Friday Puzzles #302

Here's a puzzle I don't believe I've posted publicly yet, but I think might be interesting to solve.  X-Sums Sudoku has some clues outside the grid indicating the sum of the first "X" numbers placed in cells in the corresponding direction, such that "X" is the number placed in the closest cell. For example an outside 3 means the numbers placed would be 2 followed by 1.

Enjoy!

    #343 X-Sums Sudoku – rated hard

All puzzles © Tom Collyer 2009-19.

Friday Puzzles #294

This one is fairly tricky too.  Enjoy!

   #335 Diagonal Sudoku – rated hard

All puzzles © Tom Collyer 2009-17.

Friday Puzzles #293

Yes it's not Friday any more.  This should keep you busy for a while!

   #334 Irregular Sudoku – rated hard

All puzzles © Tom Collyer 2009-17.

Friday Puzzles #292

Can you tell what it is yet?  Small packages can still sometimes pack a punch!

1 to 7 once in each row and column, and at most once in each 6 cell region.  Enjoy!

    #333 Deficit Sudoku – rated hard

(A fixed version of a previous puzzle)

All puzzles © Tom Collyer 2009-17.

Friday Puzzles #285

In celebration of George Boole's 200th birthday, and Bram de Laat's excellent Clone Or Extra Region Sudoku, I give you Clone And Extra Region Sudoku.  Enjoy!

Rules: the two shaded regions contain each of the numbers 1-9 exactly once.  Moreover, the same numbers go in cells with the same relative position in the two regions.

    #325 Extra Region And Clone Sudoku – rated hard

All puzzles © Tom Collyer 2009-15.

Friday Puzzles #283

Well I've been and gone to the world championships in Sofia, Bulgaria.  Expect some kind of write up in the next week-ish, although I'm not sure I have the heart or energy to go into the kind of detail I normally do.

Abbreviated results are:

WSC: 49th -- GBR-A: 8th
WPC: 45th -- GBR-A: 7th

I'm pretty happy with both sets of team results, just about happy with the WPC result and pretty disappointed with the WSC result.

Congratulations to our two new Japanese world champions Kota Morinishi (WSC) and Ken Endo (WPC).  Japan and Germany won the respective team competitions.

A new fixture during world championship week are the two WPF Sudoku and Puzzle GP finals.  I still have a few thoughts about these competitions which I will save for another post, but as a UK author for the 8th leg of the Sudoku I also had the honour of contributing two puzzles for this play-off.

One of them was a classic, which got selected.  Nothing hugely special, but it was probably at a medium difficulty level as opposed to my normal easy level.  I was a little disappointed that my variant didn't get picked, which was a hybrid Renban-Killer variant.  So instead I get to share it here with all my dearest readers!

Rules: numbers placed in cages don't repeat and sum to the given clue.  Numbers placed in shaded regions don't repeat and form a consecutive set.

Enjoy!

    #323 Renban-Killer Sudoku – rated hard

All puzzles © Tom Collyer 2009-15.

Friday Puzzles #272

I'm not quite sure I'm in a state to judge the difficulty of this puzzle any more. Enjoy!

    #311 Non-Consecutive Sudoku – rated hard

All puzzles © Tom Collyer 2009-15.

Friday Puzzles #271

Whilst I've been travelling far and wide across Eastern Europe this week, I've still managed to find the time to make a puzzle.  The initial idea for this was a lot cleaner but it didn't quite turn out to solve uniquely.  So I've fiddled with some of the clues a bit and now it is unique, but a little harder than intended.  Or at least that seemed to be the case to me whilst going through it on the train.

In case you needed reminding, consecutive pairs is much like consecutive, only not all the pairs are given.  Much cleaner in my opinion, and much nicer to look at.

Enjoy!

    #310 Consecutive Pairs Sudoku – rated hard

All puzzles © Tom Collyer 2009-15.

Friday Puzzles #261

Hurray!  It's another Christmas Tree Sudoku!

• Givens take the shape of silly decorations.  There is nothing else to say about these.
• The tree (anything shaded green or brown) acts as a fortress.  Which is to say numbers placed in the fortress must be strictly greater than those placed in the immediately adjacent  cells outside the fortress;
• Silver circles (fairy lights?!  Tinsel!?!) marking some pairs of adjacent cells are as in Parity Sudoku.  Which is to say one of the numbers to be placed must be odd and the other must be even.  Not all such pairs are marked
• White circles (erm, stars!?) marking some pairs of adjacent cells mean the corresponding two numbers to be placed must be consecutive.  Not all such pairs are marked.

Nice and easy.  Enjoy!

   #300 Christmas Tree Sudoku – rated hard

All puzzles © Tom Collyer 2009-14.

Friday Puzzles #241

A happy new year to all my dearest readers.  Given that both 20 and 14 are even numbers, and 405 is not, there's a fairly obvious diminishing returns thing going on with the tweaking of the uncaged cells.  C'est la vie.  Enjoy!

    #278 Killer Sudoku – rated hard

All puzzles © Tom Collyer 2009-14.

Friday Puzzles #238

In case you didn't see, I posted an easy masyu for last week's puzzle.  This week, something much harder.  As always with this variant, numbers placed in cells related by a chess knight's move must be different.  Enjoy!

    275 Anti-Knight Sudoku – rated hard
 

All puzzles © Tom Collyer 2009-13.

Friday Puzzles #224

I think, Dearest Reader, you'll learn something new when solving this puzzle.  Enjoy!

    #261 Irregular Sudoku – rated hard

All puzzles © Tom Collyer 2009-13.

Friday Puzzles #217

Seems I was very naughty on Friday and forgot to make a blog post.  Rest assured dearest reader, it did appear on the facebook group in good time so if you've been following the daily league and haven't yet joined up, then why not?

Week 26
Saturday (Gapped Non Consecutive, Gui Yong)
Sunday (Anti-Knight, Seungjae)
PDF

Week 27
Monday (Triangle Sums, Zoltán Horváth)
Tuesday (Frame, Prasanna)
Wednesday (Non Consecutive Anti-Knight, Bastien) - this is a very powerful combination of constraints!
Thursday (Renban Groups, Jan Zvěřina)

As always, you can play with a day's delay on the sudokucup.com servers.

This week's puzzle is a difficult diagonal sudoku.  Probably too hard for competition.  Enjoy!

    #254 Diagonal Sudoku – rated hard

All puzzles © Tom Collyer 2009-13.

Friday Puzzles #214

More daily league sudoku - but perhaps you might be able to see some other puzzle types from me elsewhere sometime soon.  More on this to come, hopefully.

Don't forget you can play online with a day's delay at sudokucup.com!

This week is a continuation of last week's idea.  I think this is a variant with lots and lots of potential.  This isn't a particular beautiful puzzle to look at, or to solve, but at least it should provide something of a challenge.  This certainly took a while to test solve last night! 

Oh and the rules: consecutive terms of the sequence to be place on the marked line should differ by at most 2.  Which means they can differ by 0, 1 or 2.  Enjoy!

    #251 Chinese Whispers Sudoku – rated hard

All puzzles © Tom Collyer 2009-13.

Friday Puzzles #209

After UKSC duty, I'm back to the daily league.  I'm going to sit down and do a bit of an update of all PDF related stuff tomorrow.  In case you were wondering, we are up to Week 19 now - and scattered through the facebook group are links to the PDF's up to week 17.  Week 18 will come tomorrow as well, honest!

So I was up til about 4am tweaking this puzzle until it was just right.  In case you were wondering whether I can do hard puzzles, here's an extra regions puzzle which will push your geometric understanding of the added constraints quite far.  Let me warn you now, until you work out exactly what is going on, you aren't going to make much progress.  Puzzles like these where there are no freebies at the start, and where every given plays its own crucial role both by itself and in ensemble are very hard to come by, and I think this is probably as good a puzzle as anything I saved for the UKSC.  If not better!  And whilst I'm here blabbering on, I'm also going to take this opportunity to also point you towards Bastien's wonderful 16 given Diagonal. 

Enjoy!

    #246 Extra Regions Sudoku – rated hard

All puzzles © Tom Collyer 2009-13.

Friday Puzzles #202

I'm very very tired.  Tens sudoku.  Adjacent cells containing numbers summing to ten are both shaded. Adjacent cells which are not both shaded must not contain numbers summing to ten.  This is pretty hard.  Enjoy!

    #239 Tens Sudoku – rated hard

All puzzles © Tom Collyer 2009-13.

Friday Puzzles #193

When I am feeling less disorientated and delirious, I will post plenty of daily league updates, the Week 2 PDF, and a brief apology for this puzzle being hard and cool, but not nearly as hard or cool as it should have been.

For now, I'm already 10 minutes past Friday is up, although this won't trouble my dearest American readers.  If you've not already joined the facebook group, you'd have seen this puzzle a few hours ago anyway.  Enjoy!

    #230 Irregular Sudoku – rated hard

All puzzles © Tom Collyer 2009-13.

Bonus Christmas Puzzle

The multi-talented Tiit Vunk shared a Christmas themed Sudoku puzzle on facebook the other day and it inspired me to try something in a similar vein.  So here goes!

The Christmas tree itself acts like a fortress.  That is, cells that are part of the Christmas tree must contain digits which are strictly large than digits in adjacent cells which are not part of the tree.  There is no restriction for two adjacent cells which are part of the tree.  Where there is potential ambiguity as to whether a cell is part of the tree, I've filled it with a pale yellow glow.

Each piece of tinsel on the tree indicates an ascending sequence of digits in the cells that it covers.  it's up to you to determine in which direction.  Hopefully it's clear where the tinsel is going.  Please note that some pieces of tinsel are going diagonally between cells.

Finally the tree is decorated with some baubles and a star.  These have no significance other than to provide givens for the puzzle.  Upon test solving in paint, I found these decorations to be somewhat distracting.  I should also add that I haven't tried printing this, so hopefully I've chosen a shade of green that doesn't come out too dark.  Then again you'll have to live with this.  It's a Christmas tree, see.

Oh, and this one isn't for the faint hearted in terms of its difficulty.  But not so hard that you'll need to guess.  But hey, you've all got tons of free time on your hands, right?  Merry Christmas, Dearest Reader, and as always, Enjoy!

    #225 Christmas Tree Sudoku – rated hard

All puzzles © Tom Collyer 2009-12.

Friday Puzzles #187

Yes, I do have other things on my mind.  No, you don't need to guess.

Wish me luck, Dearest reader; and as always, enjoy!

    #223 Masyu – rated hard

All puzzles © Tom Collyer 2009-12.

Friday Puzzles #179

So I've not really been able to pick a stand-out puzzle from the WPC like I could from the WSC.  I think what I'm going to do is release my favourite puzzle from various rounds and then maybe do a vote or something for your favourite in a few weeks time.  What I can tell you now is that I'm not going to do a dominoes puzzle, and unfortunately the puzzle I have in mind from round 2 has uniqueness issues, so you might have to wait until tomorrow until this gets published.  Hey - at least I got this disclaimer out on Friday.  Ugh.  Sorry!

UPDATE: I suppose I should add fair warning.  I tested this puzzle after 5 pints of Guinness last night, and I was very pleased with the logic that I thought made this solve uniquely.  I'm not so confident that this has a unique solution now, but I have no time to re solve it at this moment in time as apparently I'm wanted on television.  Given the issues I had with uniqueness making the bloody thing I'll not be surprised if someone finds a second solution here...

Rules: (as taken from the WPC instructions)
Place some tiles (of size 1x2 squares) in the grid, with numbers 1 and 2 each.  Tiles can be rotated but they cannot touch each other, not even diagonally.  Numbers outside the grid indicate the sum of all the numbers in the corresponding row/column.

Enjoy!

    #214 2-1 Tiles – rated hard

All puzzles © Tom Collyer 2009-12.