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PostPosted: Sat Apr 04, 2009 4:13 am 
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Grand Master
Grand Master

Joined: Wed Apr 23, 2008 6:04 pm
Posts: 1893
Location: Lethbridge, Alberta, Canada
WELCOME!!

This is an edited version of the advice message that I first posted on Ruud's website; it has been updated to make it appropriate for this site. I've used the abbreviation A for Assassin in this message; it's become the standard form since Assassins moved to this site.

Many thanks to Afmob, Ed and Para for their helpful feedback when the original advice message was updated and expanded, and particularly to Ed for all the encouragement that he's given to me and for significant parts of the original message and the updated version on this site. Thanks also to Ruud for making this message a "sticky" on his site and to Richard for doing the same on this site.


Since the title of this message is advice, here it is

1. Don't be afraid to try Assassins! If you are a newcomer to Killers the first twelve Assassins are good ones to start with; they are available in Archive A. The following is also a good selection to start on, some of them are easier than the early Assassins :- Twosome 1 to Twosome 6, A125V0 Newbie Killer, A118V0.9 (the second diagram), A123V0.9 (hidden diagram near the end of the post), A150 which Ronnie G posted saying "Thought this was a good time to return to our roots, with a simple(r) puzzle, to entice the newer members and our guests!", A180V0.1 (please don't be put off by the fact that this one has some disjoint cages, they don't make it difficult), A182V0.1 (you can then progress to A182V0.2), A184-Lite (the lower diagram) and the puzzles in the Messy One series are also good starting ones; please note that A175V0.25 is not a beginner's puzzle. If you feel like trying one that's really messy but not difficult, try The Messier, The Merrier 1, They all have posted walkthroughs in case you get stuck!

Some Assassins are Killer Xs, where the numbers on both diagonals have to be 1-9. Good starting one are Twosome 7 and Twosome 8 and A179V0.90; then once you've solved that one you can try it again as a regular killer A179V0.96. If you find these a bit harder, I've given a hint in the introduction to my walkthrough for A179V0.90. Twosome 7 and Twosome 8 can also be solved as regular killers.

Another interesting one which you might like to try is Anti-King Killer. It's like a regular killer with the extra restriction that diagonally adjacent cells can't contain the same value. If you enjoy that one, you might also like to try Assassin 252 V0.8 which has the extra restriction of a Girandola group, which must contain each of the values 1 to 9.

In addition to puzzles in the Killer forum, there are many interesting puzzles in the Other Variants forum, some of which are variants of Killers.

2. If a puzzle has introductory comments you should read them; they may provide helpful hints.

3. There are two main approaches for solving killers; insertion solving where you put in information as you work it out and elimination solving where you start with all candidates 1-9 in each cell and gradually eliminate them. It is strongly recommended that you should use elimination solving for all puzzles on this site. Most posted walkthroughs use it.

4. Write a walkthrough while you are solving each Assassin, even if it's only notes on scraps of paper; I do mine in a Word file while I'm solving the puzzle.

5. After you have solved an Assassin, or at least tried to solve it, read the walkthrough(s) that are posted on this forum. It's good to see how other members of the forum have solved puzzles and if you work through the posted walkthroughs you should learn some techniques. Some walkthroughs are basically how a puzzle was solved; other walkthroughs try to show the most direct route to solve the puzzle. The next two messages in this thread provide more detail about how Ed and I write walkthroughs.

6. Many people on this forum use Sudoku Solver which is available as a free download from the Software Forum, SumoCue from Ruud's website and/or JSudoku from J-C's site. Most puzzles have a code string that can be directly imported into these solvers.

7. There are also other harder variants of some Assassins and some other puzzles posted on this forum. Once you have solved a few Assassins, you might like to try Ruud's Chevron Killer, Nasenbaer's NonCon and CDK; these are all in Archive A. The other ones are generally much harder but are worth trying when you have gained more experience.

8. Once you have become confident and are solving the current puzzles, please join the forum and post your walkthrough if you are the first for a puzzle or if you have a significantly different solving path, particularly if it avoids difficult steps. Most of the regulars on this forum first posted walkthroughs here. Some of the early ones are a mess and hard to read, but with feedback and lots of practice, they get easier. Start!

Regular walkthrough posters often give their rating for how hard they found it to solve each puzzle, based on Mike's definitions here. There's no need to do this until you have gained confidence from posting your walkthroughs.

9. If you post a walkthrough while a puzzle is still active (before the next Assassin has been posted or 7 days for variants and other puzzles), please use tiny text or hidden text. The Font Size for Tiny sets Size = 50. In the text area you should then change this to Size = 14, then type or paste your walkthrough between the two sets of []. If you use hidden text, it is helpful to give an indication of the length of your walkthrough in the hidden text header. After the puzzle has been posted for at least 7 days, if you have used tiny text you should delete the tiny text commands to convert your walkthrough to normal text.

See below, in the section Solutions, how to produce hidden text with a header.

10. Enjoy the challenge of Assassins and have fun!

11. Don't be afraid to contact regular posters to the Assassin forum by using the Private Message (PM) facility. This is a very friendly forum and people are very helpful.

12. You need to be a registered member and to have signed in to be able to reply to messages on the forum or send private messages to other forum members. Registration is a simple process. It includes a user profile. That can be edited at a later date.


The best feedback I received while working on an earlier update was "I guess I just adapt to the forum". An excellent suggestion!


Now to some more detailed descriptions of how this forum works.


Walkthroughs

A walkthrough should be easy to follow for a newbie to Killers. Some people give more detail than others - it's a matter of personal preference. The important thing is that it is easy to follow. Preliminary steps are usually given unless you state that they have been omitted or there is a candidates diagram.

Try to avoid putting too much into preliminary steps. Simple combination clashes, locked candidates for rows/columns/nonets and common peer eliminations seem to be acceptable. Killer pairs and more complicated combination clashes should be given as separate steps after the preliminary ones.

One good suggestion, received in response to the draft that I posted on the forum was "I always try to use my preliminaries to set the grid to what SumoCue shows you when you open marks. That is why I tend to keep the locked candidates till the end of the prelims (like 17(2) or 23(3) cages). I guess I like to keep things as simple as possible in the beginning. Otherwise you have to start with awkward notations like [18/27]/{36/45}".

Include clean-up effects resulting from candidate eliminations in other cells; don’t assume that someone going through your walkthrough will do them ‘automatically’.

Walkthroughs usually end when singles have been reached. It's a matter of personal preference whether to stop at naked+hidden singles or at naked singles. There's no need to continue until all cells have been fixed.

A walkthrough should be your own work - not software solver aided. If a solver gave you some help or showed a shortcut at a certain spot, say that the solver did that.

The creator of the puzzle doesn't publish their own walkthrough unless other players have failed to solve the puzzle or haven't posted a walkthrough. Even when the puzzle is no longer active, the puzzle creator will only post detailed comments or a walkthrough when there is something interesting that hasn't been covered by other players' walkthroughs.

My personal opinion is that all Assassins and all forum puzzles ought to have posted walkthroughs. We know we have too many puzzles active if one doesn't get a walkthrough.

If you find a mistake in a solver's walkthrough, and it makes the solution invalid, point this out by private message (PM) or on the forum (*). We all want to know! If you can see a valid way to get around the problem, suggest that too. If you notice any small errors, point those out by PM. If there is something you liked - tell them...or even better, tell everyone on the forum!

Where feedback has been provided by PM and used for editing it's good 'netiquette' to give credit except for minor points such as typos.

(*) If a solver asks for feedback to be sent by PM, rather than on the forum, please respect this. In return the solver should be prepared to post any important points made in the feedback.


Walkthrough Notation

There is no specific way to write walkthroughs. We each have our own styles which, in my opinion, makes this forum more interesting.

All steps should be numbered. There should be a blank line between numbered steps but not within a sequence of sub-steps. It is a matter of personal preference whether to number the preliminary steps or to give them as a group at the beginning and then start numbering after that.

Rows, columns and nonets are usually identified using the letters R, C and N (in either upper or lower case according to personal preference) followed by a number or numbers, for example R1C23.

Cages which are within one row, column or nonet are normally identified by their cells or by the nonet. Other cages that are in more than one nonet are identified either by their upper-left cell (the cell which contains the cage total in the puzzle diagram), for example 21(4) cage at R6C8, by the cells they are in, for example r6c8+r7c78+r8c8, or by the nonets they are in, for example 21(4) n69.

Where there are two similar cages in the same part of the grid, for example A68 has a 19(3) cage completely in N6 and another at R6C9 that is partly in N6, it is clearer to refer to both cages by their cells.

When listing the options for a cage, partial cage or split cage, {} is used to list options where the order of the candidates is not known. [] is used where the order of the candidates, or some of the candidates, is known. When using [] for multi-row or multi-column cages, the candidates should be listed from left-to right, top-to-bottom.

{} and [] can both be used in a list of options where the order of some of the candidates is known.

When listing options for a cage, alternatives should be separated by / or |. Other separators such as the letter I should not be used; they can make it really difficult to read a walkthrough. My personal opinion is that /, rather than |, makes it easier to read a set of combination options.

When candidates are locked for particular cells, for example because of a Naked Pair, this should be indicated by saying "locked for …" or "not elsewhere in … (sometimes abbreviated as n/e)".

When a value is fixed in a cell, you should not say "not elsewhere in row/column/nonet". An exception is for Killer-Xs where some walkthroughs will say "placed for D/" or "placed for D\"; earlier walkthroughs used "locked" but "placed" is preferable.. An alternative might be to say at the beginning of the walkthrough "Remember to eliminate candidates when cells on one or both diagonals are fixed". When working through a walkthrough with an automated solver in editing mode, these eliminations will be made automatically. However not everyone uses an automated solver.

-> is used to indicate that something follows from the previous action, when there is a string of things they are often separated by commas.

Some walkthroughs use <>, meaning "does not equal", to indicate that a value has been eliminated from a cell or a combination/permutation has been eliminated from a cage. The other normal method is to give eliminations in words, for example no 8 in R2C4.

The use of [] after a set of combination options, for example {149/167/248} = [1/2, 4/6, ...], shows alternatives that must be present in the cage. These are useful when a later step eliminates combinations from other cages that clash with these alternatives. If the alternatives are not used later, they aren’t normally listed. In the example 1/2, 4/6 will be used later; ... indicates that other alternatives won't be used.

A good web page for further explanation of notation is Killer Lingo. However some of the notation used on that page is not consistent with this forum and should be avoided. For example describing a cage as 21/4, rather than the normal 21(4), is confusing because it suggests an alternative.

If you use advanced techniques, particularly if they are expressed in Eureka notation, make sure that the result(s) of these steps are clearly stated so that people who don’t know these techniques can understand what has been done and, if they wish, try to work out that step by alternative methods.


Killer Terms

Terms commonly used in walkthroughs (with their abbreviations, where used on this forum) include

Naked Single (NS), Naked Pair (NP), Naked Triple (NT), etc.
Hidden Single (HS), Hidden Pair (HP), etc.
Killer Pair (KP), etc.
45 rule, Innies, Outies, Innies/Outies (O-I is used to specifically mean Outies minus Innies)
Common Peer Elimination – (CPE).

More advanced techniques are appearing more often in walkthroughs as puzzles get harder and solvers better. The more common ones include X-Wings and Law of Leftovers (LOL).

Innie and Outie Unequal (IOU), see this message.

Ruud has an excellent Glossary of Sudoku terms on his website.

Some of the more interesting techniques are included in the Killer Techniques forum.

If you come across terms in walk-throughs that should be included here, please let me know and I'll edit them in. We want everyone, especially those new to killers, to understand!


Diagrams

All posted puzzles should have a diagram. If you post a variant and can generate the code string but not a diagram, please ask for a regular to post a diagram.

Some puzzles are also posted with candidate diagrams. If you do this, please post the candidate diagram below the puzzle diagram. Posting diagrams side by side widens the forum thread and can make it difficult to read other messages in the thread.


Solutions

Puzzle creators on this site post the solution under the diagram when the puzzle is posted. Earlier puzzles on this site gave the solution in tiny text but many puzzle creators now use hidden text. In my opinion hidden text is preferable and, where possible, a grid as in the solutions for Ed's puzzles; they make it much easier to read and check one's solution. Ed has told me that you can make the grid easily using JSudoku (Open the puzzle; Solve -> Recursively solve, followed by Edit -> Copy candidates; paste into message).

You can use the hide button to give hidden text. This will give you the following.

Hidden Text:
This is hidden text.
Some people prefer to have their own header for the hidden message, rather than just Hidden Text. A bit more work is needed to do this but IMHO it's worth the effort.

Click on the hide button. Insert the text that you want to hide between the two command strings. Then in the first command string replace the word hide with collapse=your header and in the second command string after / replace hide by collapse. Make sure that you don't use any "quotation marks", bold text or underlined text anywhere within either command string.

As an example
Solution:
This is the puzzle solution
You can see the command codes for this example if you click on the quote button at the bottom of this message and then scroll down to the Solutions section.


Variants

Variants provide harder, or less often easier, versions of a puzzle. There are two main types of variant.
1. The same cage pattern with different cage totals and therefore a different solution.
2. Modified cage pattern with the same solution.

Variants of Assassins should only be posted if someone has signed up for the next Assassin; this is to encourage the regular provision of Assassins each week.


Solvers

Manual solving is what this forum is about. Software solver/helpers have a place, but always say when they have helped. They are generally a last resort.


Messages

Newcomers to the forum should remember to read the messages in their Inbox. They may receive replies to forum messages by private messages. If you are signed in, the header area of any forum page will tell you if you have any new messages.


Finally, something that has largely gone from this forum.

TAG Solutions

The original idea for tag solution was - "the 'tag' being like in 'tag-team' wrestling - one person starts, then another takes over".

Basically, the unwritten 'rule' is that as soon as one forum member publishes a partially-completed puzzle, asking for assistance, he or she is implicitly starting off the tag. The idea then is for someone else to pick up the tag and 'run' with it.

Wait until a tag solution is finished before posting an individual walkthrough.

The puzzle creator will only take part in a tag solution if they don't know how to solve it. However they may post hints if the tag seems to be getting stuck.


Last edited by Andrew on Sun Jan 06, 2013 11:07 pm, edited 11 times in total.

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PostPosted: Sat Apr 04, 2009 4:30 am 
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Grand Master
Grand Master

Joined: Wed Apr 16, 2008 1:16 am
Posts: 1039
Location: Sydney, Australia
Thanks for doing this again Andrew! Great to see our culture in black and blue.

As Andrew promised, here are some thoughts on how I write a walkthrough. This message originally came from here. I hope it doesn't discourage you from having a go at one. Thanks to Andrew for the suggestion to post it here as well.

Andrew wrote:
What is an optimised WT? Is it the most direct solving path, which may use technically harder and therefore higher rated steps, or is it a longer path that uses the lowest possible rated steps?
Probably more the second for me, though that may still use much harder steps than another walkthrough. In practice optimising my walkthrough works like this.

1) Solve the puzzle once keeping rough notes

2) Think backwards from the first placement to guess which steps (in that area of the puzzle) were essential to achieve that first placement.

3) Solve it again, ticking those parts of the notes that help get to the first placement as directly as possible. Put brackets around the parts that don't appear to help.

4) While doing that, find simpler ways to do steps. Keep notes...possibly heading off into a completely new direction with something important missed the first time.

5) Work backwards from the second placement, then the 3rd etc.

6) Think about whether the 2nd placement could be more important than the 1st placement and can get to it straight away without the first placement. etc

7) Finally, get a clear picture in my mind of the whole solving path.

8) Type the WT. That can change the solution again if something new is found.

9) Check the WT

10) Triple check the WT and hope you don't find anything new!!

11) Decide how difficult that whole process was to keep "in the head". What rating does that feel like? 24 steps before I get to stop thinking feels like a 1.25 rating to me. Usually, 1.0 rated puzzles are around 5-15 with the remainder just getting it to singles.

Of course, deciding on the most difficult move also influences the rating. A very short WT with one difficult step still gets that steps rating. With JFFK3 I chose to go the longer route to get the lower rating.

12) Read other's WT to find what you missed.

Time consuming process but very satisfying when it's an interesting solution. But no wonder we don't get many new WT writers!

Cheers
Ed


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PostPosted: Sat Apr 04, 2009 4:36 am 
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Grand Master
Grand Master

Joined: Wed Apr 23, 2008 6:04 pm
Posts: 1893
Location: Lethbridge, Alberta, Canada
Wow! That's impressive! Several others, including some who aren't currently regulars, post optimised walkthroughs; Afmob is also often the first to post a walkthrough.

My walkthroughs are different. Originally they were how I solved the puzzle. Then I decided that when I spotted something that I really felt I ought to have spotted earlier, I would put that step in the proper place and rework the steps after that.

Very occasionally I'll do a complete restart, for example in JFFK1 where I didn't spot the initial key step until after manu had commented to me about JFFK3.

JFFK3 was one where I did some rework but only before moving on to the next step. At first I saw step 3 as 3(2+1) outies but felt from the SS score that there might be something better so I looked more carefully and found 3 innies and 1 outie, which was also a much more productive step.

I always try to do Ed's final step, read any existing posted walkthroughs, and most times manage to do this before I post my own one.

Whether your preferred approach is to optimise your walkthrough or to write it more like you solved it, please consider posting your walkthrough. Most puzzles deserve at least two walkthroughs and more if the extra ones have something interesting to add.


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