This Clueless Easter Monster may cause a brain Explosion!!!

[Børge]

A brain Explosion may be the result of trying to conquer this Clueless Easter Monster, a true "Hellish Nightmare"

Yet another Clueless Easter Monster?
Yes, another Big Brother of this Easter Monster. And this one laughs of its Special Clueless brother and its resilience, and says: "My hide is impenetrable. My first victim was JSudoku, which logic could not bring me down. But in a long and fierce battle, SudokuSolver slayed me with 765 strokes."

Boldest of knights, my all Sudoku guardian angels be with you throughout your battle.



000000000000000005000308017000004002000000500000067080070046000000000900086100003
000000000000000009000300108000000000000001900080004002002006000003000004098040065
000000000000000008000000017006001002000006000009003100050087000000000000080090203
000000000000000006000008047003004000005000000004090060057040032000002008000003601
000000000000000000000060457000002008002001000009300000050010070000007003070094060
000000000000000004000020530008000010004000900060057000001006005000000000096701300
000000000000000004000006100007001002001000000002800040040052003000000009003670000
000000000000000009000009516000000000000004000001803040003071002000000000060002001
000000000000000008000000105006009000000005006008000300001050090000004207090072060



Not the very boldest of knights? Then this impostor is likely more your style. It is easily conquered.



000000000000000305000308017000004002000000500005067080070046000000000901086100003
000000000000000009000309108000000000000001900080004002052006000003000004098040065
000000000000000008000020417006001002002006000009003100050087000000000000080090203
000000000000000006000008547003004000005000000004090060057040032001002008080003651
000000000000000006000060457000002008002001300009300000050010070000007003070094560
000000000000000004000020530008000010004000900060057003041006005000000000096701300
000000000000000004000006170007001002001000000002800040040052003000000009023670000
000000000000000309000009516000000000000004008001803240003071002000000000060092001
000000000000000008000000125006009000000005006008040300001050090000004207090072063


If anyone is interested, between these two extremeties there are 12 other versions of varying difficulty. Look here.

[Glyn]

Børge

After I mentioned it I realized that the intractability of the Easter Monster would only be apparent if the Clueless grid actually stalled for all logical techniques. (Not including Steve Kurzhal's breakthrough or Champagnes 'Full Tagging Method'). The Clueless variants given here are 'solvable'.

I can envisage a multi-grid puzzle where all grids stall individually but that is still solvable by logic. The only example I have seen so far is the Ronin Samurai that Ruud posted some time back. A logical solution requires intergrid AIC (Chains spanning two or more grids). No solvers yet have such a bizarre capability as far as I know. It is interesting to speculate whether intergrid Fish can also occur. These techniques might enable one supermove to reduce the complexity of other moves further on.

[Børge]

I can envisage a multi-grid puzzle where all grids stall individually but that is still solvable by logic.

As can I. But one thing is envisaging this, another thing is actually constructing it. The first step would probably be to write a (DLX based) brute force solver, ensuring that there is one solution only.
Then one can start the contruction and if every grid is unsolvable by all available logical solvers, you could be on the right track. The hard part is then actually solving such a 10 grid monster by logic.
Any Vulcans around?

Ever tried:

Qassim Hamza

000700800000040030000009001600500000010030040005001007500200600030080090007000002

OR

Top 1465 Number 77

700000400020070080003008009000500300060020090001007006000300900030040060009001005


More info the end of http://en.wikipedia.org/wiki/Algorithmics_of_sudoku

[Glyn]

Børge

By the way the Wiki entry is a little out of date, these are not considered to be at the forefront at the moment at least for Solver programs. The best place to get the latest info is

Hardest Sudokus

Finding a nest of them in a Clueless would be a nasty surprise. Perhaps the Vulcans would rather move on to 4-dimensional chess.

[Børge]

The ultimate challenge would probably be to construct a Clueless puzzle where ALL the 9 outer grids are solvable by using extreme logic only (not supported by any known computer based solvers), and only up to a point X. Solving further than point X should only be possible with pure guessing, but at this point and NOT EARLIER should it be possible to solve a couple of cells in the Clueless grid, again using extreme logic only. Then it should be possible to solve a couple of cells in one or several of the outer grids, then in the Clueless grid, and so on until the complete puzzle is solved.

When I evetually retire, I might find the time to take a closer look at constructing such a puzzle.