A Reliable Advanced Sudoku Scan Loop

Advanced solving is less about knowing every pattern than about asking the right question in a stable order.

This loop gives each technique a turn and tells you when to stop searching.

Reset with singles

After any major elimination, scan naked and hidden singles in the three changed units and then across the fullest board units. Many advanced moves are valuable because they return the puzzle to this stage.

Scan locked candidates

For each crowded box, ask whether a digit is confined to one line; for each crowded line, ask whether a digit is confined to one box. These short checks often outperform elaborate pattern hunting.

Compare pairs and triples

Look for exact candidate sets in units, then hidden digit sets. Keep the union or position count precise so an attractive near-pattern does not create an invalid elimination.

Choose one advanced family

If the loop is still empty, select a single-digit pattern such as X-Wing or a two-candidate pattern such as XY-Wing. Scan deliberately rather than mixing five half-remembered techniques.

Restart the loop after one move

Every elimination changes the evidence. Begin again from the local units instead of continuing the old search map. A loop is useful because it stays current.