The New Sudoku Players' Forum

[hellen4you]

i play the classic one and i want to try something new so tell me ...

[Agrajag]

Killer.

A whole new world will open up. Much less repetitive than the standard sort.

The Times publishes one everyday

Otherwise search for killer sudoku and you fill find loads

[LadyGrace]

Jigsaw. That's my favorite variation. It's a lot of fun. Plus there are so few books on it.

[Bigtone53]

Killer. No competition for a daily workout without spending the whole day on it. As Angrajag says, The Times in the UK does one daily (available online) with an expected solving time which increases through the week to 1 hour+ on Fridays. Just right for the commute by train

[EmmaG1959]

Killer is amazing. I get bored with the ordinary ones (even when I can't solve them!). There's a great site (www.killersudokuonline.com) which publishes one every day. Their Extreme, Outrageous and Mind Bending versions are much harder than the Times Deadly, and the last 2 categories I haven't yet solved a single one.

[Bigtone53]

There's a great site (www.killersudokuonline.com) which publishes one every day. Their Extreme, Outrageous and Mind Bending versions are much harder than the Times Deadly, and the last 2 categories I haven't yet solved a single one.

EmmaG, that is what is called a challenge. I will get to it and to hell with the day job!

[Pat]

There's a great site (www.killersudokuonline.com) which publishes one every day. Their Extreme, Outrageous and Mind Bending versions are much harder than the Times Deadly, and the last 2 categories I haven't yet solved a single one.

EmmaG, that is what is called a challenge. I will get to it and to hell with the day job!

why even try --
do you know what it takes to solve one of those ??

even in SuDoku,
there are plenty of puzzles which are just Too Tough for me

but there at least i have the option of
pre-screening the puzzles with e.g. gsf's software
to get an idea of the true level of difficulty,
then if the software tells me it's Too Tough ( by my own standards ),
i'll skip that puzzle---

[Bigtone53]

Pat wrote

why even try

Why so negative? I looked at Weekly 120, described as mind-bending and although it involved a couple of eliminations thorugh URs, this was easily the job of a lunch hour.

EmmaG

Are the extreme and outrageous ones harder than mindbending?

[Pat]

why even try

Why so negative?
I looked at Weekly 120, described as mind-bending and although it involved a couple of eliminations thorugh URs, this was easily the job of a lunch hour.

thanks!

now that you have solved one,
we have some estimate of the level of difficulty
implied by their "mind-bending" rating

[Bigtone53]

now that you have solved one,
we have some estimate of the level of difficulty
implied by their "mind-bending" rating

Not really, unless you know how good I am, but I suspect that I am pretty useless!

By the way, the reference to URs was probably incorrect and should have been to BUG1

[udosuk]

If you guys are into extraordinarily hard Killer Sudoku puzzles, try Frank's #58, available from this page:

http://members.shaw.ca/fdkr2/

... or more specifically, from this link:

http://members.shaw.ca/fdkr2/fdkr058.png

[EmmaG1959]

Are the extreme and outrageous ones harder than mindbending?

I think it goes Easy, Moderate, Hard, Extreme, Outrageous, Mind Bending

They also have 'greater than' killer sudokus, but life is too short. At least mine is!

Glad to learn that they aren't really that hard. Not that I understand any of the solving technique terms... I can't cope with reading the 'techniques for solving' that get posted, so I just go my own way. I'm probably missing something!

Today (25/04/2008) I can't even get far with the Hard, and my lunch break will soon finish.

[Jean-Christophe]

I'm too a fan of killer

Here are some sites publishing killers on a regular basis:

Rather easy:
The Times Online
sudoku.org.uk. Even the weekly "Extreme" are easy, nothing as hard compared to their vanilla and jigsaw extreme.

Harder:
djape.net. Also hosts a good forum where messages are mostly related to killer
Killer sudoku online

Very hard:
sudocue.net. Ruud used to publish very hard weekly killers, but he seems to have lost interset in sudoku. Anyhow, forum members continue to publish very hard weekly killer.

See also my blog for other links and the notation / lingo commonly used for walkthroughs.

1. 23/3 @ r8c234 = {689} (NT @ r8)

2a. 45 @ r6789 -> r6c78+r7c7 = 23 = {689}, r5c89 = 11 = {47} (NP @ n6, r5)
b. 45 @ r5 -> r5c12 = 12 = {39} (NP @ n4, r5, 27/5)
c. -> 27/5 @ n14 = {39..}

4a. 10/4 @ n47 = {1234} -> 3 locked @ r7c23 for n7, r7
b.10/3 @ c1 <> {136|235} = {127|145}
c. Both 10/3 & 10/4 must include 1 either within n7 or n4 (or r6)
d. This forms an X-Wing -> 1 locked for n47, r6
Note: such X-Wing are quite frequent in KSO killers

5a. 8/3 @ n9 = {1(25|34)} -> 1 locked for n9
b. 15/4 @ n69 = {2346} (cannot have 1)
c. NQ -> r89c9 <> {2346} = {15} (NP @ n9, c9)
d. 8/3 @ n9 -> r9c8 = 2
e. 15/4 @ n69 -> r6c9 = 2, r8c8 = 3, r7c89 = NP {46} @ n9, r7
f. r8c7 = 7 (NS @ n9)
g. r79c7 = NP {89} @ c7 -> r6c7 = 6

6a. 10/4 @ n47 = {1234}
b. r6c23 = NP {14} @ n4, r6, 10/4
c. r7c23 = NP {23} @ n7, r7

7a. 11/4 @ n36 = {1235}
b. r34c7 = [23], r34c8 = NP {15} @ c8
c. r4c8+r5c7 = HP {15} @ n6

8a. 13/2 @ r67c4 = {58} (NP @ c4)
b. 12/2 @ r34c4 = [39]
c. r8c4 = 6, r8c23 = NP {89} @ n7
d. 45 @ n7 -> r6c1 = 5 (since r6c23 = {14} = 5)
e. 10/3 @ c1 -> r78c1 = [14]
f. 13/2 @ r67c4 = [85], r6c8 = 9, r7c7 = 8, r9c7 = 9
g. 26/4 @ r89c6 -> r89c6 = [28]
h. r8c59 = [15], r9c9 = 1
i. 10/2 @ r67c6 = [37], r67c5 = [79], r9c45 = [43]
j. 6/2 @ r34c6 = {15} (NP @ c6)
...

Hope this helps

NB: Don't try the particular one mentioned by Matt (udosuk). I'm not even sure he is able to solve it himself ;) However, other killers created by Frank are really enjoyable.

[Jean-Christophe]

By the way, the reference to URs was probably incorrect and should have been to BUG1

Uniqueness techniques are not required to solve KSO killers. I've never used BUG+1 and I doubt it is applicable in most killers.

This sounds like you are not aware of the restrictions to all uniqueness techniques for killer. For instance in KSO Weekly 120, one cannot use UR for r12c14, nor any other rectangle with r12c1 because r12c1 are in two different cages and therefore do not form a valid dealy cycle. One cannot swap the digits in r12c1 in the solution because it would give another sum for the cages. The only valid rectangles for r12 are in c4569. Any other rectangle in r12 with any column in c12378 cannot be used for UR. As an example: the solution for KSO Weekly 120 has r12c5 = [78] and r12c8 = [87] which is not a deadly pattern since r12c8 are in different cages.

In particular, one cannot plug in the candidates of a killer into a software for vanilla sudoku and seek for uniqueness techniques, because it is unaware of the restrictions imposed by the killer and may report deadly patterns which are indeed not deadly.

[udosuk]

NB: Don't try the particular one mentioned by Matt (udosuk). I'm not even sure he is able to solve it himself ;) However, other killers created by Frank are really enjoyable.

Yes, you're right I can't solve it myself. Not even your JSudoku can solve it by itself logically. But jointly working with JSudoku I do know a cheap way to crunch out the solution in a few minutes without "Recursively Solving":

1. Load the PS Code into JSudoku, from this file.

2. Try to set 14/2 @ r67c7={68} and press Ctrl-Shift-V (Check Grid Validity) => No Solution. So set it to be {59} and press Ctrl-Shift-V => Unique Solution. Thus r67c7={59} (NP @ c7).

3. Now 7/2 @ r45c7={16|34}. Try set it to be {34} and press Ctrl-Shift-V => No Solution. So set it to be {16} and press Ctrl-Shift-V => Unique Solution. Thus r45c7={16}.

4. Set r4c7=1 and press Ctrl-Shift-V => No Solution. Set r6c7=5 and press Ctrl-Shift-V => No Solution. So set r4567c7=[6195] and press Ctrl-Shift-V => Unique Solution.

5. Now press Ctrl-Shift-D (Deduce All Moves). Voila! After a rough workout on the CPU the grid is solved, with the following moves applied:

70 Naked Singles
7 Hidden Singles
3 Unique Pairs
2 Naked Pairs
2 Hidden Pairs
1 Naked Triplets
12 Intersections
13 Odd Pairs
1 Generalized Hidden Pairs
11 Odd Triplets
2 Double Innies & Outies
15 Mandatory Inclusions
10 Odd Quads
12 Complex Intersections
4 Triple Innies & Outies
4 Double Outies minus Innies
5 Complex Naked Pairs
10 Complex Hidden Pairs
11 Conflicting Pairs
10 Quadruple Innies & Outies
5 Triple Outies minus Innies
1 Pointing Pairs
1 Unique Combinations
5 Odd Combinations
1 Pointing Triplets
2 Locked Cages
6 Conflicting Triplets
1 Turbot Fishes
1 Grouped X-Wing
5 Grouped Turbot Fishes
3 Grouped Turbot Chains with 5 links
5 Grouped XY-Chains up to 3 links
87 Conflicting Partial Pairs
10 Multiple Innies & Outies
1 Multiple Split Cages
11 Multiple Outies minus Innies
4 Multiple Overlaps
9 Complex XY-Chains up to 3 links

I guess we can call it "manual recursive solving"... Just don't ask me to follow all those XY-Chains and "Partial Pairs"...