Wednesday, June 3, 2020

Miracle Sudoku

This video shows a guy named Simon Anthony solving a Sudoku puzzle with only two digits given. He and his partner have a very popular YouTube channel called Cracking the Cryptic. Anthony proceeds to solve the puzzle in about 20 minutes. His feat is impressive, especially with the extra rules he was given. In a common Sudoku puzzle, a solution cannot be unique with so few digits given. I have read that at least 17 or 18 digits are needed for that.  

Anthony’s full solution was as follows with the two given numbers in green.

483726159
726159483
159483726
837261594
261594837
594837261
372615948
615948372
948372615

His solution has recurring trios in the rows of every band and columns of every stack. For example, he entered 4 8 3 in rows 1-3 and 6 9 3 in columns 4-6. The order of digits within some trios aren't all the same. For example, there are 1 4 7 and 7 1 4 and 4 7 1.

I believed I might solve it faster using the copy and paste method I described in my May 27 post, with maybe a little tweaking after filling the grid.

The first digits I entered were as follows. I did the trio 2 6 1 first, then 4 8 5 and 7 3 9. 




























4 8 5 2 6 1


2 6 1





7 3 9


2 6 1



























Then I filled the rest of the grid as follows, which shows many recurring identical trios.


8 5 4 6 1 2 3 9 7
6 1 2 3 9 7 8 5 4
3 9 7 8 5 4 6 1 2
4 8 5 2 6 1 7 3 9
2 6 1 7 3 9 4 8 5
7 3 9 4 8 5 2 6 1
5 4 8 1 2 6 9 7 3
1 2 6 9 7 3 5 4 8
9 7 3 5 4 8 1 2 6

I finished this full grid in only 3 minutes, 36 seconds. It satisfies the king's move and knight's move rules. However, it violates the other extra rule. Pairs of successive digits appear next to one another, e.g. 1 2 and 4 5. I tried tweaking to get rid of them, but gave up after 20 minutes. 

Mr. Anthony's solution might be unique. Swapping rows 1&2 or rows 8&9 violate the knight's move rule. Hats off to him. 

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