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sheryl
Joined: 24 Sep 2007
Posts: 64
Location: New York
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 Posted: Wed Apr 09, 2008 1:16 pm Post subject: Super Tough |
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Would anyone like to try this (after basics) from the Krazydad site.
| Code: |
+------------+------------------+---------------+
| 89 5 19 | 1678 78 2 | 468 147 3 |
| 18 3 6 | 4 178 9 | 2 5 78 |
| 4 2 7 | 1368 5 1368 | 68 19 689 |
+------------+------------------+---------------+
| 3 1 25 | 2678 4 5678 | 568 79 6789 |
| 256 78 245 | 12678 9 15678 | 3 47 678 |
| 569 78 459 | 678 3 5678 | 4567 2 1 |
+------------+------------------+---------------+
| 25 9 235 | 378 278 378 | 1 6 4 |
| 12 6 8 | 9 12 4 | 7 3 5 |
| 7 4 13 | 5 6 13 | 9 8 2 |
+------------+------------------+---------------+
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I could not solve it, so any info would be appreciated. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Wed Apr 09, 2008 4:39 pm Post subject: |
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There is a short xy-chain (a.k.a. w-wing), that removes 7 from r1c8 r2c5
'78'(r1c5)...r1c1,r1c3,r2c1...'78'(r2c9)
and solves r2c9=7.
| Code: |
+--------------------------+--------------------------+--------------------------+
| 89 5 19 | 1678 78 2 | 468 14 3 |
| 18 3 6 | 4 18 9 | 2 5 7 |
| 4 2 7 | 1368 5 1368 | 68 19 689 |
+--------------------------+--------------------------+--------------------------+
| 3 1 25 | 2678 4 5678 | 568 79 689 |
| 256 78 245 | 12678 9 15678 | 3 47 68 |
| 569 78 459 | 678 3 5678 | 4568 2 1 |
+--------------------------+--------------------------+--------------------------+
| 25 9 235 | 378 278 378 | 1 6 4 |
| 12 6 8 | 9 12 4 | 7 3 5 |
| 7 4 13 | 5 6 13 | 9 8 2 |
+--------------------------+--------------------------+--------------------------+
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so much for the first round, I'll continue later ...
BTW, starting from the solved cells, I could not reach the position without an x-wing (1). |
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sheryl
Joined: 24 Sep 2007
Posts: 64
Location: New York
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| Posted: Wed Apr 09, 2008 5:02 pm Post subject: |
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| i might have had an x-wing. i've been working on this puzzle for several days so i'm not sure how i got to the point i'm at, i just know i can't go any further, so i might have mis spoke when i said AFTER BASICS. |
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sheryl
Joined: 24 Sep 2007
Posts: 64
Location: New York
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| Posted: Wed Apr 09, 2008 5:08 pm Post subject: |
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| nataraj wrote: | There is a short xy-chain (a.k.a. w-wing), that removes 7 from r1c8 r2c5
'78'(r1c5)...r1c1,r1c3,r2c1...'78'(r2c9)
and solves r2c9=7.
| Code: |
+--------------------------+--------------------------+----------------------
| 89 5 19 | 1678 78 2 | 468 14 3 |
| 18 3 6 | 4 18 9 | 2 5 7 |
| 4 2 7 | 1368 5 1368 | 68 19 689 |
+--------------------------+--------------------------+-----------------------
| 3 1 25 | 2678 4 5678 | 568 79 689 |
| 256 78 245 | 12678 9 15678 | 3 47 68 |
| 569 78 459 | 678 3 5678 | 4568 2 1 |
+--------------------------+--------------------------+-----------------------
| 25 9 235 | 378 278 378 | 1 6 4 |
| 12 6 8 | 9 12 4 | 7 3 5 |
| 7 4 13 | 5 6 13 | 9 8 2 |
+--------------------------+--------------------------+--------------------------+
|
so much for the first round, I'll continue later ...
BTW, starting from the solved cells, I could not reach the position without an x-wing (1). |
for some reason your puzzle is too long for me???? can you give me the actual xy chain with cell addresses. i can't follow yours (unless i'm reading it wrong.) |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Wed Apr 09, 2008 6:15 pm Post subject: |
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| sheryl wrote: | | can you give me the actual xy chain with cell addresses. i can't follow yours (unless i'm reading it wrong.) |
The chain is '78'(r1c5)...r1c1,r1c3,r2c1...'78'(r2c9) ,
which means it starts at cell r1c5 (value {7,8}) through r1c1 .... and ends at r2c9 (value {7,8}).
This just my shorthand, no wonder you couldn't read it 
The grid in my post shows the position after applying the xy-chain and solving cell r2c9.
I've done some more exploring, but other than extended medusa (start at cell r1c3 or any cell of that huge web of strongly connected 1s. Reach a contradiction - if r1c3=1 then r4c3 can be neither 2 nor 5) I did not see any smart moves. I'd consider this puzzle way beyond "vh". |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Wed Apr 09, 2008 7:44 pm Post subject: |
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I don't know anything about Krazydad sudokus - are they supposed to be solvable without guessing? I don't believe this one can be.
Sheryl: I hate to ask - but are you sure you copied down all the given candidates?
As for the power of guessing - if you go to the first pair in the first cell R1C1 and assume its is the first number - ie <8> - the puzzle suddenly becomes a Very Easy. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Wed Apr 09, 2008 9:53 pm Post subject: |
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| cgordon wrote: | | As for the power of guessing - if you go to the first pair in the first cell R1C1 and assume its is the first number - ie <8> - the puzzle suddenly becomes a Very Easy. |
Same in lotto.
If you happen to write down the correct numbers, life suddenly becomes very easy  |
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sheryl
Joined: 24 Sep 2007
Posts: 64
Location: New York
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| Posted: Wed Apr 09, 2008 10:01 pm Post subject: |
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| go to krazydad.com, it's the supr tough puzzles book 1, puzzle 6 and you can see for yourself - i didn't actually write the numbers anyway, i printed it out with the numbers. |
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sheryl
Joined: 24 Sep 2007
Posts: 64
Location: New York
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| Posted: Wed Apr 09, 2008 10:12 pm Post subject: |
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| nataraj wrote: |
I've done some more exploring, but other than extended medusa (start at cell r1c3 or any cell of that huge web of strongly connected 1s. Reach a contradiction - if r1c3=1 then r4c3 can be neither 2 nor 5) I did not see any smart moves. I'd consider this puzzle way beyond "vh". |
if r1c3 (1,9) = 1 then r4c3 (2,5) can not be a 2 or a 5. i don't get that reasoning, can you explain??? |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Wed Apr 09, 2008 10:39 pm Post subject: |
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| sheryl wrote: |
if r1c3 (1,9) = 1 then r4c3 (2,5) can not be a 2 or a 5. i don't get that reasoning, can you explain??? |
The reasoning is this:
assume r1c3=1.
r1c3=1 => r2c1=8 => r2c5=1 => ("neither") r13c3<>1 => r5c4=1 => r4c4=2
r1c3=1 => r6c3=9 => r6c7=4 => r4c7=5
Row 4 has 2 and 5 in locations other than r4c3. This cannot be, thus our assumption must have been wrong.
How did I find it? Lucky guess. Lotto. Well, not exactly. I looked at the "dot grids" and found that "1" had seven cells strongly connected.
| Code: |
+·····+·····+·····+
· #·o · # ·
· /-/|· · | ·
·#-------# · | ·
·| |· | · | ·
·| |·o | o· # ·
+|···|+··|··+·····+
·| |· | · ·
·| |· | · ·
·| |·*---*· ·
·| |· | · ·
·| |· | · ·
+|···|+··|··+·····+
·| |· | · ·
·| |· | · ·
·#-------# · ·
· \-\|· \ · ·
· #-----#· ·
+·····+·····+·····+
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Any one of those 7 cells would be a good starting point for medusa coloring. Medusa alone does not solve the puzzle, though. One needs "extended".
I still hope that someone here comes up with a better solution.
________
And once more: NO "very hard" tomorrow
:((( |
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Victor
Joined: 29 Sep 2005
Posts: 207
Location: NI
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| Posted: Wed Apr 09, 2008 10:50 pm Post subject: |
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As Nataraj says, beyond VH - way beyond indeed. Here are a couple more moves, not actually solving any cells.
| Code: |
+--------------+-----------------+--------------+
| 89 5 19D | 1678 78 2 | 468 14A 3 |
| 18 3 6 | 4 18 9 | 2 5 7 |
| 4 2 7 | 1368 5 1368 | 68 19 689 |
+--------------+-----------------+--------------+
| 3 1 25# | 2678 4 5678 | 568 79 689 |
| 256* 78* 245*| 12678 9 15678 | 3 47* 68* |
| 569 78 459C| 678 3 5678 | 4568B 2 1 |
+--------------+-----------------+--------------+
| 25 9 235 | 378 278 378 | 1 6 4 |
| 12 6 8 | 9 12 4 | 7 3 5 |
| 7 4 13 | 5 6 13 | 9 8 2 |
+--------------+-----------------+--------------+
|
1. I like the technique "ALS" when one of the sets is a single cell. I'll explain it in case you haven't met it. (Don't think it's popular in this forum.) The *'d cells form an 'almost locked set' - one number too many. Now try each of the numbers in #. If # is 2, then the *s become a locked set: you could eliminate the 5 from r5c6 (which doesn't matter here), and also the other two 5s in box 4 - in C & the cell two to the left. Alternatively if # is 5, well then, again you can eliminate those two 5s: so they can go.
2. I like to look for AICs in my head - not often with success, but I found one here. (Remember that the 5 has gone from C.) Suppose A is not 1 (i.e. is 4). Then B is 4, and C is 9 and D is 1. This is reversible, like all AICs: if you start with D <> 1 you end up with A = 1. So that kills the remaining 1 in r1 (i.e. in r1c4).
3. Sorry, can't see anything more. Over to somebody else. |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Wed Apr 09, 2008 11:09 pm Post subject: |
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Victor,
I, for one, like ALS eliminations. However, in this case, your ALS is a bit more powerful than you realize because it is also a Sue De Coq:
| Code: | +--------------------+----------------------+---------------+
| 89 5 19 | 1678 78 2 | 468 14 3 |
| 18 3 6 | 4 18 9 | 2 5 7 |
| 4 2 7 | 1368 5 1368 | 68 19 689 |
+--------------------+----------------------+---------------+
| 3 1 @25 | 2678 4 5678 | 568 79 689 |
|@256 @78 @245 |#12[678] 9 #15[678] | 3 @47 @68 |
|#[5]69 78 #4[5]9 | 678 3 5678 | 4568 2 1 |
+--------------------+----------------------+---------------+
| 25 9 235 | 378 278 378 | 1 6 4 |
| 12 6 8 | 9 12 4 | 7 3 5 |
| 7 4 13 | 5 6 13 | 9 8 2 |
+--------------------+----------------------+---------------+ |
The 6 Sue De Coq cells, marked @, contain exactly 6 digits and overlap in R5c123. The non-overlapping remote sets (r4c3 and r5c89) do not share any common digits. So, <2> and <5> can be eliminated in any other b4 cells (the two <5> eliminations you've already noted), and, <4>, <6>, <7> and <8> can be eliminated from any other cells in r5. Here, {678} are eliminated from both of r5c46.
This doesn't get us very far, but removes a bit of clutter.
After this, I don't believe there are any solutions other than AICs. nataraj's extended Medusa will solve it, as will (less controversially) Medusa multi-coloring.
natarj,
Your "lotto" forcing can be expressed as a roundabout AIC:
(1-9)r1c3=(9-4)r6c3=(4-5)r6c7=(5)r4c7-(5=2)r4c3-(2)r4c4=
(2-1)r5c4=(1)r13c4-(1=8)r2c5-(8=1)r2c1-(1)r1c3; r1c3<>1 |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Wed Apr 09, 2008 11:55 pm Post subject: |
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Medusa multi-coloring after the Sud De Coq eliminations turns out to be quite simple. First, an Aa cluster starting with those <1>s:
| Code: | +----------------+------------------+-----------------+
| 8a9A 5 1A9a |#-1678 78 2 | 4a68 1a4A 3 |
| 1a8A 3 6 | 4 1A8a 9 | 2 5 7 |
| 4 2 7 | 1368 5 1368 | 68 1A9a 689A |
+----------------+------------------+-----------------+
| 3 1 25 | 2678 4 5678 | 568 7a9A 689a |
| 256a 7a8A 24A5 | 12 9 15 | 3 4a7A 6A8a |
| 6A9a 7A8a 4a9A | 678 3 5678 | 4A568 2 1 |
+----------------+------------------+-----------------+
| 25 9 23a5 | 378 2a78 378 | 1 6 4 |
| 1A2a 6 8 | 9 1a2A 4 | 7 3 5 |
| 7 4 1a3A | 5 6 1A3a | 9 8 2 |
+----------------+------------------+-----------------+ |
Victor's <1> elimination in r1c4 is found easily.
Next, I add a Bb cluster using the remaining <1>s. There is an Ab "bridge" in c6, which means that aB is the resulting strong pair:
| Code: | +------------------+------------------+------------------+
| 8a9A 5 1A9a | 678 78 2 | 4a68 1a4A 3 |
| 1a8A 3 6 | 4 1A8a 9 | 2 5 7 |
| 4 2 7 | 1b368 5 1B368 | 68 #-1A9a 689A |
+------------------+------------------+------------------+
| 3 1 2b5B | 2B678 4 5678 | 568 7a9A 689a |
|#2-56a 7a8A 24A5 | 1B2b 9 1b5B | 3 4a7A 6A8a |
| 6A9a 7A8a 4a9A | 678 3 5678 | 4A568 2 1 |
+------------------+------------------+------------------+
| 25 9 #23a-5 | 378 2a78 378 | 1 6 4 |
| 1A2a 6 8 | 9 1a2A 4 | 7 3 5 |
| 7 4 1a3A | 5 6 1A3a | 9 8 2 |
+------------------+------------------+------------------+
Strong pair: aB |
<5>s are trapped in b4 and b7, as marked. But much more importantly, a <1A> is trapped in r3c8 (by 1B in r3c6 and 9a in r3c8). This means that all "A" values are false and all "a" values true and the puzzle is solved. |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Thu Apr 10, 2008 11:22 am Post subject: |
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After w-wing:
| Code: | *----------------------------------------------------*
| 89 5 19 | 1678 78 2 | 468 14 3 |
| 18 3 6 | 4 18 9 | 2 5 7 |
| 4 2 7 | 1368 5 1368 | 68 19 689 |
|---------------+--------------------+---------------|
| 3 1 #25 |*2678 4 5678 | 568 79 689 |
| 256 78 245 |*12678 9 *15678 | 3 47 68 |
| 569 78 459 | 678 3 5678 | 456 2 1 |
|---------------+--------------------+---------------|
|#25 9 &235 | 378 278 378 | 1 6 4 |
|*12 6 8 | 9 *12 4 | 7 3 5 |
| 7 4 13 | 5 6 *13 | 9 8 2 |
*----------------------------------------------------* |
Looking at a connection between pairs 25 turned out to pin 5 to r7c1:
r4c3=5 => r7c1=5
r4c3=2 => r5c4=2 => r5c6=1 => r8c5=1 => r8c1=2 => r7c1=5 | Code: |
--------------------------------------------------*
| 89 5 19 | 1678 78 2 | 468 14 3 |
| 18 3 6 | 4 18 9 | 2 5 7 |
| 4 2 7 | 1368 5 1368 | 68 19 689 |
|--------------+--------------------+---------------|
| 3 1 *25 | 2678 4 5678 |*568 79 689 |
|*26 78 245 | 12678 9 15678 | 3 47 68 |
|*69 78 #459 | 678 3 5678 |#456 2 1 |
|--------------+--------------------+---------------|
| 5 9 23 | 378 278 378 | 1 6 4 |
| 12 6 8 | 9 12 4 | 7 3 5 |
| 7 4 13 | 5 6 13 | 9 8 2 |
*---------------------------------------------------* |
Strong link for 4 in r6:
r6c3=4 or
r6c7=4 => r4c7=5 => r4c3=2 => r6c1=6 => r7c1=9 ==> r6c3<>9
[Edit: corrected, thought 5 would be eliminated also this way. I had this one first, but it did not help much:
Strong link for 4 in c3:
r6c3=4 or
r5c3=4 => r5c6=5 => r5c4=1 => r4c4=2 => r4c3=5 ==> r6c3<>5] |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Thu Apr 10, 2008 5:46 pm Post subject: |
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I am actually surprised the krazydad puzzles aren't discussed more on this site. if you do any search for tough puzzles you are sure to come across his site.
those "super tough" puzzles have a very wide range in difficulty. I fed some into SE and spit out anywhere from 6.6 to 8.4. wow.
for example...
here is a SE 7.1 from book 3 in his "super tough"
| Code: | 8..|.53|...
.1.|.9.|...
...|...|495
---+---+---
..8|.6.|2..
.3.|...|.1.
..4|.8.|7..
---+---+---
657|...|...
...|.2.|.3.
...|64.|..9 |
then this 8.4 from the same book
| Code: | 7..|2..|..9
...|.7.|2.6
..8|3..|...
---+---+---
3..|.9.|5..
.4.|...|.3.
..1|.6.|..7
---+---+---
...|..5|7..
4.3|.1.|...
5..|..8|..4 |
Clearly, his ratings become meaningless if you go into each group expecting a homogeneous level of difficulty. instead, his groupings have more to do with how long the puzzle will take you to complete if you just print it out and want to do it by hand, rather than the difficulty of the techniques required. |
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sheryl
Joined: 24 Sep 2007
Posts: 64
Location: New York
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| Posted: Sat Apr 12, 2008 11:47 am Post subject: |
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| Actually all the toughs mirror the "Hard" on this site. But you are right about the SuperToughs, they range in difficulty and I think can be much harder than these VHs. They certainly have a wide range of solving techniques that i've never heard of. But for me this wide variety makes it impossible to spend the same amount of time solving them, since i'm not that familiar with all these different techniques (like sue de coq!). |
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