages (C++, Java, Javascript, etc) I'd have to say it's either C++ or C, these have far less safety checks or garbage collection running. What makes code fast is how well it's written, and how well it manages loops. Poorly managed code will waste far more time than the language it's self.
