Category Archives: combinatorics

Check out my Sudoku solver

A couple days ago I started solving a few Sudokus. I would say I am average at solving them. I certainly don't use any advanced techniques and I don't really find the difficult ones very entertaining. By difficult here I mean where you have to think several moves ahead to rule out possibilities. So I […]


Counting Bijective, Injective, and Surjective Functions

In this post we'll give formulas for the number of bijective, injective, and surjective functions from one finite set to another. Although it's not difficult, a formula for the number of surjective functions was one of the first problems I solved as an undergrad that got me interested in recurrence relations and combinatorics. Let's use […]