dailysudoku.com :: View topic - Hard puzzles: A new source?

dailysudoku.com
Discussion of Daily Sudoku puzzles

FAQ

Memberlist

Usergroups

Profile

Hard puzzles: A new source?
Goto page Previous 1, 2, 3 Next

dailysudoku.com Forum Index -> Other puzzles

View previous topic :: View next topic

Author

Message

keith

Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

Posted: Wed Oct 26, 2011 1:35 pm Post subject:

On this site, "hard" means naked or hidden set. I believe the Oct 19 has three doubles. Keith

Pat

Joined: 23 Feb 2010
Posts: 207

Posted: Wed Oct 26, 2011 2:08 pm Post subject:

keith wrote:

On this site, "hard" means naked or hidden set. I believe the Oct 19 has three doubles.

it needs just 1 double

in the above discussion, i got the idea that a double is Medium, Hard meaning triple or larger

arkietech wrote:

Medium to me requires a pair or pairs
but not triples or higher

arkietech

Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

Posted: Wed Oct 26, 2011 2:35 pm Post subject:

Pat wrote:

keith wrote:

On this site, "hard" means naked or hidden set. I believe the Oct 19 has three doubles.

it needs just 1 double

in the above discussion, i got the idea that a double is Medium, Hard meaning triple or larger

arkietech wrote:

Medium to me requires a pair or pairs
but not triples or higher

I have worked "medium" puzzles for years from many sources. They all have NAKED doubles but not triple or higher. Never a HIDDEN double. to me a hidden double is the same and often coexists with a triple or quad.

I do not know the rules of this site.

Pat

Joined: 23 Feb 2010
Posts: 207

Posted: Wed Oct 26, 2011 2:44 pm Post subject:

okay, eventually i'll figure it out

Daily Sudoku wrote:

Very Hard

Code:

+-------+-------+-------+
| . 3 . | 2 . . | . . 1 |
| . . 8 | . . . | . . 4 |
| . 7 4 | . 3 . | 9 6 . |
+-------+-------+-------+
| . . . | 1 8 . | . . 7 |
| . 1 . | 6 . 9 | . 3 . |
| 8 . . | . 7 5 | . . . |
+-------+-------+-------+
| . 4 1 | . 6 . | 8 9 . |
| 7 . . | . . . | 4 . . |
| 9 . . | . . 3 | . 7 . |
+-------+-------+-------+

Play this puzzle online at the Daily Sudoku site

here too, triple not needed
-- but the "hidden" double makes it VH ?

arkietech

Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

Posted: Wed Oct 26, 2011 3:14 pm Post subject:

Pat wrote:

okay, eventually i'll figure it out

-- but the "hidden" double makes it VH ?

No--to me it is a Hard. A Very Hard requires an advanced move.

arkietech

Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

Posted: Wed Oct 26, 2011 4:30 pm Post subject: Today's medium puzzle

Code:

*-----------*
|.3.|.2.|.5.|
|4.2|3..|7..|
|7..|8..|...|
|---+---+---|
|..1|...|.3.|
|.7.|1.3|.9.|
|.5.|...|2..|
|---+---+---|
|...|..5|..3|
|..8|..4|5.7|
|.6.|.1.|.4.|
*-----------*

*--------------------------------------------------------------------*
| 68-19 3 69 | 4679 2 1679 | 14689 5 4689 |
| 4 189 2 | 3 5 169 | 7 168 689 |
| 7 19 5 | 8 469 169 | 3 126 2469 |
|----------------------+----------------------+----------------------|
| 68-9 89 1 | 5 7 2 | 468 3 468 |
| 2 7 46 | 1 468 3 | 468 9 5 |
| 3 5 469 | 469 4689 689 | 2 7 1 |
|----------------------+----------------------+----------------------|
|x19 4 7 | 269 689 5 | 1689 1268 3 |
|x19 2 8 | 69 3 4 | 5 16 7 |
| 5 6 3 | 279 1 789 | 89 4 289 |
*--------------------------------------------------------------------*
From today's "medium" puzzle

Pat

Joined: 23 Feb 2010
Posts: 207

Posted: Wed Oct 26, 2011 4:41 pm Post subject: re: 2011.Oct.26 -- Medium

re: 2011.Oct.26 -- Medium 1 move -- either (9) b5\r6 or (9) r4\b4

Pat

Joined: 23 Feb 2010
Posts: 207

Posted: Wed Oct 26, 2011 5:03 pm Post subject: "Meister Sudokus" puzzle 40

.6...4.......2....3.58....765...7.9..4.....2..7.1...364....69.1....8.......5...8.

[ play ]

Code:

+-------+-------+-------+
| . 6 . | . . 4 | . . . |
| . . . | . 2 . | . . . |
| 3 . 5 | 8 . . | . . 7 |
+-------+-------+-------+
| 6 5 . | . . 7 | . 9 . |
| . 4 . | . . . | . 2 . |
| . 7 . | 1 . . | . 3 6 |
+-------+-------+-------+
| 4 . . | . . 6 | 9 . 1 |
| . . . | . 8 . | . . . |
| . . . | 5 . . | . 8 . |
+-------+-------+-------+

keith

Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

Posted: Wed Oct 26, 2011 10:57 pm Post subject: Re: "Meister Sudokus" puzzle 40

Pat wrote:

.6...4.......2....3.58....765...7.9..4.....2..7.1...364....69.1....8.......5...8.

[ play ]

Code:

In my book, "hard". Can be solved by hidden singles only, no sets.

If you want to grade puzzles simply by techniques needed, that's what you get.

Keith

Marty R.

Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

Posted: Wed Oct 26, 2011 11:07 pm Post subject:

I did the puzzle, but haven't a clue as to rating. I needed Multi-coloring (extension of Skyscraper); r7c3<>7=8.

keith

Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

Posted: Thu Oct 27, 2011 2:40 am Post subject: Re: "Meister Sudokus" puzzle 40

keith wrote:

Pat wrote:

.6...4.......2....3.58....765...7.9..4.....2..7.1...364....69.1....8.......5...8.

[ play ]

Code:

In my book, "hard". Can be solved by hidden singles only, no sets.

If you want to grade puzzles simply by techniques needed, that's what you get.

Keith

Nice puzzle. No advanced moves or sets.

Did it without pencilmarks, but it helped that I knew advanced moves were not required.

The key is to figure out R7C3.

Keith

Marty R.

Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

Posted: Thu Oct 27, 2011 4:53 pm Post subject:

After Keith's post I had to do it again and didn't need advanced moves, although it's way too difficult for me to do it without pencil marks.

arkietech

Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

Posted: Thu Oct 27, 2011 5:50 pm Post subject: Re: "Meister Sudokus" puzzle 40

keith wrote:

In my book, "hard". Can be solved by hidden singles only, no sets.

How do you handle this with no sets?

Code:

*-----------------------------------------------------------*
| 278 6 278 | 379 357 4 | 358 1 3589 |
| 178 18 4 | 379 2 35 | 358 6 3589 |
| 3 9 5 | 8 6 1 | 2 4 7 |
|-------------------+-------------------+-------------------|
| 6 5 238 | 23 34 7 | 1 9 48 |
| 189 4 1389 | 6 359 358 | 7 2 58 |
| 289 7 289 | 1 459 258 | 458 3 6 |
|-------------------+-------------------+-------------------|
| 4 28 28 | 237 37 6 | 9 5 1 |
| 5 123 1269 | 4 8 239 | 36 7 23 |
| 279 23 2679 | 5 1 239 | 346 8 234 |
*-----------------------------------------------------------*

A great puzzle! to me some naked singles are very hard.

Marty R.

Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

Posted: Thu Oct 27, 2011 6:27 pm Post subject: Re: "Meister Sudokus" puzzle 40

arkietech wrote:

keith wrote:

In my book, "hard". Can be solved by hidden singles only, no sets.

How do you handle this with no sets?

Code:

A great puzzle! to me some naked singles are very hard.

Dan, I'm not sure I understand your question. Are you challenging the reader to do the puzzle without using that 28 pair in r7? Also, what is a naked single? To me it sounds like a solved cell?

Quote:

In my book, "hard". Can be solved by hidden singles only, no sets.

May I assume that a set is a naked pair, triple, quads, etc? If that is the case, don't hidden singles (or hidden pairs, etc.) have complementary sets? So how could one use a hidden single without using a set?

arkietech

Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

Posted: Thu Oct 27, 2011 8:06 pm Post subject: Re: "Meister Sudokus" puzzle 40

Marty R. wrote:

Dan, I'm not sure I understand your question. Are you challenging the reader to do the puzzle without using that 28 pair in r7? Also, what is a naked single? To me it sounds like a solved cell?

Quote:

In my book, "hard". Can be solved by hidden singles only, no sets.

I could not see how to proceed without using a set (the pair) I thought I was missing something.

A naked single is the case when there is only one candidate left for a cell. The cell can "see" the other eight candidates. When doing a puzzle by pencil it is difficult to find these critters. It is easy when a solver computes the candidates for each cell automatically. Here the cell with only one candidate is the naked single. I believe that both hidden and naked pairs, triples, quads, and quints are sets. A set is more than one so a hidden single is not a set. Looking forward to learning more about this.

keith

Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

Posted: Thu Oct 27, 2011 9:36 pm Post subject: Re: "Meister Sudokus" puzzle 40

arkietech wrote:

keith wrote:

In my book, "hard". Can be solved by hidden singles only, no sets.

How do you handle this with no sets?

Code:

A great puzzle! to me some naked singles are very hard.

Here is the sticking point I reached:

Code:

+-------------------+-------------------+-------------------+
| 2789 6 2789 | 379 3579 4 | 358 1 3589 |
| 1789 189 4 | 379 2 1359 | 358 6 3589 |
| 3 19 5 | 8 6 19 | 2 4 7 |
+-------------------+-------------------+-------------------+
| 6 5 238 | 23 34 7 | 1 9 48 |
| 189 4 1389 | 6 359 3589 | 7 2 58 |
| 289 7 289 | 1 459 2589 | 458 3 6 |
+-------------------+-------------------+-------------------+
| 4 238 2378 | 237 37 6 | 9 5 1 |
| 5 1239 12369 | 4 8 239 | 36 7 23 |
| 279 239 23679 | 5 1 239 | 346 8 234 |
+-------------------+-------------------+-------------------+

You don't need any pairs to do this, nor pencil marks:
The 7 in B8 is in R7.
Look at B1. 23 in C2 must be in B7.
Thus, R7C3 is 8. Puzzle solved.

Honest, Charlie, that's how I solved it.

(But, as I said, I was forewarned it could be solved with singles only.)

Keith

arkietech

Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

Posted: Thu Oct 27, 2011 10:22 pm Post subject: Re: "Meister Sudokus" puzzle 40

keith wrote:

Look at B1. 23 in C2 must be in B7.
Thus, R7C3 is 8. Puzzle solved.

I call that a pair and a set(23).

keith

Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

Posted: Thu Oct 27, 2011 10:30 pm Post subject: Re: "Meister Sudokus" puzzle 40

arkietech wrote:

keith wrote:

Look at B1. 23 in C2 must be in B7.
Thus, R7C3 is 8. Puzzle solved.

I call that a pair and a set(23).

A pair is two candidates (in this case 23) that must lie in three cells (C2B7)?

News to me. I thought a set was n candidates in n cells.

I will concede "intersection", but not "set".

Keith

daj95376

Joined: 23 Aug 2008
Posts: 3854

Posted: Thu Oct 27, 2011 10:35 pm Post subject: Re: "Meister Sudokus" puzzle 40

keith wrote:

Here is the sticking point I reached:

Code:

According to HoDoKu 2.1.1, there aren't any singles present in this grid -- naked or hidden. However, there is a Locked Candidate Type 2 for <2> in c2b7. After this, naked and hidden singles complete the puzzle.

Singles are considered different than Sets, but I don't recall why they're different. Sudopedia.org has all of the details if you're curious.

I also consider Singles as different from Sets because my solver's logic handles them differently.

Regards, Danny

daj95376

Joined: 23 Aug 2008
Posts: 3854

Posted: Thu Oct 27, 2011 10:55 pm Post subject:

An "easy" puzzle and initial grid from Simple Sudoku.

Code:

*-----------*
|...|21.|87.|
|...|...|...|
|4.1|.8.|53.|
|---+---+---|
|..5|6..|3.7|
|...|5.2|...|
|9.7|..3|1..|
|---+---+---|
|.14|.2.|6.8|
|...|...|...|
|.82|.67|...|
*-----------*

*-----------------------------------------------------------------------------*
| 356 3569 369 | 2 1 4569 | 8 7 469 |
| 235678 235679 3689 | 3479 34579 4569 | 249 12469 12469 |
| 4 2679 1 | 79 8 69 | 5 3 269 |
|-------------------------+-------------------------+-------------------------|
| 128 24 5 | 6 49 1489 | 3 2489 7 |
| 1368 346 368 | 5 479 2 | 49 4689 469 |
| 9 246 7 | 48 4 3 | 1 24568 2456 |
|-------------------------+-------------------------+-------------------------|
| 357 1 4 | 39 2 59 | 6 59 8 |
| 3567 35679 369 | 13489 3459 14589 | 2479 12459 123459 |
| 35 8 2 | 1349 6 7 | 49 1459 13459 |
*-----------------------------------------------------------------------------*

There is a Naked Single, r6c5=4. It is not a "solved cell" because there are <4> candidates still present in [b5], [c4], and [r6]. By comparison, the only <7> candidate in [b5] (or [r5]) is in r5c5, so it's a Hidden Single.

Ironically, if you take the grid and paste it into Simple Sudoku, then SS will erroneously treat r6c5=4 as a given and eliminate the <4> candidates in the other cells of [b5], [c5], [r6].

Code:

*-----------*
|...|21.|87.|
|...|...|...|
|4.1|.8.|53.|
|---+---+---|
|..5|6..|3.7|
|...|5.2|...|
|9.7|.43|1..|
|---+---+---|
|.14|.2.|6.8|
|...|...|...|
|.82|.67|...|
*-----------*

*-----------------------------------------------------------------------------*
| 356 3569 369 | 2 1 4569 | 8 7 469 |
| 235678 235679 3689 | 3479 3579 4569 | 249 12469 12469 |
| 4 2679 1 | 79 8 69 | 5 3 269 |
|-------------------------+-------------------------+-------------------------|
| 128 24 5 | 6 9 189 | 3 2489 7 |
| 1368 346 368 | 5 79 2 | 49 4689 469 |
| 9 26 7 | 8 4 3 | 1 2568 256 |
|-------------------------+-------------------------+-------------------------|
| 357 1 4 | 39 2 59 | 6 59 8 |
| 3567 35679 369 | 13489 359 14589 | 2479 12459 123459 |
| 35 8 2 | 1349 6 7 | 49 1459 13459 |
*-----------------------------------------------------------------------------*

Regards, Danny

Display posts from previous:

	dailysudoku.com Forum Index -> Other puzzles	All times are GMT Goto page Previous 1, 2, 3 Next
Page 2 of 3

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum