2021 WPF Sudoku and Puzzle GPs

[detuned]

Lets experiment with a combined thread this year

https://gp.worldpuzzle.org

The schedules have been published for 2021. In general there is one competition every fortnight, alternating Sudoku and Puzzles. [Note the slight break in that schedule for June however!] The first of the 2021 competitions happens in two weekend's time:

Sudoku GP 2021
1st round - 15.1. - 18.1.- Bulgaria
2nd round - 12.2. - 15.2. - Serbia
3rd round - 12.3. - 15.3. - Turkey
4th round - 9.4. - 12.4. - France & Hungary
5th round - 7.5. - 10.5. - The Netherlands
6th round - 4.6. - 7.6. - India
7th round - 2.7. - 5.7. - Poland
8th round - 30.7. - 2.8. - Germany

Puzzle GP 2021
1st round - 29.1. - 1.2. - Poland
2nd round - 26.2. - 1.3. - Hungary
3rd round - 26.3. - 29.3. - Germany & Bulgaria
4th round - 23.4. - 26.4. - Switzerland
5th round - 21.5. - 24.5. - Japan
6th round - 11.6. - 14.6. - USA
7th round - 16.7. - 19.7. - Slovakia
8th round - 13.8. - 16.8. - France

[Feadoor]

Sudoku Round 1 starts tomorrow, and the instruction booklet is available here: https://gp.worldpuzzle.org/content/instruction-booklet

[pinkagape]

Any hints on Full Rank? Will there be four numbers starting in 1, four with 2 and so on?

[Feadoor]

Yes - that's essentially all there is to it. Any clue in the range 1-4 must start with a 1, in the range 5-8 a 2 and so on. The rest is standard Sudoku and comparing the values within each range of four to get further restrictions. It can be a lot to keep track of so I strongly suggest crossing a clue out once you are certain from your notation that however you complete the grid from that point it will be positioned correctly relative to its immediate neighbours.

[detuned]

Yes sadly full rank is one of the tedious types where you need to know "the trick". They all solve in roughly the same way:

Ranks 1-4: digit closest to the edge is a 1
Ranks 5-8: digit closest to the edge is a 2
...
All the way down to Ranks 33-36, where the digit closest to the edge is a 9.

Then you start faffing around with the 2nd closest digit to the edge and so on.

Unfortunately there isn't really that much solving variety with this variation.

[detuned]

Some other solving tips:

Diagonal consecutive: when using the negative constraint, bear in mind that if you have a 5 in a cell, then yes that rules out 4,6 in cells touching at a corner, but it can still be a 5. I often do that by mistake as the equivalent heuristic for consecutive sudoku would rules out the 5 (via the row/column constraint)

Diagonal 10s: similarly don’t forget that 5,5 is possible!

[Feadoor]

Preliminary results are out, the UK top 3 are:

32. Sam Cappleman-Lynes - 495
41. Jeremy Kong - 468
58. Tom Collyer - 412

The overall top 3 (Kota, Tantan and Tiit) are well clear of the rest of the field.

Puzzles-wise, I did not regret my decision to just keep guessing at the endpoints of the lines in the Extended Extra Regions until I found a configuration that solved. Perhaps I should have done that earlier though, before I spent nearly 10 minutes with only one digit in the grid.

[detuned]

I didn’t have a go at extended extra regions during time, and was pleased that I didn’t. It reminded me of why I lost interest in the GP last year. There seems to be a growing trend of puzzles that I find hard because they are fiddly and there is no sense of flow to my solve - actually I'm finding they aren’t that much fun or satisfying to solve. Have other people noticed the same?

No individual deduction was difficult for the extended extra regions, but it was a narrow solve path with lots of the deductions placed randomly. To have a puzzle like that take up nearly 20% of the test’s points doesn’t seem like a great way to keep people interested! I doubt you were the only person Sam to have solved via case bashing.

I lost 40 points to a silly mistake and a further 20 to being inadvertently timed out (by about 6 seconds :/). Although I’m solving more for fun than for score, I’m happy to see I’m still vaguely competitive on the leaderboard.

[Puzzle_Maestro]

The instructions booklet for round 1 of the puzzle GP is our at https://gp.worldpuzzle.org/sites/defaul ... nd1_IB.pdf

Looks to be a fairly unorthodox round, with a high concentration of maths/arithmetic based puzzles, around 75%. Of these the anti-knight products is clearly the worry; products is already hard enough as two (almost) uniquely solvable, disjoint puzzles, and if there’s a lot of ambiguity in resolving what goes in each row/column it could be very challenging. Suspect I’ll need to make a practice puzzle for this.

Prime paths doesn’t feel like it could plausibly have such high point values (all 21 2-digit primes is only 42 cells and should permit bifurcation on 2,4,5,6,8) but we’ll see...

[detuned]

Isn't products more a case of needing to be methodical and meticulous? I can see the solving path being fairly narrow (but hopefully not quite as random as per the sudoku GP above!) - and maybe a bit more fiddly when combined with the anti-knight constraint. I expect it's going to be quite a large size, but the same old tricks (consider the larger primes first) are likely to apply. I suspect once you've got a few of those down then thats where the anti-knight will start to come in.

It's worth noting that for mere mortals taking the test, if you ignore that particular puzzle there is still over 600 points worth of puzzles to have a go at. I suppose it depends on how well you back yourself vs the testers. It may well fall quickly to a well-chosen bifurcation...