Princeton’s Algorithms II course includes an assignment on finding Boggle words. Briefly, Boggle is a game where you have a two dimensional grid of random letters and players try to find as many real words as they can from the board by stringing together neighbouring letters.
This post looks at how tweaking the initial implementation can give a 2x speedup, but picking the right data structure gives a 4,200x speedup.
Code and a glass of wine 