Rooted: Created page with "The '''Hidden Single''' is a lot less sinister than its name suggests. In fact, most of the Sudokus published in newspapers and magazines can be solved by hidden singles..."

2020-05-31T05:10:22Z

Created page with "The '''Hidden Single''' is a lot less sinister than its name suggests. In fact, most of the Sudokus published in newspapers and magazines can be solved by hidden singles..."

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The '''Hidden Single''' is a lot less sinister than its name suggests.

In fact, most of the [[Sudoku]]s published in newspapers and magazines can be solved by hidden singles only. Together with the [[Naked Single]] it belongs to the [[single]]s, the most elementary [[solving technique]]s.

A '''Hidden Single''' is a single [[candidate]] remaining for a specific [[digit]] in a [[row]], [[column]] or [[box]]. In Sudoku variants, additional [[constraint]]s can also produce Hidden Singles.

An alternative term is '''Pinned Digit'''.

It may sound like a daunting task, checking 27 [[house]]s for each of the 9 digits, thus performing 243 checks, but most players do not check each of these combinations individually. Instead, they use techniques like [[Scanning]] and [[Cross-Hatching]] to locate the hidden singles.

== Example ==

The following example has a Hidden Single for [[digit]] 4 at the [[cell]] '''r6c5''' (row 6, column 5). This is the only cell with 4 as a [[candidate]] in the middle [[box]].

[[Image:HiddenSingle.png]]

Some [[Sudoku Helpers]], such as [[SudoCue]] and [[Simple Sudoku]], have the ability to highlight the cells for a chosen digit. Such highlighting makes Hidden Singles particularly obvious. The following is the same example [[grid]] with all cells having 4 as a candidate highlighted.

[[Image:HiddenSingle-Highlight.png]]

The six puzzles below can all be solved only using the placement of hidden singles.

1..2..3...2..1..4...3..5..67..6..5...5..8..7...8..4..18..7..4...3..6..2...9..2..7
..1...2.....3.4...5...6...1.5.1.2.7...8...4...2.9.7.8.9...7...8...5.9.....3...7..
1...2...3.4.....1...5.4.6.....2.1...7.8...1.5...4.8.....7.6.8...8.....2.4...3...7
1...2...3.4.....5....6.7.....5...8..7...8...2..6...9.....8.2....1.....6.2...7...1
1..2..3......4..5...6..7..82.....7...5..1..4...7.....98..1..2...6..2......4..6..7
...........12.34...235.617..35...74.....3.....76...82..143.825...87.23...........

== See also ==

* [[Naked Single]]

== External links ==

* [http://www.sudocue.net/guide.php#HiddenSingle Hidden Single] by ''[[User:Ruud|Ruud van der Werf]]''
* [http://homepages.cwi.nl/~aeb/games/sudoku/solving3.html Forced Digit] by ''Andries E. Brouwer''
* [http://www.angusj.com/sudoku/hints.php Hidden Single] by ''Angus Johnson''
* [http://www.brainbashers.com/sudokupinnedsquares.asp Pinned Square] by ''Kevin Stone''
* [http://www.sadmansoftware.com/sudoku/technique2.htm Hidden Single] by ''Simon Armstrong''
* [http://www.paulspages.co.uk/sudoku/howtosolve/#Stage2 Single-Sqaure Candidate] by ''Paul Stephens''
* [http://www.playr.co.uk/sudoku/solving.hiddensingle.php Hidden Single Number] by ''Gaby Vanhegan''
* [http://sudoku.awardspace.biz/solving_sudoku_basic.php?strategy=single%20position Single Position] by ''Vincent Tandart''
* [http://freewebs.com/experiencesudoku ExperienceSudoku] by ''Christopher Rucinski''

[[Category:Solving Techniques]]

Hidden Single - Revision history

Rooted: Created page with "The '''Hidden Single''' is a lot less sinister than its name suggests. In fact, most of the Sudokus published in newspapers and magazines can be solved by hidden singles..."