127.0.0.1: Created page with "An '''invalid''' or '''improper''' Sudoku does not have a unique solution, which means that it either has no solution at all or it has multiple solutions. A Sudoku wit..."

2021-10-27T11:37:15Z

Created page with "An '''invalid''' or '''improper''' Sudoku does not have a unique solution, which means that it either has no solution at all or it has multiple solutions. A Sudoku wit..."

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An '''invalid''' or '''improper''' [[Sudoku]] does not have a unique [[solution]], which means that it either has no solution at all or it has multiple solutions. A Sudoku with a unique solution is a [[valid]] Sudoku.

Invalid Sudokus are often the result of transcription errors, either by the maker, the publisher or a player. When a source frequently publishes invalid Sudokus, the generation process (manually or by computer) may be incorrect.

=== No Solution ===

There is little debate about Sudokus without any solution. At some point in the solving path, a [[contradiction]] will be found, which is not based on a prior assumption (see [[Trial & Error]]). From there, the puzzle can not be completed by the solver.

=== Multiple Solutions ===

When there are multiple solutions, a player who does not employ techniques that rely on a unique solution has the advantage. At some point, there are no further deductions that can be made, and the puzzle cannot be solved completely. A player who uses uniqueness-based techniques may draw the wrong conclusion from certain patterns, either resulting in a contradiction or the discovery of only one of the possible solutions.

== Computer Programs ==

When the contradiction is directly caused by two or more [[given]]s for the same [[digit]] in a single [[house]], most [[Sudoku Programs]] will not accept the puzzle. Programs which automatically verify each puzzle will also refuse puzzles that do not have a solution. Most programs will issue a warning when you load a puzzle that has multiple solutions.

However, [[eliminate|elimination]] of all [[candidate]]s in a [[cell]] or for a particular [[digit]] in a [[house]] may not always be detected or reported by a Sudoku Program.

Invalid - Revision history

127.0.0.1: Created page with "An '''invalid''' or '''improper''' Sudoku does not have a unique solution, which means that it either has no solution at all or it has multiple solutions. A Sudoku wit..."