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Introducing Sudoku X read » You may have seen this puzzle in some newspapers, well it's now on sudoku.org.uk. I think it is an exciting and interesting variant giving the normal sudoku an extra twist. In a normal sudoku puzzle all rows, columns and 3x3 boxes must be filled with the numbers 1 to 9 without repeating a number. There are nine 'cells' in every row, column and box. In Sudoku X the two diagonals containing nine cells and sharing the central grid cell must also be filled with exactly 1 to 9. These are shaded in grey. The two diagonals are two extra constraints on the solution. The puzzle solver can use this information to reduce the possibilities in those lines and make deductions across the the board previously out of reach in a normal sudoku. However, these extra constraints allow the puzzle compiler to reduce the number of necessary clues thus creating a balanced puzzle that rivals normal sudoku in variety and difficulty. Note, it is perfectly possible to create a normal sudoku that co-incidentally has the unique 1 to 9 in each diagonal but unless this information is revealed first it is usually of no help to the solver. In Sudoku X all the normal sudoku strategies apply - and there are a great number of these. But to complete our puzzles the solver must be expected to use the extra diagonals. This rule is in proportion to the difficulty. Gentle puzzles should require little to no note taking and can often be solved with normal 'eye-balling' techniques. As the grade increases the diagonals contain much more important information. I have created a sample document [right click and save] you can freely download (and distribute). Some of the basic strategies are illustrated in the document and show how they can be extended to the diagonals. There are also two examples which show the pitfalls of Uniqueness strategies - and how they do not always apply in the case of Sudoku X. As with all our puzzles, I guarantees that there is exactly one solution. Unless explicitly stated they also have a logical solve route, although on the very hard ones this might be obscure to say the least. I have opened a thread for comments on this puzzle here Each month we will be producing a downloadable Pack of 50 Sudoku X puzzles. Click to see the ordering page. There are four grades in this mixed pack. Enjoy!  |
Puzzle Showcase? LOST IN THE PUZZLE MAZE? If you are looking for puzzles for your publication or an interactive puzzle for your website, then look no further -- your search ends with a click here. Michael Mepham Puzzle Showcase |
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