GridWits

Extended Unique Rectangles

Extreme Reference only

A Unique Rectangle's "deadly pattern" idea stretched across three rows, columns, and boxes instead of two, built around a locked triple of candidates.

The solver does not attempt this technique, so Smart Hint will never suggest it. It is documented because you may still want to spot it yourself.

A 1 B 2 C 3 D 4 E 5 F 6 G 7 H 8 I 9 1 2 3 1 2 3 1 2 3 1 2 3 7

How it works

  1. A1, D1, and G4 share a locked triple {1, 2, 3} across three rows, three columns, and three boxes — if the pattern's fourth cell, A7, were also purely {1, 2, 3}, the puzzle could complete more than one way by permuting the triple around it.
  2. A7 carries an extra candidate, 7 — so it can't be purely the triple. Eliminate 1, 2, and 3 from A7, leaving only 7.
  3. Not yet in GridWits' live solver — reference only.

Play a Sudoku that needs this technique →