Extreme Puzzle No.6

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Extreme Puzzle No.6

Code: Select all
`.4.1..9....5..8.1.....2.8.5.1.8..3.............3..6.9.2.6.5.....9.6..2....1..9.7.`

Merry new year to all.
yzfwsf

Posts: 307
Joined: 16 April 2019

Re: Extreme Puzzle No.6

Or thisone which is essentially the same:
Code: Select all
`.4.1..9....2..8.1.....3.8.2.1.8..5.............5..6.9.3.6.2.....9.6..3....1..9.7.`
urhegyi

Posts: 220
Joined: 13 April 2020

Re: Extreme Puzzle No.6

urhegyi wrote:Or thisone which is essentially the same:
Code: Select all
`.4.1..9....2..8.1.....3.8.2.1.8..5.............5..6.9.3.6.2.....9.6..3....1..9.7.`

It is exactly the same, a renumbered isomorph.

m_b_metcalf
2017 Supporter

Posts: 11448
Joined: 15 May 2006
Location: Berlin

Re: Extreme Puzzle No.6

Code: Select all
`.4.|1..|9....5|..8|.1....|.2.|8.5---+---+---.1.|8..|3.....|...|.....3|..6|.9.---+---+---2.6|.5.|....9.|6..|2....1|..9|.7.`

My usual map of givens per box:
Code: Select all
`| 2 | 3 | 4 || 2 | 2 | 2 || 4 | 3 | 2 |`

This suggests central or diagonal symmetry. Diagonal symmetries are not possible (4 digits an the main diagonal; 6, 8 on the second diagonal not compatible in boxes [19].
Central symmetry is present on the givens with the digit permutation [19] [25] [3] [47] [68] => +3 r5c5

The puzzle rating is lowered to SE 9.2, still hard to solve.
Cenoman
Cenoman

Posts: 1576
Joined: 21 November 2016
Location: Paris, France

Re: Extreme Puzzle No.6

I got the rotational symmetry and solved 7 cells with reasonable chains. After trying all the usual suspects I'm guessing that there might be a Senior Exocet, which I don't do.

Leren

PS I had one more trick up my solver's sleeve. It found an Exocet r5c4 r5c6 r4c3 r6c7 2457 which solves the puzzle, but it required what I call a full digit expansion to prove it, so I am reluctant to use it.

Leren
Leren

Posts: 4006
Joined: 03 June 2012