Sudoku Variants
Samurai Star Inequality
Dec 8th
Samurai Star Inequality puzzle
I’m tempted to just say “good luck”, because frankly I think you’ll need it! Not of course in the literal sense, since this is an entirely logical problem, which requires absolutely no guess work, but in terms of finding the right areas to make progress quickly.
So having started at the end, let me introduce you to this Samurai Star Inequality puzzle. In all cases the “<” and “>” arrows point to the smaller number of each pair. Other than that it’s a regular Samurai Star – place 1 to 9 into each row, column and marked 3×3 box of each of the 5 underlying 9×9 grids (including the one in the centre).
And now back to the beginning: Good luck! 
Inequality Sudoku
Dec 4th
Inequality 2-grid Samurai Sudoku
Inequality jigsaw 6×6 Sudoku puzzle
On the Sudoku Xtra forums Marilyn suggested the great idea of an inequality Samurai puzzle for issue 2, so I’ve been having a look at doing this. And here’s the first result!
I’ve started off with a regular 6×6 jigsaw Sudoku, but have added inequalities, just to get you warmed up, then I’ve included my first ever Samurai Inequality Sudoku puzzle, albeit a 2-grid one for now.
You’ll notice in both puzzles here that I have included all inequality arrows, so you have far more information than you need – this is deliberate, to make them easier! On the 6×6 puzzle there are five really nice diamond shapes in the centre area, but in general I think having all the arrows is ugly (or lazy!) so I don’t plan to include them again in future (just as I’ve never included them in past published inequality/Futoshiki puzzles).
The rules of Inequality Sudoku are pretty simple – just place the numbers as you would in a regular Sudoku (or regular Jigsaw Sudoku in the 6×6 case), but obey the less-than (”<”) and greater-than (”>”) signs between squares. These indicate that the value of the number in a square is either less than or greater than its neighbour. And that’s it!
Good luck!
Stepping up – Three-away Sudoku!
Jul 21st
In a possibly inevitable next move (although in this case, I think, a probable conclusion to the theme rather than a stepping stone!) I thought I’d try out Three-away Sudoku, where black markers indicate all neighbouring squares with a difference of 3. With a 9×9 puzzle this still allows somewhat interesting 1-4-7, 2-5-8 and 3-6-9 chains to be used, although of course as you decrease the quantity of numbers that can fit in a chain so you start to lose the longer connected chains which I personally find so interesting.
Other than the three-away markers this is a regular 9×9 Sudoku puzzle, so just place 1 to 9 into each row, column and 3×3 box. Squares with a thick black bar between have a difference of 3 (e.g. 1&4), and those without a thick black bar between have a difference which is not 3.
An idea I have in mind to try next is to mix consecutive and two-away Sudoku in the same grid – I think any other combinations would be too confusing to play, although I suppose you could insert small numbers between squares to show selected differences which might make an interesting but possibly too mechanical variant. For me, I don’t want to have to stop and think about the rules I’m applying – in a good puzzle they should become intuitive really quickly (even if, in some cases, they are a little complex to learn they must become second nature for the puzzle to succeed – or so I find!).
Good luck!
Two-away Jigsaw 8×8
Jul 20th
Continuing with Two-away puzzles, I thought today I’d post a somewhat smaller challenge – an 8×8 Jigsaw Sudoku version.
The rules are pretty much what you’d imagine: place 1 to 8 into each row, column and bold-lined jigsaw piece. Numbers with a grey bar between them must have a difference of 2 (e.g. 1&3) and numbers without a grey bar between must have a difference that’s not 2. (This is important to ensure a unique solution!)
Good luck!
Two-away Samurai Jigsaw
Jul 17th
Two-away Samurai Jigsaw puzzle
Here’s a puzzle for the weekend – it’s a 5-grid samurai sudoku where in the corner grids a couple of the 3×3 regions have had their outlines tweaked to turn them into jigsaw sudoku puzzles, with full 8-way symmetry. There are very few givens, which means you’ll need to take full advantage of the two-away markers that are also in the grid. The grey rectangles indicate all neighbouring squares where the difference is 2 (e.g. 1&3 or 6&8) – even without precise values they can also be useful for quickly indicating where a chain of squares are all odd or all even.
Good luck!
Two-away Samurai Star
Jul 16th
I made this puzzle yesterday but then went and forgot to post it (oops) so I’m making up for that now! It’s a Samurai Star with two-away markers, just as per the previous two puzzles I posted.
Place 1 to 9 into each of the rows, columns and 3×3 boxes of the 5 underlying Sudoku grids (including the one in the centre), whilst obeying the two-away grey bars. Squares with a grey bar between have a difference of 2 (e.g. 1&3 or 2&4), and those without a grey bar have a difference which is not 2.
There are only 4 givens to get you going, so good luck!
Easy Two-away Sudoku
Jul 9th
I thought that yesterday’s puzzle wasn’t the best example of a new variant, so here’s an easier Two-away Sudoku puzzle. It has a few more connected squares which means the odd/even nature of the puzzle comes through a bit more clearly – if you’re familiar with consecutive sudoku then it probably won’t take you very long to solve.
The rules are as yesterday: place 1 to 9 into each row, column and 3×3 box, and then wherever a grey bar separates two squares the difference must be 2 – they must be “two-away” – and conversely where there is no grey bar then the difference is not 2.
Good luck!
Two-away Sudoku
Jul 8th
I just noticed that Monday marked my 50th post to garethmoore.co.uk, so to celebrate I thought I’d try a (slightly) new variation today: Two-away Sudoku. As its appearance might suggest, it is a close relative of Consecutive Sudoku. In fact it’s pretty much the same, except that the shaded grey bars indicate that the difference between neighbouring squares is 2 (not 1, as in Consecutive Sudoku). As in Consecutive Sudoku, all grey bars are drawn – so if one is absent then the difference is not 2.
For example, if you see a grey bar next to a square with ‘1′ in it then the neighbouring square must be ‘3′. However if you have a square with ‘1′ in and there is no grey bar between it and a neighbouring square then that square cannot contain ‘3′. It’s pretty simple really.
So – just place 1 to 9 into each row, column and 3×3 box whilst obeying the grey two-away markers!
Good luck!
Wrap-around Consecutive Samurai Star
Jul 6th
Wrap-around Consecutive Samurai Star puzzle
I seem to be posting more infrequently than I intend, so I thought I’d compensate with a puzzle that would take somewhat longer to complete! Here, then, is a wrap-around consecutive samurai star. All squares with consecutive values (a difference of 1) are marked with white bars, including those at opposite ends of rows and columns – wherever there isn’t a bar, the values are not consecutive.
The Sudoku logic takes a few twists here and there – in fact at one point near the end you will need to spot a particularly nasty hidden set in one region.
To solve the puzzle place 1 to 9 into each row, column and 3×3 box of each of the underlying 5 Sudoku grids (including the one in the centre). You’re only given 4 givens to get going, but with the consecutive information that’s all you need to find a unique solution.
Good luck!
Skyscraper Sudoku 8×8
Jun 19th
Continuing my series of 8×8 Skyscrapers and variants, here’s an 8×8 Sudoku with Skyscraper clues around the edge.
The rules are simple:
- Place 1 to 8 in each row, column and 4×2 box
- Obey the Skyscraper constraints: each number outside the grid reveals the number of ‘visible’ digits looking along that row/column, where higher digits obscure lower ones
Good luck!
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