Teaching LinkedIn Queens #788: start with region scans on this 9×9 board. 9 regions, sizes 4–48. Walk students through 9 placements ending at R1C2, R2C5, R3C8, R4C3, R5C1, R6C4, R7C7, R8C9, R9C6.
Board spotlight: Several color regions span only a few cells — scan those regions first because they often force a queen into a single row or column. Region sizes range from 4 to 48 cells — smaller regions often pin a queen to a single row intersection.
Lesson step 1: show why R1C2 is forced. Region 2 only touches row 1 once on this board, so its queen must land at column 2. Ask: which rows/columns/regions are now closed?
Lesson step 2: show why R2C5 is forced. Region 3 only touches row 2 once on this board, so its queen must land at column 5. Ask: which rows/columns/regions are now closed?
Lesson step 3: show why R3C8 is forced. Region 4 only touches row 3 once on this board, so its queen must land at column 8. Ask: which rows/columns/regions are now closed?
Lesson step 4: show why R4C3 is forced. Row 4, column 3 is the forced queen once region 1, row, column, and touch rules are applied together. Ask: which rows/columns/regions are now closed?
Lesson step 5: show why R5C1 is forced. Region 5 only touches row 5 once on this board, so its queen must land at column 1. Ask: which rows/columns/regions are now closed?
Lesson step 6: show why R6C4 is forced. Region 6 only touches row 6 once on this board, so its queen must land at column 4. Ask: which rows/columns/regions are now closed?
Lesson step 7: show why R7C7 is forced. Region 8 only touches row 7 once on this board, so its queen must land at column 7. Ask: which rows/columns/regions are now closed?
Lesson step 8: show why R8C9 is forced. Region 7 only touches row 8 once on this board, so its queen must land at column 9. Ask: which rows/columns/regions are now closed?
Lesson step 9: show why R9C6 is forced. After eliminations, row 9 has one legal square left — column 6. Ask: which rows/columns/regions are now closed?
Recap: 9 queens, 9 regions, one solution path. Replay using region-first scanning.