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Latest Changes and Additions

A quick list of the latest updates and additions to this site:

Killer Combinations
Date Created: Saturday 12-Apr-2008
Last Updated: Sunday 13-Apr-2014
Killer Sudoku Strategy. Killer Sudoku gives clues which are the sums of the solutions in defined cages. The combinations of possible cages based on the clue are listed here.

The Logic of Sudoku
Date Created: Friday 27-Feb-2009
Last Updated: Sunday 6-Apr-2014

What's New
Date Created: Monday 17-Aug-2009
Last Updated: Sunday 6-Apr-2014

A Set Theory Approach to Sudoku Strategies
Date Created: Thursday 20-Mar-2014
Last Updated: Sunday 30-Mar-2014
Sudoku, set theory, combinatorics, NP-complete, algorithmic efficiency

Strategy Families
Date Created: Saturday 12-Apr-2008
Last Updated: Sunday 30-Mar-2014
This is the index to the all the fully documented strategies used to solve Sudoku, Jigsaw Sudoku, Sudoku X and Killer Sudoku.

Unique Rectangles
Date Created: Friday 11-Apr-2008
Last Updated: Wednesday 5-Mar-2014
Sudoku Strategy. Unique Rectangles takes advantage of the fact that published Sudokus have only one solution. There are many formations and strategies based on this notion and are explained here.

Sword-Fish Strategy
Date Created: Friday 11-Apr-2008
Last Updated: Thursday 23-Jan-2014
Sudoku Strategy. Sword-Fish extends X-Wings into three rows and three columns. Candidate eliminations are possible where the cells that form the Sword-Fish are the only possible places for a solution on candidate N.

Innies and Outies
Date Created: Sunday 13-Apr-2008
Last Updated: Wednesday 15-Jan-2014
Killer Sudoku Strategy. An essential strategy for Killer Sudoku. It looks at the cells in cages which all inside or outside a unit or group of units. Since a unit must add up to 45 (in 9x9 Killer) overlaps can help remove candidates.

Cage Splitting
Date Created: Sunday 13-Apr-2008
Last Updated: Wednesday 15-Jan-2014
Killer Sudoku Strategy. Where a cage overlaps a unit, it can often be split giving new sub-cages with simpler combinations and often single cages with the solution for that cell.

Pattern Overlay
Date Created: Saturday 12-Apr-2008
Last Updated: Thursday 9-Jan-2014
Sudoku Strategy. Pattern Overlay Method, or POM, is a strategy that overlays all possible combinations of candidate X and finds out what remains.