Method to find whether a String belongs to a Grammar or not

From a channel Lumen includes in full: Neso Academy posts structured, chalkboard-style university lecture series — theory of computation, digital electronics, operating systems, networks, C programming, discrete maths — numbered lesson by lesson with worked problems.

A 12-minute video from Neso Academy's catalogue; the title names its topic.

Video by Neso Academy, played through YouTube's embedded player.