Sudoku Techniques

https://www.learn-sudoku.com/basic-techniques.html

https://www.learn-sudoku.com/advanced-techniques.html

Basic Techniques

1. Open Singles

   

2. Visual Elimination

3. Lone Singles

4. Locked Candidates

5. Hidden Single

   

   

6. Naked Pair

   

7. Naked Triplets & Quad in block

   

   

   They are the middle cell and the two cells on each end. Believe it or not, they make up a Naked Triplet. These cells must end up being the 5, 6, & 8, because together they share only those three candidates. The rule still applies - and you can safely remove 5, 6, & 8 from the other cells.

   

8. Hidden pairs

   A Hidden Pair is basically just a "buried" Naked Pair. It occurs when two pencil marks appear inexactly two cellswithin the same house (row, column, or block).

   This time, however, the pair is not "Naked" - it is buried (or hidden) among other pencil marks.

   

9. Hidden Triplets & Quads

   

Advanced Techniques

1. X-Wing

   

2. Swordfish

   Just as theX-Winginvolves two candidates in two columns or rows, the Swordfish involves three candidates in three columns or rows.

   

3. Finned swordfish

4. XY Wing

   

5. Unique Rectangle

   the logic it uses assumes the fact that the Sudoku puzzle you are working on hasonly one unique answer.

   This only works when four cells fall intoexactly two blocks.