Category Archives: Puzzles

Puzzle 149: Skyscrapers²

The WPC 2017 in Bengaluru is over. Here’s a puzzle from my very thin set of preparation puzzles. It’s from a round with original types that applied the same set of rules “twice over” in a sense.

Rules Solve the grid as a regular skyscrapers puzzle, digits 1 through 5. In addition, small clues in the outer corners are skyscraper clues for the regular skyscraper clues along the outside. These 20 regular syscrapers clues are part of the solution.

For example, the regular skyscraper clues along the left side could be something like 1,3,5,2,2 to satisfy the second-level 3 clue in the top left corner.

Or see the rules of Round 20: Puzzle Fusion in the WPC instruction booklet, available at the WPC page. You can find an example there, too.

You can check your solution and solve online here.

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Puzzle 147: Skyscrapers Domino Construction

Here’s a puzzle that I made as a Christmas present.

skyscraper-domino-construction-tree

Rules Place the given set of dominoes in the marked domino tiles. Whenever two dominoes touch by an edge, the adjacent numbers must be the same. Clues outside the grid are skyscraper clues: They indicate the number of visible skyscrapers when looking along the corresponding row or column from that point, where each number represents a skyscraper of that height. Skyscrapers are blocked from view by those of greater or equal height.

Puzzle set: Classic Sudokus, 2017 East Asia Sudoku Championship

Last Sunday, South Korea hosted the Asian Sudoku Championship in Seoul, which included a set of classic Sudokus that I wrote.

These originally came out of practicing my Sudoku construction skills by writing a puzzle a day for a long week early last year. It’s still a hit-or-miss process for me, but I think there were some nice ones. Solve on PZV (a b c d e f g h i) or find the set below.

In other news, don’t forget to take part in Puzzle Ramayan at LMI this weekend: A set of easyish classics and region puzzles that I prepared, including some instructionless variants.

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Puzzles 145, 146: Masyu

Towards the end of last year Grant Fikes ran a puzzle construction contest on his blog: instructions, results. With the aid of random.org, I managed to defend the title from the previous Logicsmith Exhibition, tied by score with Nikola Zivanovic.

The objective was to construct a 10×10 Masyu puzzle that leaves over a battle ship fleet of empty cells while minimizing the number of clues. That turned out to be quite a fun challenge, and led to some rather nice puzzles, which I didn’t quite expect. I was a bit worried the contest would be won by optimal computer-generated submissions, but it seems no one went to that effort. Instead, I’m left curious as to how close to the optimimum we got with 8+7 clues.

Here are my two submissions (rules).masyu-logicsmith-2(solve on pzv.jp)

masyu-logicsmith-4(solve on pzv.jp)

Puzzle 144: Easy as ABC (Zehnkampf)

Last weekend I took part in a puzzle decathlon, run by Berni of croco-puzzle. That involved 10 rounds modelled on the athletics decathlon, where the running events mapped to puzzle solving (the hurdles were possible broken puzzles), jumping events mapped to puzzle creation, and throwing events mapped to optimization puzzles. A lot of very original ideas, and overall it worked very well. Puzzles and results are available at logic-masters.de.

One of the construction rounds, the Pole Vault, gave you three tries at constructing a high-scoring Easy as ABC puzzle: Before each attempt, you chose a grid size, then had 15 minutes to extend a partially clued puzzle of that size to a correct puzzle. The score was calculated by subtracting twice the number of added outside clues, five times the number of inside clues and once the number of diagonal adjacencies in the solution from ten times the number of rows/columns. I had a rough start there, but ended up with a pretty good third try, with this 8 by 8 puzzle.

easy-zehnkampf

Rules Place letters A-C into the grid so that each letter occurs once in each row and column. Clues indicate the first letter in the corresponding row or column.

Puzzle set: 24 Hour Puzzle Marathon, 2016 edition

Took me a bit longer this year, but here’s my set for the 24 hours from April. I took a bit of a different approach this year, with four puzzles each of six more or less standard puzzle types. My hope was to make the round a bit more approachable than in previous years, though this may have been taking it a bit far. But I think the round worked out fine in the contest.

Individual puzzles below, or get the whole set in PDF: 2016-24h-rob-puzzles.

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