Building a "Mate-in-One" Chess Puzzle Solver from Scratch

Chess puzzles are incredibly addictive, but have you ever wondered how software instantly verifies if a move is a genuine checkmate?

While full chess engines like Stockfish look dozens of moves ahead using complex neural networks and alpha-beta pruning, writing an algorithm to detect a simple Mate-in-One is actually a fantastic, approachable exercise in graph theory and data modeling.

Here is a look at the exact step-by-step logic required to build a lightweight, fast mate-in-one puzzle detector.

1. Representing the Board: The FEN String

Before your code can calculate a move, it needs to understand the current state of the board. In computer chess, we use a standard string notation called FEN (Forsyth-Edwards Notation).