The New Sudoku Players' Forum

[Henke_a_]

Hey,

This puzzle has been bothering me for quite a while. I usually solve them without too much trouble but this one... I can't seem to figure out how to advance. Would really appreciate some help (with explanation/reference to strategy). So far the puzzle is correct, according to the program.

It's an extreme+ puzzle, and I am using the sudoku app from genina.com.

Cheers,
Henrik

[SteveG48]

Code: Select all

 *-----------*
 |.6.|1.8|3.5|
 |5..|.4.|861|
 |81.|5.6|4..|
 |---+---+---|
 |279|61.|58.|
 |6.8|259|71.|
 |.51|.8.|692|
 |---+---+---|
 |.85|4.1|.36|
 |1..|.6.|.58|
 |..6|8.5|147|
 *-----------*


Look for a two string kite on 2's and then an empty rectangle on 3's. There's no special strategy here- just look for eliminations until the puzzle gives up the ghost.

[eleven]

Alternatively kite and finned x-wing in 9 and skyscraper in 3.
Or finned x-wing (aka grouped skyscraper) in 9 and skyscrapers in 2 and 3.

[Kristoforus]

Hi
To completly solving this puzzle i used 2 strategies 3 times forcing chain (AIC) and at end Medusa 3D
In notation i use letters from A to I for rows and digits 1-9 for columns.
Lets start.
Firs chain is:

IF -7B3->+7(B 3/6)-> -7(A/C5)->+7G5->-2/9 G5->+2G7->-2H7->+9H7->-9H4->+9J5->-9A5->+9A1-7A1->+7B3 if 7 is removed from B3 chain implies tha must be. Other candidates in B3 must be false.
After all possible elimanations in G1 is last candidate 7 in col 1 so he must be true.

Second chain is:

If -3J1->+9J1->-9A1->+4A1->-4A3->+2A3->-2A8->+2C8->-7C8->+7C5-3C5->+3J5->-3J1
So we have continous loop this chain implies this eliminations: -2A5 -2C5 -3J2 Now in B6 is last cand 2 so must be true In A/C3 is pointing par 2 after all possible eliminations ( im not telling about all of them everyone must find by self) next step.

Thirth and last chain is:

IF -2J2->+9J2->-9J1->+9A1-4A1->+4A3->-4H3->+4H2->-2H2->+2J2
IF 2 removed from J2 chain emplies that must be.

Now after all possible elimintiions diagram should have about 20 unsolved cells and in most of them only 2 candidates so now is best moment for medusa3d. If someone dont khow what is it .....well in internet is all.
Medusa leds to contradiction in cell H2 and in this same momemnt we khnowing true values for 95% unsolved cells . Medusa3D is super
Ok thats all i hope is no mostakes in chains notation if are sorry:)
Enjoyed