Playing Wordle Using an Online Rollout Algorithm for Deterministic POMDPs.

In this paper, we consider an important class of Partially Observable Markov Decision Processes (POMDP) with unknown parameters, which contains the Wordle puzzle as a special case. For this class of POMDP, we develop a new on-line solution method, which is based on the rollout approach. Our method relies on the use of a base heuristic policy and guarantees cost improvement over that policy. When applied to Wordle, our algorithm solves the puzzle on-line. The performance is within 0.4% of the known optimal results, and is substantially better than that of the base heuristic policies we have tested.