All 3 entries tagged Sudoku Islands

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August 13, 2010

Friday Puzzles #65

Welcome once more to another edition of Friday Puzzles! To those who are just (de)tuning in, I’d like to introduce you to my own pet sudoku variant, Sudoku Islands. The idea is the result of blending Sudoku and Nurikabe together. I’ve realised that since introducing them earlier on in the summer I’ve not really given a proper description of the rules. So here goes:

Place the digits 1-N in the grid such that each digit appears exactly once in each row, column and marked S×T box. The cells containing digits form a connected region of the grid, not containing any 2×2 block of cells. The remaining cells are shaded islands, whose sizes are given. Each island is clued in the grid.

Previously, N has equalled 5, and S and T have both been 3. Here’s a little recap in case you were wondering how that looks practically.

#079 Sudoku Islands – rated medium

This example ramps up N to 7, and S and T have become 4 and 3. 12×12 classic Sudoku puzzles are something of a drag; I’ve intentionally made this one fairly difficult, although I’m not quite sure whether this size again makes things a little bit fiddly. Let me know what you think!

#080 Sudoku Islands – rated hard

All puzzles © Tom Collyer 2009-10

July 02, 2010

Friday Puzzles #59

So a week or two back I saw a wonderful twist on the rules of heyawake, courtesy of Grant Fikes. I’m sure the more adventurous browsers of this blog will have already come across his wonderful page, but for those who haven’t then give it a visit.

Anyhow, the twist is this: instead of numbers in the rooms indicating which squares should be shaded in, rooms are labelled with either S, A, or not at all. Rooms labelled S should have squares shaded in with 180 degree rotational symmetry (which includes no shading at all), whereas rooms labelled A definitely cannot have that 180 degree rotational symmetry. Rooms with no label can be shaded any which way you like, provided you don’t break the other heyawake rules, which if you’ve forgotten can be found on the very handy “how to play” section there on the left. Anyhow, Grant’s puzzle was fairly gentle, but here I’ve been a bit keener to explore some of the logic, and how it interplays with some standard heyawake tricks.

#070 A/S Heyawake – rated hard

I should also mention that some puzzles from a while back have been featured in the 8th edition of Dr. Gareth Moore’s Sudoku Xtra magazine. This is quite a cool magazine, and whilst I should stress that I’m receiving no commission or anything, it is definitely worth a look for all you puzzle fans – it’s packed with a lot of nice puzzles. As well as those WSC5 style puzzles I did, it features the Sudoku Islands puzzle from last Friday. So what the heck…here are a couple more. These are definitely on the easy side of things, but I do have some trickier ones in reserve that are part of my ongoing sudoku project. Enjoy!

#071 Sudoku Islands – rated easy

#072 Sudoku Islands – rated easy

All puzzles © Tom Collyer 2009-10

June 25, 2010

Friday Puzzles #58

This week dear readers, I am appealing to you for a little feedback. It seems every puzzle designer worth their salt has their own pet sudoku variant they’ve created, nurtured and loved. Oh the long days I looked on in envy!

Anyhow, today that all changes as I’ve come up with something that is (a) original to the best of my knowledge and (b) isn’t totally lame. I call it Sudoku Islands. The idea is basically a hybrid of sudoku and nurikabe. You have an NxN grid, and the idea is to fill in each column, row and box with the digits 1-M, where M < N. Moreover these digits form a connected region of the grid, with no 2×2 blocks, which surround islands. The size of these islands is clued by the grey squares, and there is exactly one given clue per island in the solution. Unfortunately if you are used to nurikabe much, the roles of white and grey (black) squares have become reversed, but you’re playing by my rules now so I guess that’s hard cheese!

What you get is in my mind something that works out to be an improved version of extra space sudoku, where you not only have to fill in the grid, but also have to work out where the extra space is. That’s all beginning to sound a bit wordy, so here’s a really easy toy example for you to get the idea. Fill this grid with digits 1-4 in each row/column/box:

#068 Sudoku Islands – rated very easy


And this one with digits 1-5. Enjoy!

#069 Sudoku Islands – rated medium

All puzzles © Tom Collyer 2009-10


Welcome to the blog of current UKPA sudoku champion, two-time Times national sudoku champion and general logic puzzle fan Tom Collyer.

Home of the original Friday Puzzles, each Friday I publish a 100% original and handmade logic puzzle, inspired by the world-famous Nikoli company.

How to play:
AkariFillominoHashiHeyawakeHitoriKakuroLITSMasyuNumberlinkNurikabeRipple EffectShikakuSlitherlinkSudokuSuraromuYajilin.


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Latest comments

  • I like the appearance of the solution. :P Nice one. by Prasanna Seshadri on this entry
  • I think I've seen something vaguely similar in some of Palmer's puzzles as well. To be honest I've a… by on this entry
  • That's two puzzles in a row where I find something I had used before. I know, not plagiarism; just g… by Bram on this entry
  • Kota, that's not really true. I had made my puzzle before going to the WPC already. Also I don't hav… by Bram on this entry
  • About 20 minutes, after restarting from a mistaken conclusion. by Bryce Herdt on this entry

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