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Escargot

In late November 2006, a Finnish applied mathematician, Arto Inkala, claimed to have created the world's hardest Sudoku.

"I called the puzzle AI Escargot, because it looks like a snail. Solving it is like an intellectual culinary pleasure. AI are my initials," he said.

"Escargot demands those tackling it to consider eight casual relationships simultaneously, while the most complicated variants attempted by the public require people to think of only one or two combinations at any one time", Inkala said.

This puzzle is available in the drop down list of examples in the Sudoku Solver. The solver cannot currently solve it, however, using the logical strategies at it's desposal. The brute force "Solution Count" can find the solution but such a method is less interesting than a logical solve route.

Escargot recieved a good deal of publicity in newspapers around the world.

Load Escargot

Go back to Cage SplittingContinue to Arto Inkala


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Comments Talk

Saturday 29-Oct-2022

... by: Dr, Chris

It is possible to solve this puzzle using only pencil and paper through logical analysis and a process of elimination. The top three blocks contain nine numbers, almost the numbers 1-9, but not quite: One number occurs twice, the 9 in A8 and C3. That means that either B4 or B6 must also be a 9, and because of the way the other numbers are arranged in these three blocks, the other of those two cells must be a 1, 4, or 5. In trying out those possibilities, it is not necessary to decide initially whether the 9 goes in B4 or B6 (although pairing the 9 with the 4 requires the 9 to be in B6); knowing the two numbers occupy those two squares is enough to place the rest of the numbers in row B in unique or almost unique locations. This is because A1=1; F1=6; D3=5 and I3=7; and C7=5. While it makes sense to try B4+B6=4,9 first because that places all of the numbers in row B, unfortunately that leads to a falsity. But B4+B6=1,9 leads to a solution, after a bit of experimentation to see where the 6 and 7 fit in B7 and B8.

Tuesday 16-Nov-2021

... by: S3ven_Six

This is definitively either not the real Escargot, or I found a much harder one.
I was able to spot a hidden 2468 quadruple in column 7, forcing a 17 pair that straight up solved the board. There are several other spots that if u just find 1 single digit, the entire board solves itself.

This is a more difficult puzzle that didn't take me 10 minutes to solve, but 2 hours of multicoloring, and contradiction testing, etc. -- with 2 times of straight up bifurcation.
https://f-puzzles.com/?id=yhtyjrzr

Friday 1-Aug-2014

... by: JPF Naperville, IL

The Escargot puzzle at aisudoku.com does not have a 1 at H3. Your solver added that via finned swordfish? Please clarify.
Andrew Stuart writes:

Weird. I've removed the one. It is a simple single.

Saturday 2-Jun-2012

... by: Leren

Escargot is harder than Andrew's Weekly unsolvables (except for no 49) but only requires first order forcing chain logic to solve, so it's not in the hardest class of puzzle. The 2010 puzzle by the same creator was similar but slightly easier.

Tuesday 22-Sep-2009

... by: lihsiaotung

"Escargot demands those tackling it to consider eight casual relationships simultaneously, while the most complicated variants attempted by the public require people to think of only one or two combinations at any one time", Inkala said

but I solved Escargot through considering seven casual relationships simultaneously with my solver. Maybe Escargot was not the most difficult Sudoku puzzle,I think.
Article created on 27-May-2008. Views: 69350
This page was last modified on 12-June-2008.
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