A short “2016 UK Puzzle Championship” season begins with a piece about how to get started with the puzzles in the competition. The piece needs context, however; participants have frequently commented that there weren’t many easy puzzles in the contest, yet participants’ scores tended to skew relatively high, compared to previous years’ contests. It’s also worth pointing out that I tend to come near the bottom of the rankings table, typically beating about 20% or so of the other competitors. Accordingly, take what I say with a considerable pinch of salt – but, on the other hand, there aren’t many people talking about the puzzles. Considerable credit goes to James McGowan for posting links to practice puzzles in advance.
You are strongly recommended to download the puzzles, open them using the password 20_S3n3c_16 and look at them in parallel with this commentary. First and foremost, thanks to the puzzle authors for their contributions and to Liane, Alan and David for putting the contest together and making sure that it happened at all. I thoroughly enjoyed the event.
1. Bank Note Theoretically puzzle 1 is something that can be done quickly while you wait for all the rest of the puzzles to print out. I found this year’s tough for a puzzle 1, taking completely the wrong approach at the start. Treat the horizontal and vertical numbers separately, and write each row or column number as the sum of numbers from 1 to 5, such that each number appears once in one direction and in three adjacent rows or columns in the other direction. So the 1 means there can’t be anything in that row but a 1, so if there are vertical numbers then they must span the top three rows, which gives you a clue as to where the 5, 3 and 2 are.
2-3. Last Digit I solved puzzle 2 and entered it with less than ten seconds to go, which definitely beats finishing a puzzle just too late. Count up which gaps have 2 numbers pointing to them and which have 3 pointing to them. You can’t have a sum of three numbers from 1 to 7 being over 20, so the sum must be between 11 and 17. These puzzles were not popular with UK solvers.
4. Skeleton Crossword Word puzzles used to be easy but laborious, but these days they’ve got rather harder. I don’t see the breaking-in point here.
5-6. Paint it Black Railway You can extend the line in each direction one square from each of the crossover points, and thus determine the directions in which the line passes through stations 1, 4 and 6. The presence of a line in the square above the upper crossover point means that there are only three possibilities for row 5, and the fact that each column has only one black square cuts down on the possibilities for row 4. On the other hand, I used similar logic on puzzle 6 and kept running into contradictions, or at least chunks of the map where the line has to enter and exit through the same square, which is clearly wrong.
7-8. Magnets After muffing my first attempt at Bank Note, I tried puzzle 7 as my second attempt and ran into a contradiction fairly quickly here too. The starting-points are rows with particularly many or particularly few magnetic tiles; fill these in as either magnetic or non-magnetic first until you become clear what the polarity must be. You can practice the genre in the Simon Tatham puzzle pack, though solving it on paper differs more from solving it digitally than you’d think. I got puzzle 7 correct on my second attempt and didn’t touch puzzle 8.
9-10. Arrows I don’t see the breaking-in point and this genre did not prove popular with UK solvers. Plenty of examples are available for practice.
11. Star Battle An unusually large example of the genre that did not prove popular with UK solvers. It’s easy to identify lots of spaces where stars cannot be, but I couldn’t get far enough to actually place many stars. Plenty of examples are available for practice.
12. Battle Stars The starting-point would seem to be rows and columns with few possibilities, but I couldn’t break in to this one. Some examples have been published.
13-14. Clouds The zero column offers a start, and it’s easier to think in terms of rows and columns featuring 8 filled squares being all filled except for two squares which separate clouds through the “don’t touch each other, even diagonally” rule – and the “must be at least two in each dimension” rule cuts down the possibilities, so an 8 must be a 4-2-2 or a 3-3-2 in some order. Plenty of examples are available for practice.
15. Tapa Another fairly well-known puzzle style, but not one at which I am much good; I spent a few minutes and couldn’t get far at all. Plenty of examples are available for practice.
16. Dissected Tapa Tapa has spawned plenty of variants, probably not very many fewer than there are sudoku variants. I am told examples of these cropped up in this contest and contest 18 in the same series. I didn’t touch this.
17-18. Sum Skyscrapers Start by working out where the 5s must be. A 9 column could arise from a 4-5 or a 1-3-5, a 12 could be a 3-4-5 or a 1-2-4-5… and what the consequences would be when looking at the column from the “other end”, when you have values for both ends of a column. This is a variant of a well-known puzzle type in the Simon Tatham puzzle pack.
19. Hidoku This was the first puzzle I properly solved, after muffing a few attempts. Start in the lower left corner and work out which numbers you have no alternative but to place. This will all but fill in the lower left square, with a few strings of gaps. There are 104 squares to fill, so you can fill some of the gaps with 102 to 104 (for where else can they go?) and then 1 to 5. By this point you can work out what the numbers are in the squares between the big squares and then just treat it sas four smaller examples. Plenty of examples are available for practice and I think they’re in newspapers as well. The most frequently correctly solved puzzle on the paper.
20. Kakuro A large example but no particularly nasty tricks, though I think the bottom appeared to have two possible solutions, one of which could be ruled out fairly quickly because it broke the bottom right. The way to break into this is to break it into more manageable chunks and draw what conclusions you can, especially from sequences of particularly high or particularly low numbers – a 17 over two digits must be a 9 and an 8 in some order, a 16 over two digits must be a 9 and a 7 in some order, and so on. Again, plenty of examples are available for practice and I think they’re in newspapers as well.
21. Sum Snake A variant of the Snake format. An example was featured in another contest. I didn’t touch this.
22. Pearl Areas No clue.
23. Filled Pentominos Didn’t touch this either.
24. Sumpix I did solve this and was delighted to do so. The technique is to look at sums of adjacent numbers. As the lowest sum of four adjacent numbers is 1+2+3+4=10, the lowest sums of three adjacent numbers are 1+2+3=6 and 2+3+4=9, the sums of two adjacent numbers are either 3+4=7 or 4+5=9, you can conclude that the 8 column is an 8 only. From there, next look at the columns with totals near 55; the 50 column is missing 5 and thus could be missing 1+4 (i.e. 2+3+5+…+10), 2+3 (i.e., 1+4+…+10) or 5 (i.e., 1+…+4+6+…+10), and similar logic for the 51 and 52 columns, which means that you can mark in at least the 6s-to-10s in those columns. Next, look at the 39 and 40 rows, bearing in mind the 8 column. That’ll get you started.
25. Killer Sudoku Standard, though a 40-point example looked like it had the potential to be quite mean. You don’t need me to provide a link here.
26. Hashi Standard but large and very easy to make a mistake on at this size. You can practice the genre in the Simon Tatham puzzle pack, though solving it on paper differs more from solving it digitally than you’d think.
27. Suguru Another popular example of a style that I’ve never really got into as it’s so possible for a single mistake to ripple through and affect lots of other cells before you spot the error. Plenty of examples are available for practice.
28. Slitherlink Slight variant of a familiar style. You can practice the genre in the Simon Tatham puzzle pack.
29. Sum Fillomino Variant of a familiar style. You can practice the genre in the Simon Tatham puzzle pack (“Filling”) though I don’t know how to use the constraints of the variant to break in here.