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...Sudoku x moderate samples document by andrew stuart about this is a variant of the popular puzzle which contains two extra constraints on solution namely diagonals typically indicated grey cells in normal all rows columns and boxes must be filled with numbers to without repeating number there are nine every row column box containing sharing central grid cell also exactly solver can use information reduce possibilities those lines make deductions across board previously out reach however these allow compiler necessary clues thus creating balanced that rivals variety difficulty note it perfectly possible create co incidentally has unique each diagonal but unless revealed first usually no help strategies apply great com plete our puzzles expected rule proportion gentle should require little taking often solved eye balling techniques as grade increases contain much more important some basic illustrated after examples show how they extended pitfalls uniqueness do not always case guarantees ...