Isolation diary: Cracking the Miracle Sudoku

This morning I discovered the Miracle Sudoku – so the chances of my getting anything else done today went out of the window.

I’m fairly obsessive about sudoku, my current favourites being the killer variety. I usually do one in the newspaper over lunch, plus another couple on an app in the evening before going to bed.

But the Miracle Sudoku is something else, as you can see from the image. It contains exactly two numbers, so is unsolvable as it stands, of course. The point is that three extra rules are introduced to the normal sudoku rules. These are:

  1. Anti-knight rule: No two squares that are a knight’s move apart may contain the same number.
  2. Anti-king rule: No two touching squares (vertically, horizontally or diagonally) may contain the same number.
  3. Non-consecutive rule: No two squares that are horizontally or vertically adjacent may have consecutive numbers.

If you want to have a go you can download a printable version of the Miracle Sudoku above, together with a couple of practice ones. Be warned – you will need to print several copies!

In the process I have come across Cracking the Cryptic – a YouTube channel devoted to solving the Times cryptic crossword and sudoku.  It is run by two experts: Mark Goodliffe and Simon Anthony, who have both represented the UK in the World Puzzle and World Sudoku Championships – no, I didn’t know either.

On 10th May Simon Anthony was presented with the Miracle Sudoku for the first time and solved it live in around 20 minutes. (Spoiler alert: demonstrates the solution!)

As I write, at around 12 midday, I have managed to fill in all the 1s, 2s and 3s, and I promise I haven’t watched the video yet. I really must get dressed and clean the bathroom. Updates to follow.

Later: I have finished my chores and returned to the puzzle – and solved it!!!

I have now watched Simon Anthony working on it, and was delighted by his initial reaction – he thought he was probably being trolled by his colleague; either that or it was a work of genius. It gradually dawned on him that it was the latter. “We are watching magic unfold here”, he says at one point. “The universe is singing to us.”

I had to do the puzzle on paper, working on several sheets so I could back track when necessary. It would be good to have an app where I could enter my own starting numbers.

The purist in me is not entirely happy about some of the strategies I used to solve the puzzle. At one point, when I was finishing the 1s and 2s I had to make a speculative choice between two alternatives, then make further choices, backtracking along the paths as I hit errors. This is standard brute force problem-solving technique, but I usually try to avoid it when doing puzzles. Simon Anthony got stuck at the same point, but he moved on to the 3s and discovered the domino ring effect (you’ll have to watch the video), which helped him to progress much more elegantly.

A week later Simon Anthony was presented with a new Miracle Sudoku  – and solved it.

 

 


Please note

We have been in full self-isolation since 16th March to protect my husband whose immune system is compromised.

If you are in self-isolation then join the Lib Dems in self-isolation Facebook group.

You can find my previous Isolation diaries here.

 

* Mary Reid is a contributing editor on Lib Dem Voice. She was a councillor in Kingston upon Thames where she is still very active with the local party.

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3 Comments

  • Caron Lindsay Caron Lindsay 23rd May '20 - 6:00pm

    Oh my goodness. That looks so hard.

    I love that you have probably got our entire Sudoku loving readership busy for the entire bank holiday weekend though

  • Charles R Cochems 23rd May '20 - 6:52pm

    As shown in the video, no guessing is required. There is indeed a pure solution. Simple elimination gets you pretty far, and only checking for immediate contradiction is required after that.

    The miracle is that the puzzle is an easy solution, despite the incredibly low umber of givens.

  • @Charles R Cochem – did you manage to solve it before watching the video?

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