Killer Sudoku
Killer Sudoku-X
Mar 4th
I wrote quite a lot yesterday about whether you “needed” the X in some Sudoku-X puzzles. I promised that I’d follow up with the result of analysing a stack of Killer Sudoku-X puzzles, and so here is that result.
I picked 64 Killer Sudoku-X puzzles (52 for the daily puzzlemix section plus 12 for the weekly puzzlemix section), and of those about 5 or 6 (I didn’t write it down…) could be solved via reasonable logical deduction without using the ‘X’ diagonals. So that’s roughly 10% of puzzles, if picked at random, that don’t need it. Quite a bit worse than regular Sudoku-X (see previous post), but nowhere near as high a percentage as I’d expected – I had thought it could be 50% or more, although I should say that this isn’t actually a fair comparison because I disabled the cleverest maths-solving techniques from my analysis software. So in fact this is comparing clever Sudoku-X solving against the same Sudoku-X solving with the addition of relatively less clever Killer Sudoku-X solving, so perhaps this biased the result much more to the non-Killer result (from yesterday) than it should have done. But anyway, I’m not writing a scientific paper and it’s good enough for me!
Killer Sudoku-X puzzleSo the result of all this is pretty simple: the Killer Sudoku-X on PuzzleMix for the coming year should be better than ever! You should need that X every time… 
PS Enjoy the Killer Sudoku-X I’ve attached here! Just place 1 to 9 in each row, column, 3×3 box and main diagonal, plus make sure the cages add to the given amounts – and don’t repeat a number in a cage.
Jigsaw Killer Sudoku
Mar 2nd
I’ve recently been working on refreshing the content for PuzzleMix.com, my play-online puzzle site, and one of the puzzle types I’ve been making is Killer Jigsaw Sudoku, where you not only have the jigsaw-shaped Killer regions but also jigsaw shapes instead of the regular 3×3 Sudoku boxes.
So I thought it would be a good idea to post one of these puzzles here – they can be quite tricky, at least until you get your head around the difference between these and regular Killer!
The rules are simple:
- Place 1 to 9 in each row, column and bold-lined region
- Place numbers in the dashed-line cages that add up to the given total for that cage
- No number can be repeated in a dashed-line cage
Good luck!
Double Toroidal Killer Sudoku Pro 8×8
May 13th
Double Toroidal Killer Sudoku Pro 8×8 puzzle
This puzzle certainly won’t be to everyone’s tastes, but it’s a double toroidal killer sudoku pro. Why double? Because there are toroidal jigsaw-shaped Sudoku regions, and there are toroidal jigsaw-shaped Killer Sudoku Pro cages. In other words, some of them wrap around the edges of the puzzle. It’s also an 8×8 puzzle, just to keep the Killer Sudoku (Pro!) logic fresh.
The rules are as you might expect:
- Place 1 to 8 into each row, column and bold-lined shape – some of these shapes are toroidal, so wrap from the end of one row/column to the opposite end of the same row/column
- Place numbers into the dashed-line Killer Sudoku Pro cages so that when the given operation is applied the result is the stated number. For ‘-’ operations start with the highest number.
- Numbers can’t repeat in dashed-line cages, and some cages (just one in this puzzle actually) are toroidal, so wrap around the rows/columns as described above
And that’s it! Good luck!
Hints: As always with this sort of puzzle, if you shade in the 8 bold-lined regions first with different colours you’ll find it much easier to keep track of what you’re doing. Also, all of the regions (both killer cages and bold-lined regions) have rotational symmetry order 4 – in other words, the same pattern repeats 4 times; this might help!
Toroidal Killer Sudoku 10×10
May 12th
Toroidal Killer Sudoku 10×10 puzzle
So far all of the “pure Sudoku logic” in my puzzles posted here has been pretty gentle. Well I decided that it was time to change that, but of course I wasn’t about to do that with a common garden puzzle! So I’ve applied some harder logic to this 10×10 Killer Sudoku with toroidal cages.
Because this is a 10×10 puzzle I’ve kept the Killer Sudoku part very easy – there are plenty of single cages (with apologies to those who dislike these!) and although the maths goes a tiny bit higher the actual ‘Killer reasoning’ is straightforward. But the Sudoku reasoning itself is definitely tougher, in places.
So here are the rules:
- Place 1 to 10 into each row, column and bold-lined 5×2 cage
- Place numbers so that they add up to the total at the top-left of each dashed-line cage
- Numbers may not repeat within a dashed-line cage
- Some cages wrap around the edges of the puzzle – they continue in the same row/column on the opposite side of the puzzle (so a cage leaving off the right of row 3 continues on the left edge of row 3, and vice-versa)
In summary, then, there are a few relatively unusual things here: the 1-10 Killer sums and 1-10 Sudoku; the toroidal cages; and the fact that this Killer requires tough Sudoku logic and so plays more like a 1-10 regular Sudoku than a 1-10 Killer… once you get going, that is!
Good luck!
Samurai Toroidal Killer Sudoku Pro 13-grid
May 7th
Samurai Toroidal 13-grid Killer Sudoku Pro puzzle
Now this is a puzzle I can state with confidence that you won’t have seen before. It’s a Killer Sudoku Pro puzzle – i.e. a Killer Sudoku with -, x and / regions too; but more than that it’s a Samurai Killer Sudoku Pro made out of 13 grids; and then further still the cages are toroidal, both around the edge of the grid and across the gaps. In other words, the Killer Sudoku Pro regions aren’t bounded by the actual physical layout of the 13-grids – they either jump the gap (in a straight line) or wrap around the edges of the puzzle (again in a straight line, albeit one that jumps to the other side!).
If you like huge puzzles then you should really enjoy this, assuming you can print it out large enough to actually have a chance of solving it! For everyone else, I’ll post some more smaller puzzles soon! It’s not actually very difficult, logically, but completing the whole thing would still take a fair while – perhaps a couple of hours, I think.
The rules are:
- Place 1-9 into each row, column and 3×3 bold-lined box of each of the 13 underlying 9×9 Sudoku grids
- Place numbers into each dashed-line cage so that all together they give the total at the top-left of the cage once the given operation is applied – for subtraction and division start with the largest number in the cage and then subtract/divide-by the other numbers.
- Numbers can not be repeated in a cage.
- Some cages continue across the gaps – just use an imaginary straight-line rule to follow them on and find the rest of the cage (so for example if a cage runs across a gap in the 3rd row down, it continues on the other side of the gap also on the 3rd row down)
- Some cages continue across the edges of the grid – these wrap around to the same row or column on the opposite side of the puzzle
If you try it: Good Luck!
Toroidal Killer Sudoku Pro
May 7th
Toroidal Killer Sudoku Pro puzzle
Here’s something that I’ve actually never seen before – Killer Sudoku with toroidal cages. Perhaps there’s a good reason for that, but it’s time to find out. This is actually a Killer Sudoku Pro, so it doesn’t just involve addition – but you cannot repeat a number in a cage, unlike in CalcuDoku.
So the rules are:
- Place 1 to 9 into each row, column and bold-lined 3×3 box
- Place numbers in each cage to add/multiply/subtract/divide up to the total at the top-left of each cage
- Numbers may not repeat in a cage
- Some cages wrap around the edges of the puzzles, continuing directly opposite
This is rated ‘gentle’, and none of the toroidal cages are very large so shouldn’t be too confusing to follow (I hope!).
Good luck!
Killer CalcuDoku +/-
May 2nd
Killer CalcuDoku +/- 6×6 puzzle
There’s a lot of very interesting puzzle space to explore between the extremes of Killer Sudoku and KenKen (a trademark of Nextoy LLC, so I will always refer to this as CalcuDoku from now on, unless anyone suggests a better name!).
I’m going to define two in-between puzzles, giving a continuum like this:
- Killer Sudoku
- Killer Sudoku Pro – Killer Sudoku with extra operations (+, -, x, /)
- Killer CalcuDoku – Killer Sudoku Pro with repeated digits in cages, like CalcuDoku
- CalcuDoku – Killer CalcuDoku puzzles without box constraints (e.g. no 3×3 boxes)
To avoid confusion I’m going to draw Killer Sudoku and CalcuDoku the way they always are – with dashed-line cages in the first case and bold lines between squares for the latter (replacing the traditional Sudoku bold lines). Then to distinguish the others, Killer Sudoku Pro will appear exactly like Killer Sudoku except that there will be additional operators within the grid (for operator-less ones I’ll include a question mark “?” or similar after each clue). Killer CalcuDoku, meanwhile, will appear exactly like today’s puzzle – with solid cages within the main puzzle.
Now just to spice things up further, I’m going to mess around with how the puzzles work. Remember that the key difference between Sudoku and Killer Sudoku is that the digits now actually have value as well – so by fiddling with those values we can create an infinite range of new puzzles that solve in quite different ways.
Example Killer CalcuDoku +/- solution
Today is a good example: here’s a 6×6 +/- Killer CalcuDoku. The aim is to place -3, -2, -1, 1, 2 and 3 into each row, column and 2×3 bold-lined box, and to place numbers so that the inner cages compute to the value given when applying the stated operation to the set of numbers in that cage. Subtraction and division are again defined as starting with the highest number in that cage (so remember that 2>-3!) and then applying all the other numbers in any order – so for example the solution to a “4-” cage could be “1 and -3″. Confused? See, I said it would mix things up! (1 – -3 = 4)
I’ve included an example (trivial) 4×4 Killer CalcuDoku +/- solution so you can be sure you understand how it works. But you might not need it – it’s actually a very gentle puzzle I’ve attached, as you’ll probably soon find out… (well, once you get your head around the negative numbers!)
Good luck!
Killer Sudoku Pro / All Signs
May 1st
Killer Sudoku All Signs puzzle
Here’s a Killer Sudoku with “all the signs”, or Killer Sudoku Pro if you prefer. If you’ve got any ideas for a better name let me know!
As in a regular Killer puzzle, you can’t repeat a digit within the solution to any cage. Unlike in a regular Killer, all non-single cages specify the operation that is applied to produce the result given. If the operation is + or x then just add or multiply all the digits to give that total. For subtraction and division you must start with the largest number in the region and subtract or divide the other numbers from that to give the stated result (this is what you’d do intuitively, I think, but since these operations aren’t commutative it’s necessary to state this!) Other than that, regular Sudoku rules apply: place 1 to 9 into each row, column and bold-lined 3×3 box.
The logic is once again simple, as a first example of this puzzle type, but I think the wider range of operations brings a freshness to the puzzle. Let me know if you agree (or disagree!).
Good luck!
Killer Sudoku Multiplication
Apr 30th
Killer Sudoku Multiplication 9×9 puzzle
Killer Sudoku Multiplication 6×6 puzzle
I thought it would be interesting to see what a Killer Sudoku puzzle would look like if every operation in it was multiplication, so I decided to try it out.
The puzzles attached aren’t labelled with ‘x’ signs, but it should be fairly obvious from the totals that addition is not enough! Single-cell regions are simply equal to the stated value, but in all others you must multiply all of the cell values together to give the total at the top-left. Note that this follows Killer Sudoku rules, so a number cannot be repeated within a region.
These are all definitely rated ‘gentle’ – the logic required is simple, even though the multiplication might appear intimidating! In actual fact you don’t need to calculate most of the big values – try the 6×6 puzzle first to see why this is.
Good luck!
PS Subtraction and division are less interesting, unless you allow negative or fractional numbers! I’ll probably post examples of both the next couple of days anyway however!
Samurai Star Killer Sudoku
Apr 29th
Samurai Star Killer (gentle) puzzle
“Star Killer” sounds like something out of science fiction, but it’s now definitely reality with this 5-grid Killer Sudoku puzzle. The actual Killer part uses the most basic logic imaginable, and there are a lot of ’singleton’ regions which I’ve never used in a Killer puzzle before. The reason for this is that I wanted to start at a gentle level – as a result this mostly solves like a regular Samurai Star (a.k.a. Flower Samurai) puzzle, with the Killer regions used occasionally to either get you going or help you out with a quick number along the way. It shouldn’t take you much over 20 or 30 minutes if you’ve solved this shape of Samurai before, and know what a Killer Sudoku is!
The rules are pretty simple: place 1 to 9 into each row, column and bold-lined 3×3 shape of each of the 5 underlying 9×9 grids (there’s one in the centre too), whilst also placing numbers so that the total in each dashed-line cage is equal to that given in the top-left corner. You may not repeat a number within a dashed-line cage.
The puzzle has rotation symmetry order 4, so the cages are in a pleasing pattern I hope – I particularly like the hole in the square in the centre! I think by and large that if you can create the cages or givens in a puzzle with the same order of symmetry that you have for the grid layout itself that this generally leads to a more pleasing appearance for the puzzle; but more than this, I find that this tends to follow through with the solving process, and you end up with pieces of the puzzle that feel ’sympathetic’ to one another, since the symmetry leads to related discoveries. However it’s perhaps not clear that this solving benefit carries through to a puzzle this large, and it’s probably the case that a puzzle with entirely random cages would feel just the same to actually solve at this size. But it wouldn’t look as nice!
Coming up in the following days I’m going to experiment in the space between Killer Sudoku and Ken Ken™ – in other words, using more operations than just addition, and possibly allowing repeated numbers in cages (although not on puzzles with 1-9 to place!). I already came across a puzzle called ‘Killer Sudoku Pro’ in the Saturday Telegraph newspaper (UK) – in this they keep the Killer Sudoku rules about not repeating digits in a cage, but specify different operations for cages (in actual fact the rules aren’t stated next to the puzzle in full, but I presume repeated digits are disallowed - it certainly solves okay with that assumption!). I haven’t seen anything precisely like that elsewhere and I thought it was actually quite fun (it wasn’t too hard!) so I’ll definitely try making some of those soon for sure. If you have any other ideas for how to mix these different types together feel free to post a comment!
Good luck!
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