September 20, 2024

Can you solve it? Sudoku as spectator sport is unlikely lockdown hit

Spectator #Spectator

It may not be as hair-raising as Formula 1, nor as dramatic as Premier League football, but Sudoku solving is acquiring a niche following as a spectator sport.

It’s surprisingly thrilling, believe me. Just ask fans of the puzzle-solving YouTube channel Cracking the Cryptic, which has seen its viewing figures shoot up over the last two months. Its top Sudoku video has had more than 3 million views.

In daily challenges, the channel’s two British hosts, puzzle wizards Simon Anthony and Mark Goodliffe, narrate their strategies and processes of deduction as they attempt to solve fiendishly difficult Sudokus.

What makes the videos so joyous is the constant stream of ‘aha!’ moments, as well as the ingenuity of the sudokus presented. The puzzle I am setting today, the Miracle, appeared on the channel last week. (Click here for a printable page for all today’s puzzles. To solve them online there is a link underneath each grid.)

Miracle sudoku by Mitchell Lee. To solve online go here, to solve with pencil and paper print out this page

The Miracle is – hold your breath – an anti-knight, anti-king, non-consecutive sudoku, which means that as well as normal Sudoku rules (that is, the numbers from 1 to 9 must appear only once in each row, column, and cage) the following rules also apply:

1. Anti-knight rules: no two squares that are a knight’s move apart can have the same digit. (The knight’s move is 2 along and 1 to the side, as in chess.)

2. Anti-king rules: no two squares that touch either horizontally, vertically or diagonally can have the same digit. (As in, no two squares a chess king can move between in a single move.)

3. Non-consecutive rules: no two squares that are horizontally or vertically adjacent can have consecutive numbers.

Each of these extra rules brings a new dimension to Sudoku and the result is an exquisite puzzle, which dazzles by starting with so little information – just two clues! -and yet has a unique solution. Hence it’s name, the Miracle

As preparation for tackling the Miracle, here are two easier Sudokus, one with the anti-knight rule, and one with the non-consecutive rule. (You can print them both out here.) I’ve helped you with the first steps in each.

Anti-knight sudoku

Puzzle by Cracking the Cryptic. To solve this puzzle online go here, to solve it with pencil and paper print out this page

Normal sudoku rules apply, as well as the ‘anti-knight’ rule, in which no two squares that are a knight’s move apart can have the same digit. In other words, none of the blue cells in the grid below can contain a 4, because they are all a knight’s move from a 4.

Let’s start with the 4s. I have coloured in blue all the cells that are prohibited from having a 4, either because there is already a 4 in the row/column, or because of the knight’s move. The only available cells for a 4 in two of the cages are marked.

Non-consecutive Sudoku

Puzzle by Cracking the Cryptic. To solve this puzzle online go here, to solve it with pencil and paper print out this page

Normal sudoku rules apply, as well as the non-consecutive rule that no two squares that are horizontally or vertically adjacent can have consecutive numbers. (Meaning that a square that has, say, a 3, cannot be vertically or horizontally adjacent to a square that has a 2 or a 4.)

Again, I’ll start you off. Look at the blue square on the second row. It cannot contain a 1,3 or a 6 because these numbers are already in its row/column. Since it is adjacent to a 1, it cannot contain a 2, and since it is adjacent to a 6, it cannot be a 5. So it must be a 4. The green cell is a 1 because three of the other available cells in that cage are adjacent to the 2 (and thus cannot be a 1), and the last available cell is in a column with a 1.

Right! Solve these two simpler sudokus and then tackle the Miracle, which uses both the anti-knight and the non-consecutive rule. (And the anti-king rule, which is self-explanatory, and should be easy to get your head around now you have mastered the other two rules.)

If you struggle, you can always watch Simon at Cracking the Cryptic solve it in real time.

I’ll be back with the solutions at 5pm.

UPDATE: Solutions are now up here.

I set a puzzle here every two weeks on a Monday. I’m always on the look-out for great puzzles. If you would like to suggest one, email me.

If you are reading this in the Guardian app, and you want a notification each time I post a puzzle, or its solution, click the ‘Follow Alex Bellos’ button above.

Alex’s Adventures in Numberland Photograph: Bloomsbury

I’m the author of several books of popular maths. My first maths book, Alex’s Adventures in Numberland, has just been reissued to celebrate its tenth anniversary. The new edition is fully updated, including one section about the maths of Sudoku.

Thanks to Cracking the Cryptic and Mitchell Lee.

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