The Power of Symmetry by Felienne Hermans.
From the description:
This presentation by @Felienne presents programming problems, and how they can be solved efficiently and elegantly using symmetry.
The description is true but fails to capture the elegance of of Felienne’s presentation as she uses symmetry to dramatically reduce the number of states in classic programming problems.
Highly recommended if you need to “wow” a student or class with what is possible by looking just a bit deeper at a problem.