Stateful Solvers and Iterators

Rust, yet again! Let’s take what we did last time with Solving Sudoku (again) and improve the code structure a bit more.


  • Create a ‘Solver’ struct that can maintain state (such as how many states we’ve visited, how much time we’ve spent)
  • Track the above stats
  • Turn the ‘Solver’ into an iterator which will iterate through given solutions (a single call will give the first solution or you can run through the iterator to get all of them)

If you’d like to follow along, I’ve started uploading the code here:


Solving Snakebird


A cute little puzzle game, where you move around snake(birds). Move any number of snakes around the level, eating fruit, and getting to the exit. The main gotchas are that you have gravity to content with–your snake will easily fall off the edge of the world–and each time you eat a fruit, your snake gets bigger. This can help get longer to get into hard to reach places or it can cause trouble when you trap yourself in corners.

Let’s use the new immutable.js solver to solve these problems!


Immutable.js Solvers

A bit ago I wrote about writing a generic brute force solver (wow, was that really two months ago?). It got … complicate. Mostly, because every time I wrote a step function, I had to be careful to undo the same. Wouldn’t it be nice if we could just write a step function and get backtracking for ‘free’?

Well, with immutability you can!