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 Post subject: Assassin 187
PostPosted: Fri Jan 08, 2010 8:05 pm 
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Posts: 43
A belated Happy New Year to you all!

This is a rather easy puzzle, so it may leave some of you unsatisfied, especially since we've had so few lately. But every time I tried to increase the difficulty, it either became a tedious mess, or it messed up my "artwork". I decided to leave it alone.

I was trying to come up with a Christmas-themed puzzle, and I must say it's difficult to be artistic on the limited "canvas" provided by a 9x9 grid! The 25(4) and 22(4) cages starting in R2 are supposed to be "stars" (Yes I know the Magi followed a single star, but I needed symmetry also.) The 40(8) cage in R78 is a "manger", and the 21(3) & 17(3) starting in N8 are the "legs of the manger". Pretty corny, yes. :cheesey:

Haven't yet tried out Borge's coloring templates, so I hope he'll provide us with a better image, as he's done for so many puzzles lately. ;clapclap;

Enjoy!

Assassin 187

Image

3x3::k:3840:2049:2049:4099:4099:4099:5638:5638:2568:3840:2049:6411:8972:8972:8972:5647:5638:2568:3840:6411:8972:6411:4630:5647:8972:5647:2568:3611:8972:6411:1566:4630:4384:5647:8972:4387:3611:3611:1566:1566:4630:4384:4384:4387:4387:3885:3885:10287:10287:10287:10287:10287:4148:4148:3885:3639:1592:10287:10287:10287:2364:3901:4148:3639:3639:1592:5442:1347:4420:2364:3901:3901:3400:3400:5442:5442:1347:4420:4420:2383:2383:

Solution:
534781692
216594873
897263145
968152734
142376958
753948216
385617429
421839567
679425381

PS Score: 1.07


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PostPosted: Sat Jan 09, 2010 10:28 pm 
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Posts: 310
Location: MV, Germany
Thanks for this week's Assassin Ronnie!

Like you said it could be cracked quite easily though in my case I used a harder move than necessary but I only noticed after I've went through my walkthrough again. Oh well, you don't always have to take the easiest path. :cheesey:

A187 Walkthrough:

1. R789
a) Outies R9 = 20(3) = 9{38/47} since R8C5 <= 4 -> R8C46 = (789), 9 locked for R8+N8
b) 5 locked in R9C46 @ N8 for R9
c) 13(2) <> 8
d) Innies N7 = 12(2) <> 1,2,6
e) Innies N9 = 12(2) <> 1,2,6
f) 5(2) = [32/41]
g) 17(3): R9C6 <> 3 since 5,6 only possible there
h) 3 locked in R9C789 @ R9 for N9
i) Innies N9 = 12(2): R9C7 <> 9
j) 9 locked in R7C89 @ N9 for R7

2. R789
a) ! 14(3) <> 3 because {347} blocked by Killer pair (47) of 13(2) and {356} blocked
by Killer triple (345) of Innies N7 + 6(2)
b) Hidden Single: R7C1 = 3 @ N7, R8C5 = 3 @ R8 -> R9C5 = 2
c) Innie N7 = R9C3 = 9
d) 13(2) = {67} locked for R9+N7
e) 9(2) = {18} locked for R9+N9
f) Outies R9 = 17(2) = {89} -> R8C4 = 8, R8C6 = 9
g) Cage sum: R9C4 = 4
h) R9C6 = 5 -> R9C7 = 3
i) 40(8) = {12346789} -> 2,3,4,8,9 locked for R6; 1,6,7 locked for R7+40(8)
j) 15(3) @ N7 = {357} -> 5,7 locked for R6+N4
k) 16(3) = {169} -> R7C9 = 9; 1,6 locked for N6

3. R123
a) 1 locked in R23C7 @ C7 for N3
b) 10(3) = {235} locked for C9+N3
c) Innies N1 = 22(3) = 9{58/67} -> R3C2 = 9
d) 3 locked in 8(3) @ N1 = {134} locked for N1

4. C123
a) 9 locked in 14(3) @ C1 = 9{14/23}
b) Hidden Single: R7C2 = 8 @ N7
c) 8 locked in R46C3 @ N4 for C3
d) Innies N1 = 13(2) = {67} locked for C3+N1
e) Hidden Single: R4C2 = 6 @ N4
f) R3C3 = 7, R2C3 = 6
g) 25(4) = {2689} -> R3C4 = 2, R4C3 = 8
h) 6(3) = {123} -> R5C3 = 2; 1,3 locked for C4+N5

5. N67
a) 17(3) @ R4C9 = {458} since R45C9 = (478) -> R4C9 = 4, R5C9 = 8, R5C8 = 5
b) 17(3) @ C6 = 6{29/47} -> R5C6 = 6
c) 6(2) = {15} -> R7C3 = 5, R8C3 = 1
d) 17(3) @ C6 = {269} -> R4C6 = 2, R5C7 = 9
e) 35(7) = {1345679} -> R4C8 = 3

6. Rest is singles.

Rating:
Easy 1.25. I used a Killer triple.


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 Post subject: Re: Assassin 187
PostPosted: Sat Jan 09, 2010 11:36 pm 
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Joined: Mon Apr 21, 2008 10:32 am
Posts: 868
Ronnie G wrote:
I was trying to come up with a Christmas-themed puzzle, and I must say it's difficult to be artistic on the limited "canvas" provided by a 9x9 grid!
Haven't yet tried out Borge's coloring templates, so I hope he'll provide us with a better image, as he's done for so many puzzles lately.
Trying to be true to the Christmas theme, here my images with udosuk Style Killer Cages:
Image     Image

Using the killer generation process described in my post The easy/lazy way to make a killer sudoku I fairly easy generated several presumably harder versions of this puzzle.
Just pasted the v1 PS code into JSudoku and hit CTRL+SHIFT+R until SudokuSolver had some high SS Scores and used "interesting" techniques.

Below three of the puzzles. Have your pick.

When scoring all three puzzles SudokuSolver did NOT use chains or T&E for any of the three puzzles, but among others various versions of Ed's "interesting" solving techniques mentioned HERE.


Assassin 187 v2
SS Score: 1.75:
Image     Image
3x3::k:5120:3841:3841:2563:2563:2563:2566:2566:4360:5120:3841:3595:9740:9740:9740:7695:2566:4360:5120:3595:9740:3595:2838:7695:9740:7695:4360:2843:9740:3595:5150:2838:2592:7695:9740:4899:2843:2843:5150:5150:2838:2592:2592:4899:4899:3117:3117:10543:10543:10543:10543:10543:2868:2868:3117:3383:2360:10543:10543:10543:3388:3645:2868:3383:3383:2360:3138:3907:4420:3388:3645:3645:3656:3656:3138:3138:3907:4420:4420:2383:2383:

Solution:
954217368
862539714
317648295
185723649
739456182
426981573
648372951
271895436
593164827


Assassin 187 v3
SS Score: 2.33:
Image     Image
3x3::k:4864:1537:1537:3331:3331:3331:3846:3846:3592:4864:1537:6667:9228:9228:9228:6159:3846:3592:4864:6667:9228:6667:2070:6159:9228:6159:3592:3867:9228:6667:3358:2070:5664:6159:9228:3619:3867:3867:3358:3358:2070:5664:5664:3619:3619:4397:4397:9519:9519:9519:9519:9519:4148:4148:4397:4663:2360:9519:9519:9519:1596:4669:4148:4663:4663:2360:5698:2883:2116:1596:4669:4669:1608:1608:5698:5698:2883:2116:2116:3151:3151:

Solution:
832175649
716943852
495826713
123458967
687219534
954367128
371592486
568734291
249681375


Assassin 187 v4
SS Score: 3.08:
Image     Image
3x3::k:4608:1537:1537:3843:3843:3843:4614:4614:2568:4608:1537:5387:8204:8204:8204:4367:4614:2568:4608:5387:8204:5387:5142:4367:8204:4367:2568:4891:8204:5387:3614:5142:3616:4367:8204:5411:4891:4891:3614:3614:5142:3616:3616:5411:5411:3373:3373:10543:10543:10543:10543:10543:4404:4404:3373:4151:1848:10543:10543:10543:1340:3901:4404:4151:4151:1848:4674:1603:5444:1340:3901:3901:2632:2632:4674:4674:1603:5444:5444:2895:2895:

Solution:
621438957
539276841
748591362
953764218
286153794
417982635
862315479
375849126
194627583

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 Post subject: Re: Assassin 187
PostPosted: Wed Jan 13, 2010 11:32 pm 
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Joined: Wed Apr 23, 2008 6:04 pm
Posts: 1895
Location: Lethbridge, Alberta, Canada
Ronnie has encouraged me to post my coloured cage pattern for this Christmas-themed puzzle so here it is.

Image

I've mentioned previously in the forum that I use an Excel worksheet for solving sudokus. Here is my diagram for A187 after doing the Prelims. I normally use red for cage totals, green for candidates which I replace with blue when a cell is fixed; I've changed to black for this diagram because it gave a clearer image. I add notes, the result of applying 45s etc. in white cells below the diagram.

I've also posted another diagram in The Messier, The Merrier thread which has extra information that I used to keep track of the disjoint cages in that extremely messy cage pattern.

Image

Rating Comment:
I'll rate my walkthrough for A187 at Easy 1.25. I used a blocking triple and a hidden killer triple.

Afmob's triple was a neat and very useful step. It was probably harder than either of my triples since it was applied to a combined cage formed from a 2-cell cage and a hidden cage.


Here is my walkthrough for A187. It's fairly long because I didn't spot Afmob's step 1b. :oops:

Prelims

a) R78C3 = {15/24}
b) R78C7 = {18/27/36/45}, no 9
c) R89C5 = {14/23}
d) R9C12 = {49/58/67}, no 1,2,3
e) R9C89 = {18/27/36/45}, no 9
f) 8(3) cage in N1 = {125/134}
g) 22(3) cage in N3 = {589/679}
h) 10(3) cage at R1C9 = {127/136/145/235}, no 8,9
i) 6(3) cage at R4C4 = {123}
j) 21(3) cage at R8C4 = {489/579/678}, no 1,2,3
k) 40(8) cage at R6C3 = {12346789}, no 5

Steps resulting from Prelims
1a. 8(3) cage in N1 = {125/134}, 1 locked for N1
1b. 22(3) cage in N3 = {589/679}, 9 locked for N3
1c. 6(3) cage at R4C4 = {123}, CPE no 1,2,3 in R5C56

2. 45 rule on N7 2 innies R7C1 + R9C3 = 12 = [39]/{48/57}, no 1,2,6, no 9 in R7C1

3. 45 rule on N9 2 innies R7C9 + R9C7 = 12 = {39/48/57}, no 1,2,6

4. 45 rule on N1 3 innies R2C3 + R3C23 = 22 = {589/679}, 9 locked for N1, CPE no 9 in R3C4 + R4C3

5. 45 rule on N3 3 innies R2C7 + R3C78 = 13 = {148/238/247/346} (cannot be {157/256} which clash with 22(3) cage), no 5

6. 45 rule on R9 3 outies R8C456 = 20 = {389/479} (cannot be {569/578} because R8C5 only contains 1,2,3,4), no 1,2,5,6, 9 locked for R8 and N8, clean-up: no 3,4 in R9C5
6a. R8C5 = {34} -> no 3,4 in R8C46
[Here I missed 5 in N8 only in R9C46, locked for R9.]

7. 9 in 40(8) cage only in R6C34567, locked for R6

8. 45 rule on C12 2 innies R34C2 = 1 outie R1C3 + 11
8a. Min R34C2 = 12, no 1,2

9. Hidden killer pair 1,2 in 14(3) cage and R78C3 for N7, R78C3 has one of 1,2 -> 14(3) cage must have one of 1,2
9a. 14(3) cage = {158/167/239/248} (cannot be {149/257} which clash with R78C3, cannot be {347/356} which don’t contain one of 1,2)
9b. Hidden killer pair 6,7 in 14(3) cage and R9C12 for N7 (because 6 in N7 only in these cages) -> either 14(3) cage or R9C12 must contain both of 6,7
[Maybe this step is better called locking cages.]
9c. Killer pair 6,7 in 14(3) cage and R9C12, locked for N7, clean-up: no 5 in R7C1 + R9C3 (step 2)

10. 15(3) cage at R1C1 = {258/267} (cannot be {357/456} which clash with 8(3) cage, cannot be {348} which clashes with R7C1), no 3,4, 2 locked for C1 and N1, clean-up: no 5 in 8(3) cage in N1

11. 14(3) cage in N7 (step 9a) = {158/167/239/248}
11a. 3 of {239} must be in R8C1 -> no 3 in R78C2
11b. 3 in N7 only in R78C1, locked for C1

12. 21(3) cage at R8C4 = {489/579/678}
12a. 5,6 of {579/678} must be in R9C4 -> no 7 in R9C4

13. 17(3) cage at R8C6 = {179/278/359/368/458/467} (cannot be {269} because 2,6 only in R9C6)
13a. 1,2 of {179/278} must be in R9C6, 7,8 of {368/458/467} must be in R8C6 -> no 7,8 in R9C6

14. Hidden killer triple 1,2,3 in R9C5, 17(3) cage at R8C6 and R9C89 for R9, R9C5 contains one of 1,2, 17(3) cage at R8C6 and R9C89 cannot contain more than one of 1,2,3 -> 17(3) cage at R8C6 must contain one of 1,2,3 in R9C67 and R9C89 must contain one of 1,2,3
14a. 17(3) cage at R8C6 (step 13) = {179/278/359/368} (cannot be {458/467} which don’t contain any of 1,2,3), no 4, clean-up: no 8 in R7C9 (step 3)
14b. R9C89 = {18/27/36} (cannot be {45} which doesn’t contain any of 1,2,3), no 4,5

15. R9C12 = {58/67} (cannot be {49} which clashes with R7C1 + R9C3), no 4,9
[I ought to have spotted that after step 9c although it only becomes powerful after steps 14a and 14b.]

16. 4 in R9 only in R9C34 -> 21(3) cage at R8C4 = {489} (only remaining combination)

17. 9 in R89 only in R8C46 and R9C37 -> 21(3) cage at R8C4 and 17(3) cage at R8C6 must both contain 9 -> 17(3) cage (step 14a) = {179/359} (cannot be {278/368} which don’t contain 9), no 2,6,8, clean-up: no 4 in R7C9 (step 3)

18. 6 in N8 only in R7C456, locked for R7 and 40(8) cage at R6C3, no 6 in R6C34567, clean-up: no 3 in R8C7
[Even after that I still missed that R9C6 is hidden single 5 for N8.]

19. 6 in C3 only in R234C3, CPE no 6 in R3C24

20. 9 in C1 only in R45C1, locked for N4
20a. 14(3) cage in N4 = {149} (only remaining combination containing 9, cannot be {239} because 2,3 only in R5C2), locked for N4

21. 1 in 6(3) cage at R4C4 only in R45C4, locked for C4 and N5

22. Hidden killer pair 1,4 in R45C1 and R78C1 for C1, R45C1 must contain one of 1,4 -> R78C1 must contain one of 1,4
22a. Killer pair 1,4 in R78C1 and R78C3, locked for N7, clean-up: no 8 in R7C1 (step 2)
22b. Naked quint {25678} in R12369C1, locked for C1

23. 15(3) cage at R6C1 = {348/357/456} (cannot be {258/267} because R7C1 only contains 3,4), no 2
23a. 8 of {348} must be in R6C1 -> no 8 in R6C2

24. 2 in N4 only in R456C3, locked for C3, clean-up: no 4 in R78C3

25. Naked pair {15} in R78C3, locked for C3 and N7, clean-up: no 8 in R9C12

26. Naked pair {67} in R9C12, locked for R9 and N7, clean-up: no 5 in R7C9 (step 3), no 2,3 in R9C89

27. Naked pair {18} in R9C89, locked for R9 and N9 -> R9C34 = [94], R8C4 = 8, R89C5 = [32], R78C1 = [34], R78C2 = [82], R9C67 = [53], R8C6 = 9 (step 13), R7C9 = 9 (step 3), clean-up: no 5,7 in R7C7, no 6 in R8C7

28. Naked triple {167} in R7C456, locked for R7 and 40(8) cage at R6C3, no 1,7 in R6C34567 -> R78C3 = [51]

29. Naked quint {23489} in R6C34567, locked for R6

30. 15(3) cage at R6C1 (step 23) = {357} (only remaining combination), 5,7 locked in R6C12, locked for R6 and N4

31. Naked pair {16} in R6C89, locked for N6

32. 1 in C7 only in R23C7, locked for N3

33. 10(3) cage at R1C9 = {235} (only remaining combination), locked for C9 and N3

34. 22(3) cage in N3 = {679} (only remaining combination), locked for N3

35. 4 in C9 only in R45C9, locked for N6
35a. 17(3) cage in N6 = {458} (only remaining combination containing 4) -> R5C8 = 5, R45C9 = {48}, locked for C9 and N6 -> R9C89 = [81], R6C89 = [16], R8C89 = [67], R3C8 = 4, R7C8 = 2, R78C7 = [45]

36. Naked pair {79} in R12C8, locked for C8 and N3 -> R1C7 = 6, R4C8 = 3, R4C2 = 6, R9C12 = [67], R6C12 = [75], R3C2 = 9

37. Naked triple {238} in R456C3, locked for C3 -> R1C3 = 4, R23C3 = [67]

38. R5C2 = 4 (hidden single in C2), R45C9 = [48]

39. R2C3 + R3C2 = [69] = 15 -> R3C4 + R4C3 = 10 -> R4C3 = 8, R3C4 = 2, R45C4 = [13], R5C3 = 2, R6C4 = 9, R2C4 = 5

40. 35(7) cage at R2C4 = {1345679} (only combination without 2), no 8

and the rest is naked singles.


Last edited by Andrew on Sun Feb 14, 2010 5:51 am, edited 1 time in total.

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 Post subject: Re: Assassin 187
PostPosted: Thu Jan 14, 2010 7:06 pm 
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Grand Master
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Joined: Wed Apr 16, 2008 1:16 am
Posts: 1044
Location: Sydney, Australia
Ronnie G wrote:
This is a rather easy puzzle...
It felt that way to me ....but it is a satisfying key move. Not so easy to find (Afmob missed it!!) but available right near the beginning (step 5). So thanks very much Ronnie!

Yet again I have to express my amazement at the way Andrew solves! Thanks for showing us the lovely pics Andrew.

Assassin 187 beginning
7 steps:
Prelims
i. 8(3)n1: no 6,7,8,9
ii. 22(3)n3: no 1,2,3,4
iii. 10(3)n3: no 8,9
iv. 6(3)n5 = {123}
v. 40(8)n4: no 5
vi. 6(2)n7 = {15/24}
viii. 9(2)r7c7 & r9c8: no 9
ix. 21(3)n8: no 1,2,3
x. 5(2)n8 = {14/23}
xi. 13(2)n7: no 1,2,3

1. "45" on r9: 3 outies r8c456 = 20 (no 1,2)
1a. must have 3 or 4 in r8c5 = {389/479}
1b. 9 locked for r8 and n8
1c. r8c46 = (789)
1d. r9c5 = (12)

2. 5 in n8 only in r9: locked for r9
2a. no 8 in 13(2)n7
2b. no 4 in 9(2)n9

3. "45" on n7: 2 innies r7c1 + r9c3 = 12 (no 1,2,6)
3a. no 7,9 in r7c1

4. Hidden killer pair 1,2 in n7 in 6(2) and 14(3)
4a. ->14(3)n7 = {158/167/239/248} ({149/257} blocked by 6(2)n7)

5. 3 in n7 only in h12(2) = {39} or in 14(3) = {239}
5a. -> 9 locked for n7 (Locking Cages)

6. 13(2)n7 = {67}: both locked for r9 and n7
6a. no 5 in r7c1 (h12(2))

7. 9(2)n9 = {18}: both locked for r9 & n9
7a. no 4 in r7c1 (h12(2)n7)

on from here.
Cheers
Ed


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PostPosted: Thu Jan 14, 2010 7:58 pm 
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Joined: Mon Apr 21, 2008 9:44 am
Posts: 310
Location: MV, Germany
Three different ways to solve this Killer, great!

In my comment I said there was a technical easier move available to replace my Killer triple and both Ed and Andrew found the Hidden Killer pair (12) in N7 in 6(2) and 14(3) which lead to the rating SudokuSolver hinted at.


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 Post subject: Re: Assassin 187
PostPosted: Sun Jan 17, 2010 7:41 am 
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Joined: Wed Apr 23, 2008 6:04 pm
Posts: 1895
Location: Lethbridge, Alberta, Canada
Ed wrote:
Yet again I have to express my amazement at the way Andrew solves! Thanks for showing us the lovely pics Andrew.
It's good to know that my pics were appreciated. :D

I feel the same the opposite way round. I'm amazed that people can use software solvers in editor mode with the numbers in each cell in a 3x3 grid. Those numbers are too small for me. I sometimes have difficulty reading cage totals from posted puzzles when I'm setting up Excel worksheet diagrams for them.

Maybe the simple answer is that for lots of things, most people prefer the way they first do something unless they later find a much better way.

Apologies for the off-topic post.


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 Post subject: Re: Assassin 187
PostPosted: Fri Feb 18, 2011 3:13 am 
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Joined: Wed Apr 23, 2008 6:04 pm
Posts: 1895
Location: Lethbridge, Alberta, Canada
I only realised recently that I hadn't tried any of the A187 variants. Maybe there were too many puzzles at the time; nobody has posted any walkthroughs for them.

Thanks Børge for posting these variants using Ronnie's nice cage pattern.

It was a fun puzzle, not too difficult as variants go; a very pleasant change after some of the very hard variants that I've solved in recent months. For that reason I've given my walkthrough in hidden text, in the hope that others might want to try A187 V2.

If you want a hint:
Looks for CPEs as you work through this puzzle and the later variants. There's plenty of scope to use them in this cage pattern.

Rating Comment:
I'll rate my walkthrough for A187 V2 at 1.5. I used some hidden killer triples as blockers.

Here is my walkthrough for A187 V2:
Prelims

a) R78C3 = {18/27/36/45}, no 9
b) R78C7 = {49/58/67}, no 1,2,3
c) R89C5 = {69/78}
d) R9C12 = {59/68}
e) R9C89 = {18/27/36/45}, no 9
f) 20(3) cage in N1 = {389/479/569/578}, no 1,2
g) 10(3) cage in N2 = {127/136/145/236}, no 8,9
h) 10(3) cage in N3 = {127/136/145/235}, no 8,9
i) 11(3) cage at R3C5 = {128/137/146/236/245}, no 9
j) 11(3) cage in N4 = {128/137/146/236/245}, no 9
k) 20(3) cage at R4C4 = {389/479/569/578}, no 1,2
l) 10(3) cage at R4C6 = {127/136/145/235}, no 8,9
m) 19(3) cage in N6 = {289/379/469/478/568}, no 1
n) 11(3) cage at R6C8 = {128/137/146/236/245}, no 9
o) 14(4) cage at R2C3 = {1238/1247/1256/1346/2345}, no 9
p) 30(4) cage at R2C7 = {6789}
q) 41(8) cage at R6C3 = {12356789}, no 4
Also 38(7) cage at R2C4 = {1256789/1346789/2345789} must contain 7,8,9

1. Naked quad {6789} in 30(4) cage at R2C7, CPE no 6,7,8,9 in R3C7

2. 45 rule on R9 3 outies R8C456 = 22 = {589/679}, 9 locked for R8 and N8, clean-up: no 4 in R7C7, no 6 in R8C5
2a. R8C45 and R8C56 cannot total 15 (because they would clash with R89C5, CCC) -> no 7 in R8C46
2b. 9 in 41(8) cage at R6C3 only in R6C34567, locked for R6
2c. 4 in N8 only in R9C46, locked for R9, clean-up: no 5 in R9C89
2d. Min R8C4 = 5 -> max R9C34 = 7, no 7,8,9 in R9C34
[Ed pointed out that an alternative way to do step 2a is 45 rule on R9 2 outies R8C46 = 1 innie R9C5 + 7, IOU no 7 in R8C46. Thanks Ed! Step 2 is still needed to lock 9 for R8 and N8.]

3. Hidden killer triple 6,7,8 in R9C5, R9C89 and rest of R9 for R9, R9C5 = {678}, R9C89 contains one of 6,7,8 -> rest of R9 must contain one of 6,7,8
3a. R9C12 = {59} (cannot be {68} which contains two of 6,7,8), locked for R9 and N7, clean-up: no 4 in R78C3

4. 45 rule on N7 2 innies R7C1 + R9C3 = 9 = {36}/[72/81], no 1,2,4 in R7C1

5. 45 rule on N9 2 innies R7C9 + R9C7 = 9 = {18/27/36}, no 4,5

6. Hidden killer triple 6,7,8 in R7C9 + R9C7, R9C89 and rest of N9 for N9, R7C9 + R9C7 and R9C89 each contain one of 6,7,8 -> rest of N9 must contain one of 6,7,8
6a. R78C7 = {58}/[94] (cannot be {67} which contains two of 6,7,8), no 6,7

7. 9 in R7 only in R7C78
7a. 45 rule on R89 4 outies R7C2378 = 26 = {2789/3689/4589/4679}, no 1, clean-up: no 8 in R8C3

8. Hidden killer pair 4,9 in R78C7 and 14(3) cage for N9, either R78C7 must be [94] or 14(3) cage must contain both of 4,9 = 9{14} -> 4 must be in R8C789, locked for R8 and N9
8a. 14(3) cage = {149/158/257/356} (cannot be {167} which clashes with R9C89, cannot be {239/248/347} which only contain one of 4,9)

9. R7C2 = 4 (hidden single in R7), R8C12 = 9 = {18/27/36}
9a. R7C2378 (step 7a) = {4589/4679}, no 2,3, clean-up: no 6,7 in R8C3
9b. 5,9 of {4589} must be in R7C78 -> no 8 in R7C78, clean-up: no 5 in R8C7
9c. 5 of {4589} must be in R7C8 (because 14(3) cage in N9 = 9{14} clashes with R78C3 = [81]) -> no 5 in R7C7, clean-up: no 8 in R8C7

10. R78C7 = [94]
10a. 9 in 30(4) cage at R2C7 only in R3C68, locked for R3

11. 45 rule on N1 3 innies R2C3 + R3C23 = 10 = {127/136/145/235}, no 8

12. 17(3) cage at R8C6 = {179/269/278/368/458/467} (cannot be {359} because 5,9 only in R8C6) must contain one of 6,7,8 in R9C67
12a. Killer triple 6,7,8 in R9C5, R9C67 and R9C89, locked for R9, clean-up: no 3 in R7C1 (step 4)

13. R8C12 (step 9) = {18/27/36}, R8C456 (step 2) = {589/679} -> combined cage R8C12456 = {18}{679}/{27}{589}/{36}{589}, 8 locked for R8
13a. 14(3) cage in N9 (step 8a) = {257/356}, no 1
13b. 1 in R8 only in R8C123, locked for N7, clean-up: no 8 in R7C1 (step 4)

14. R7C2378 (step 9a) = {4589} (cannot be {4679} which clashes with R7C1) -> R7C8 = 5, R7C3 = 8, R8C3 = 1, clean-up: no 1 in R9C7 (step 5)
14a. 5,8 in 41(8) cage at R6C3 only in R6C34567, locked for R6

15. R8C456 = {589} (hidden triple in R8), locked for N8

16. 12(3) cage at R6C1 = {147/237/246}
16a. R7C1 = {67} -> no 6,7 in R6C12
16b. 4 of {147} must be in R6C1 -> no 1 in R6C1

17. 12(3) cage at R8C4 = {129/138/345}
17a. 1,4 only in R9C4 -> R9C4 = {14}

18. R89C5 = [87/96]
18a. 17(3) cage at R8C6 (step 12) = {269/278/458} (cannot be {179} = 9[17] or {368} = 8{36} which clash with R89C5, combo blocker, cannot be {467} because R8C6 only contains 5,8,9), no 1,3, clean-up: no 6 in R7C9 (step 5)
18b. 3 in N8 only in R7C456, locked for R7 and 41(8) cage at R6C3, no 3 in R6C34567, clean-up: no 6 in R9C7 (step 5)

19. 11(3) cage at R6C8 = {137/146/236}
19a. 2 of {236} must be in R7C9 -> no 2 in R6C89

20. 12(3) cage at R6C1 (step 16) = {147/237/246} -> R6C12 = {14/23/24}
20a. 11(3) cage in N4 = {137/146/236} (cannot be {128/245} which clash with R6C12), no 5,8
20b. Killer quad 1,2,3,4 in 11(3) cage and R6C12, locked for N4
20c. 4 in N4 only in R456C1, locked for C1

21. R4C2 = 8 (hidden single in N4)
21a. 5,9 in N4 only in R56C3, locked for C3

22. 8 in N2 only in R3C456, locked for R3
22a. 8 in C1 only in 20(3) cage in N1 = {389/578}, no 6
22b. 8,9 of {389} must be in R12C1 -> no 3 in R12C1

23. R2C3 + R3C23 (step 11) = {127/136} (cannot be {145} because 1,5 only in R3C2, cannot be {235} which clashes with 20(3) cage) -> R3C2 = 1
23a. R3C23 = {27/36}, no 4

24. R1C3 = 4 (hidden single in N1)
24a. R12C2 = 11 = {29/56}, no 3,7

25. R3C2 = 1 -> 14(4) cage at R2C3 = {1247/1256/1346} (cannot be {1238} because R4C3 only contains 5,6,7), no 8
25a. 7 of {1247} must be in R4C3 -> no 7 in R2C3 + R3C4, clean-up: no 2 in R3C3 (step 23a)

26. 12(3) cage at R6C1 (step 16) = {237/246}, 2 locked for R6 and N4
26a. 2 in 41(8) cage at R6C3 only in R7C456, locked for R7 and N8, clean-up: no 7 in R9C7 (step 5)

27. 17(3) cage in N3 = {269/278/359/368/458/467} (cannot be {179} which clashes with R7C9), no 1

28. 11(3) cage in N4 (step 20a) = {137/146}
28a. 6 of {146} must be in R5C2 -> no 6 in R45C1
28b. 6 in C1 only in R78C1, locked for N7, clean-up: no 3 in R8C1 (step 9)

29. 45 rule on N3 3 innies R2C7 + R3C78 = 18 = {279/369/378} (cannot be {567} which clashes with R4C7), no 5
29a. 9 of {369} must be in R3C8 -> no 6 in R3C8
29b. R2C7 + R3C8 contains one of 8,9 -> R3C6 = {89}
29c. 6 in 30(4) cage at R2C7 only in R24C7, locked for C7
29d. 7 of 30(4) cage at R2C7 only in R24C7 + R3C8, CPE no 7 in R1C7

30. 10(3) cage in N2 = {127/136/235}
30a. 1 in N3 must be in 10(3) cage = {127/136} (cannot be {145} = [514] which clashes with 10(3) cage in N2, ALS block), no 4,5
30b. 6,7 of {127/136} must be in R1C8 (R1C78 cannot be {12/13} which clash with 10(3) cage in N1, ALS block) -> R1C8 = {67}, no 6,7 in R2C8
30c. Naked triple {123} in R13C7 + R2C8, locked for N4

31. 4,5 in N3 only in 17(3) cage (step 27) = {458} (only remaining combination), locked for C9 and N3, clean-up: no 1 in R9C8

32. Naked pair {67} in R24C7, locked for C7 and 30(4) cage at R2C7 -> R3C8 = 9, R3C6 = 8

33. 9 in C9 only in R45C9 -> 19(3) cage in N6 = {289/379/469}
33a. 4,8 of {289/469} must be in R5C8 -> no 2,6 in R5C8

34. 9 in N2 only in R2C456, locked for R2, clean-up: no 2 in R1C2 (step 24a)
34a. 2 in N1 only in R2C23, locked for R2

35. 2 in N3 only in R13C7, locked for C7 -> R9C7 = 8, R7C9 = 1 (step 5)
35a. 17(3) cage at R8C6 (step 18a) = {458} (only remaining combination) -> R8C6 = 5, R9C6 = 4, R9C4 = 1

36. 11(3) cage at R6C8 (step 19) = {137/146}
36a. Killer pair 6,7 in R4C7 and R6C89, locked for N6

37. 19(3) cage in N6 (step 33) = {289} (only remaining combination) -> R5C8 = 8, R45C9 = {29}, locked for C9 and N6, clean-up: no 7 in R8C8, no 7 in R9C8

38. 7 in N9 only in R89C9, locked for C9
38a. 11(3) cage at R6C8 (step 36) = {137/146}
38b. R6C9 = {36} -> no 3,6 in R6C8

39. 7 in 38(7) cage at R2C4 only in R2C456 + R3C3, CPE no 7 in R2C1 + R3C5

40. 6 in R3 only in R3C345, CPE no 6 in R2C456

41. 38(7) cage at R2C4 = {1256789/2345789} (cannot be {1346789} which clashes with R2C8 because 3 of {1346789} must be in R3C7) -> R3C7 = 2
41a. 1 of {1256789} must be in R4C8 -> no 1 in R2C56

42. R2C8 = 1 (hidden single in R2), R1C7 = 3, R1C8 = 6 (step 30a), R2C7 = 7, R4C7 = 6, clean-up: no 5 in R2C2 (step 24a), no 3 in R8C9, no 3 in R9C9

43. Naked pair {23} in R89C8, locked for C8 -> R4C8 = 4, R6C8 = 7, R6C9 = 3 (step 36), R6C12 = [42], R7C1 = 6 (step 26), R9C3 = 3 (step 4), R9C8 = 2, R9C9 = 7, R9C5 = 6, R8C5 = 9, R8C4 = 8, R8C12 = [27], R2C2 = 6, R1C2 = 5 (step 24a), R1C9 = 8, R23C3 = [27], R123C1 = [983], R4C3 = 5, R3C4 = 6 (hidden single in R3), R5C2 = 3

44. R2C9 = 4 (hidden single in R2), R3C9 = 5, R3C5 = 4
44a. R3C5 = 4 -> R45C5 = 7 = [25]

45. R5C7 = 1 -> R45C6 = 9 = [36]

and the rest is naked singles.

Solution:
9 5 4 2 1 7 3 6 8
8 6 2 5 3 9 7 1 4
3 1 7 6 4 8 2 9 5
1 8 5 7 2 3 6 4 9
7 3 9 4 5 6 1 8 2
4 2 6 9 8 1 5 7 3
6 4 8 3 7 2 9 5 1
2 7 1 8 9 5 4 3 6
5 9 3 1 6 4 8 2 7


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 Post subject: Re: Assassin 187
PostPosted: Fri Feb 18, 2011 3:21 am 
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Grand Master
Grand Master

Joined: Wed Apr 23, 2008 6:04 pm
Posts: 1895
Location: Lethbridge, Alberta, Canada
The V3 was another fun puzzle; very few tricky steps and not a lot of analysis. It's not much harder than the V2.

Rating Comment:
I'll rate my walkthrough for A87 V3 at Hard 1.5. Although my walkthrough isn’t technically more difficult than for the V2 it felt a bit more difficult until I spotted step 21; then later I had to re-work step 38 and find a not particularly obvious combination elimination.

Here is my walkthrough for A187 V3:
Prelims

a) R78C3 = {18/27/36/45}, no 9
b) R78C7 = {15/24}
c) R89C5 = {29/38/47/56}, no 1
d) R9C12 = {15/24}
e) R9C89 = {39/48/57}, no 1,2,6
f) 19(3) cage in N1 = {289/379/469/478/568}, no 1
g) 6(3) cage in N1 = {123}
h) 8(3) cage at R3C5 = {125/134}
i) 22(3) cage at R4C6 = {589/679}
j) 22(3) cage at R8C4 = {589/679}
k) 8(3) cage at R8C6 = {125/134}
l) 26(4) cage at R2C3 = {2789/3689/4589/4679/5678}, no 1
m) 37(8) cage at R6C3 = {12345679}, no 8

Steps resulting from Prelims
1a. Naked triple {123} in 6(3) cage, locked for N1
1b. 8(3) cage at R3C5 = {125/134}, 1 locked for C5
1c. 22(3) cage at R4C6 = {589/679}, CPE no 9 in R5C4
1d. 22(3) cage at R8C4 = {589/679}, CPE no 9 in R9C5, clean-up: no 2 in R8C5

2. Killer quint 1,2,3,4,5 in R9C12, R9C67 and R9C89, locked for R9, clean-up: R8C5 = {345}

3. 45 rule on R9 3 outies R8C456 = 14 = {149/158/239/248/257/347/356} (cannot be {167} because R8C5 only contains 3,4,5)
3a. 6,7,8,9 only in R8C4 -> R8C4 = {6789}
[There’s also a CCC or IOU available here, similar to the one in A187 V2, but it’s not needed because of the next step.]

4. 22(3) cage at R8C4 = {679} (only remaining combination), CPE no 6,7 in R9C5 -> R9C5 = 8, R8C5 = 3, clean-up: no 4 in 8(3) cage at R3C5, no 6 in R7C3, no 4 in R9C89
4a. 3 in 37(8) cage at R6C3 only in R7C3467, locked for R7

5. Naked triple {125} in 8(3) cage at R3C5, locked for C5

6. 6 in R9 only in R9C34, locked for 22(3) cage, no 6 in R8C3

7. R8C456 (step 3) must contain 3 = {239/347}, no 1,5
7a. 8(3) cage at R8C6 = {125/134}, 1 locked for R9, clean-up: no 5 in R9C12
7b. Naked pair {24} in R9C12, locked for R9 and N7, clean-up: no 5,7 in R78C3
7c. 3 in R9 only in R9C789, locked for N9

8. 45 rule on N7 2 innies R7C1 + R9C3 = 12 = [39/57] -> R7C1 = {35}, R9C3 = {79}
8a. R9C4 = 6 (hidden single in R9)
8b. Naked pair {79} in R8C4 + R9C3, CPE no 7,9 in R8C12
8c. R7C2 + R9C3 = {79} (hidden pair in N7)
8d. 6 in N7 only in R8C123, locked for R8
8e. 6 in 37(8) cage at R6C3 only in R7C3567, locked for R7

9. 45 rule on N9 2 innies R7C9 + R9C7 = 9 = [45/63/81] -> R7C9 = {468}

10. R7C1 = {35} -> 17(3) cage at R6C1 = {359/458} (other combinations don’t contain at least one of 3,5), no 1,2,7, CPE no 5 in R45C1

11. 18(3) cage in N9 = {189/567} (cannot be {279} which clashes with R9C89, cannot be {459} which clashes with R78C7, cannot be {468} which clashes with R7C9), no 2,4
11a. Hidden killer pair 7,9 in R8C4 and R8C89, R8C4 = {79} -> R8C89 must contain one of 7,9 -> 7,9 of 18(3) cage must be in R8C89 -> no 7,9 in R7C8

12. 2 in N9 only in R78C7 = {24}, locked for C7 and N9, clean-up: no 5 in R9C7 (step 9)

13. 16(3) cage at R6C8 = {169/178/268} (cannot be {259/457} because R7C9 only contains 6,8), no 4,5

14. 13(3) cage in N2 = {148/157/247/256/346} (cannot be {139/238} which clash with 6(3) cage in N1, ALS block), no 9
14a. Killer triple 1,2,3 in 6(3) cage in N1 and 13(3) cage in N2, locked for R1

15. 45 rule on R1 2 innies R1C19 = 2 outies R2C28 + 11
15a. Min R2C28 = 3 -> min R1C19 = 14, no 4 in R1C19
15b. Max R1C19 = 17 -> max R2C28 = 6, no 6,7,8,9 in R2C8

16. 1,5 in N8 only in R7C46 + R9C6, CPE no 1,5 in R6C6
16a. 2,4 in N8 only in R7C46 + R8C6, CPE no 2,4 in R6C6

17. 45 rule on R89 4 outies R7C2378 = 20 = {1289/1469/1478/2369/2378/3467} (cannot be {1379} because R7C7 only contains 2,4, cannot be {1568/2468/3458} because R7C2 only contains 7,9, cannot be {2459/2567} because R7C3 only contains 1,3,8), no 5

18. 45 rule on C1 2 outies R56C2 = 1 innies R89C1 + 6
18aa. Max R56C2 = 17 -> max R89C1 = 11 -> R89C1 cannot be [84]
18ab. R56C2 cannot be {79} = 16 (because this clashes with R7C2) -> R89C1 cannot be 10 = [64/82]
18b. -> no 8 in R8C1

19. 18(3) cage in N7 = {189/567}
19a. 8 of {189} must be in R8C2 -> no 1 in R8C2

20. R7C2378 (step 17) = {1289/1469/1478/2369/3467} (cannot be {2378} = [7328] which clashes with R7C1 +R9C3)
[No eliminations from this step.]

21. R7C1 = {35}, R8C1 = {156} -> R78C1 = [35/36/51/56] (cannot be [31] which clashes with R78C3)
21a. 19(3) cage in N1 = {469/478} (cannot be {568} which clashes with R78C1), no 5, 4 locked for C1 and N1 -> R9C12 = [24]

22. 17(3) cage at R6C1 (step 10) = {359} (only remaining combination) -> R7C1 = 3, R6C12 = {59}, locked for R6 and N4, R9C3 = 9 (step 8), R8C4 = 7, R7C2 = 7, clean-up: no 6 in R8C3, no 3 in R9C89

23. Naked pair {18} in R78C3, locked for C3 and N7

24. Naked pair {57} in R9C89, locked for R9 and N9 -> R9C67 = [13], R8C6 = 4 (step 7a), R78C7 = [42], R7C5 = 9, R7C9 = 6 (step 9)
24a. 16(3) cage at R6C8 (step 13) = {268} (only remaining combination) -> R6C89 {28}, locked for R6 and N6

25. 1 in C1 only in R45C1, locked for N4
25a. 15(3) cage in N4 = {168} (only remaining combination), locked for N4

26. 7 in C1 only in 19(3) cage in N1 (step 21a) = {478} (only remaining combination), locked for N1

27. Naked pair {16} in R45C1, locked for C1 and N4 -> R5C2 = 8, R8C12 = [56], R6C12 = [95], R3C2 = 9
27a. 22(3) cage at R4C6 = {589/679}
27b. 8 of {589} must be in R4C6 -> no 5 in R4C6

28. 26(4) cage at R2C3 = {3689/4589/4679} (cannot be {2789} because R2C3 only contains 5,6), no 2
28a. R23C3 = {56}, CPE no 5 in R3C4
28b. 8 of {3689} must be in R3C4 -> no 3 in R3C4
[With hindsight after step 21a there was
5 in N1 only in R2C3 + R3C23, CPE no 5 in R3C4 + R4C3.]

29. 13(3) cage in N2 (step 14) = {157/247/256/346} (cannot be {148} which clashes with R3C4), no 8

30. 9 in N2 only in R2C46, locked for R2 and 36(7) cage at R2C4, no 9 in R4C8
30a. 8 in N2 only in R23C46, CPE no 8 in R3C7

31. 2 in N4 only in R4C2 + R5C3, CPE no 2 in R4C4
31a. 13(3) cage at R4C4 = {139/148/238/247} (cannot be {157} which clashes with 8(3) cage at R3C5, ALS block because {15} only in R45C4), no 5
31b. 8,9 of {139/148/238} only in R4C4 -> no 1,3 in R4C4
31c. 1 of {148} must be in R5C4, 4 of {247} must be in R4C4 -> no 4 in R5C4

32. Naked pair {56} in R23C3, CPE no 5,6 in R2C456

33. 13(3) cage in N2 (step 29) = {157/256/346} (cannot be {247} which clashes with R2C5)
33a. 7 of {157} must be in R1C5 -> no 7 in R1C6

34. 8 in C7 only in R12C7, locked for N3
34a. 14(3) cage in N3 = {149/239/347} (cannot be {257} which clashes with R9C9), no 5
34b. R1C9 = {79} -> no 7 in R23C9

35. 14(3) cage in N6 = {149/347/356} (cannot be {167} which clashes with R6C7)
35a. 6 of {356} must be in R5C8 -> no 5 in R5C8

36. 45 rule on N3 3 innies R2C7 + R3C78 = 16 = {178/268/358/367/457}
36a. 8 of {178} must be in R2C7 -> no 1 in R2C7
36b. 2,3 of {268/367} must be in R3C8 -> no 6 in R3C8
36c. 3,4 of {358/457} must be in R3C8 -> no 5 in R3C8

37. 24(4) cage at R2C7 = {1689/2589/2679/3489/3579/3678/4569/4578}
37a. 9 of {1689} must be in R4C7 -> no 1 in R4C7

38. 36(7) cage at R2C4 = {1236789/1245789/2345679} (cannot be {1345689} because R2C456 = [849/948] clashes with R3C4)
38a. 8,9 of {1236789/1245789} must be in R2C46 -> no 1 in R2C4
38b. 2 of 36(7) cage must be in R2C46 + R4C2, CPE no 2 in R2C2

39. Naked triple {123} in 6(3) cage, 2 locked for R1

40. 13(3) cage in N2 (step 33) = {157/346}
40a. {157} can only be [175] -> no 5 in R1C4
40b. Killer pair 4,7 in 13(3) cage and R2C5, locked for N2 -> R3C4 = 8

41. R7C4 = 5 (hidden single in C4), R7C6 = 2

42. Naked triple {239} in R2C46 + R4C2, locked for 36(7) cage at R2C4, no 3 in R4C8, CPE no 3 in R2C2 -> R2C2 = 1
42a. Naked pair {23} in R1C23, locked for R1

43. 13(3) cage in N2 (step 40) = {157} (only remaining combination) = [175] -> R1C1 = 8, R1C9 = 9, R1C78 = [64], R2C8 = 5 (cage sum), R2C3 = 6, R3C3 = 5, R2C5 = 4, R23C1 = [74], R2C7 = 8, R3C5 = 2, R9C89 = [75]

44. 14(3) cage in N3 (step 34) = {239} (only remaining combination) -> R23C9 = [23]

and the rest is naked singles.

Solution:
8 3 2 1 7 5 6 4 9
7 1 6 9 4 3 8 5 2
4 9 5 8 2 6 7 1 3
1 2 3 4 5 8 9 6 7
6 8 7 2 1 9 5 3 4
9 5 4 3 6 7 1 2 8
3 7 1 5 9 2 4 8 6
5 6 8 7 3 4 2 9 1


Last edited by Andrew on Wed Apr 20, 2011 9:20 pm, edited 1 time in total.

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 Post subject: Re: Assassin 187
PostPosted: Fri Feb 18, 2011 3:36 am 
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Grand Master
Grand Master

Joined: Wed Apr 23, 2008 6:04 pm
Posts: 1895
Location: Lethbridge, Alberta, Canada
The V4 was definitely harder than the other two variants but still worth trying. Maybe someone will find a better way to continue than my step 10. Once the puzzle had been cracked in step 15 the "endgame" was much shorter than for V2 and V3.

I found an interesting variant of a technique:
in step 9a, which uses the CCC concept to show that the overlapping 21(3) and hidden 21(3) cages cannot have the same combination. It was only while checking my walkthrough today that I spotted step 9b, a further application of step 9a, which simplified the permutation analysis in step 10.

Rating Comment:
I'll rate my walkthrough for A187 V4 at 1.75 based on fairly heavy combination analysis in step 10 and a short forcing chain.

Børge wrote:
When scoring all three puzzles SudokuSolver did NOT use chains or T&E for any of the three puzzles
Well I used one short forcing chain; maybe there was an alternative way to do step 15c. It's sometimes hard to draw a dividing line between chains and heavy combination/permutation analysis.
Here is my walkthrough for A187 V4:
Prelims

a) R78C3 = {16/25/34}, no 7,8,9
b) R78C7 = {14/23}
c) R89C5 = {15/24}
d) R9C12 = {19/28/37/46}, no 5
e) R9C89 = {29/38/47/56}, no 1
f) 6(3) cage in N1 = {123}
g) 20(3) cage at R3C5 = {389/479/569/578}, no 1,2
h) 10(3) cage in N3 = {127/136/145/235}, no 8,9
i) 19(3) cage in N4 = {289/379/469/478/568}, no 1
j) 21(3) cage in N6 = {489/579/678}, no 1,2,3
k) 21(3) cage at R8C6 = {489/579/678}, no 1,2,3
l) 41(8) cage at R6C3= {12356789}, no 4
m) 32(7) = {1234589/1234679/1235678} must contain 1,2,3

1. Naked triple {123} in 6(3) cage, locked for N1

2. 45 rule on R9 3 outies R8C456 = 21 = {489/579} (cannot be {678} because no 6,7,8 in R8C5) -> R8C5 = {45}, R8C46 = {789}, 9 locked for R8 and N8, clean-up: no 4,5 in R9C5
2a. 9 in 41(8) cage at R6C3 only in R6C34567, locked for R6

3. 45 rule on N7 2 innies R7C1 + R9C3 = 12 = {39/48/57}, no 1,2,6

4. 45 rule on N9 2 innies R7C9 + R9C7 = 14 = {59/68}
4a. R9C89 = {29/38/47} (cannot be {56} which clashes with R7C9 + R9C7), no 5,6

5. 15(3) cage in N9 = {159/168/267/357} (cannot be {249/348} which clash with R78C7, cannot be {258/456} which clash with R7C9 + R9C7), no 4

6. 45 rule on N1 2 outies R3C4 + R4C3 = 1 innie R3C3
6a. Max R3C3 = 9 -> max R3C4 + R4C3 = 9, no 9 in R3C4 + R4C3

7. 45 rule on N3 2 outies R3C6 + R4C7 = 1 innie R3C7
7a. Min R3C6 + R4C7 = 3 -> min R3C7 = 3
7b. Max R3C7 = 9 -> max R3C6 + R4C7 = 9, no 9 in R3C6 + R4C7

8. 45 rule on C12 4 innies R1234C2 = 14 = {1238/1247/1256/1346/2345}, no 9
8a. 1,2,3 of {1238} must be in R124C2 -> no 8 in R4C2

9. R8C456 (step 2) = {489/579}, 21(3) cage at R8C6 = {489/579/678}
9a. R8C456 and 21(3) cage at R8C6 = {489/579/678} cannot have the same combination because they share cell R8C6 and R9C6 “sees” R8C456 (this is a variant on CCC) -> at least one of the combinations must contain 7 (and no 7 in R9C7) -> must have 7 in R8C46 + R9C6, locked for N8.
9b. Because 7 only in R8C46 + R9C6, either R8C456 or 21(3) cage at R8C6 must be {489} -> must have 4 in R8C5 + R9C6, locked for N9
9c. Consider permutations for the 21(3) cage
9ca. {489} can only be [948] (because R8C456 must be {579} using step 9a)
9cb. {579} can only be [975] (because R8C456 must be {489} using step 9a)
[Permutations for {678} don’t do anything at this stage.]
9d. -> no 5 in R9C6, no 9 in R9C7, clean-up: no 5 in R7C9 (step 4)
9e. 7 in 41(8) cage at R6C3 only in R6C34567, locked for R6

10. 5 in R9 only in R9C347, R9C34 must total 9,10,11 and R9C67 must total 12,13,14
10a. 45 rule on R9 5 innies R9C34567 = 24 = {12579/13578/14568/24567} (cannot be {13569} because 21(3) cage at R8C6 cannot contain both of 5,6, cannot be {23568} because 21(3) cage at R8C6 cannot contain both of 5,6 or 5,8 and if R9C67 = {68} then R9C34 = {35} totals less than 9)
10b. Consider permutations for R9C34567
10ba. {12579} = 9{12}[75]
10bb. {13578} => R9C67 = [75] (because 21(3) cage at R8C6 cannot contain both of 5,8 and cannot be [78] because no 6 in R8C6), R9C5 = 1, R9C34 = {38} = 11 => R8C4 = 7 (cage total) clashes with R9C6 so cannot be {13578}
10bc. 1 of {14568} must be in R9C5 -> R8C5 = 5 -> R9C3 = 5 (because 21(3) cage at R8C6 cannot contain 5 and one of 4,6,8) => {14568} = [56148]
10bd. 2 of {24567} must be in R9C5 -> R8C5 = 4 => R9C3 = 4 => {24567} = [45276/46275] (only permutations because 21(3) cage at R8C6 cannot contain both of 5,6)
10c. -> no 3,7,8 in R9C3, no 3,8 in R9C4, no 6,8 in R9C6, clean-up: no 4,5,9 in R7C1 (step 3)
10d. R9C34567 = {12579/14568/24567}
10e. 3 in N8 only in R7C456, locked for R7 and 41(8) at R6C3, no 3 in R6C34567, clean-up: no 4 in R8C3, no 2 in R8C7, no 9 in R9C3 (step 3)

11. R9C34567 (step 10d) = {14568/24567}, 4,6 locked for R9, clean-up: no 7 in R9C89
11a. Killer pair 2,8 in R9C34567 and R9C89, locked for R9

12. R78C7 = {14} (only remaining combination, cannot be {23} which clashes with R9C89), locked for C7 and N9
12a. 15(3) cage in N9 (step 5) = {267/357}, no 8,9
12b. Max R3C6 + R4C7 = 9 (step 7b) -> no 8 in R3C6

13. 2 in N7 only in 16(3) cage or R78C3 = {25} -> 16(3) cage can only contain 5 if it also contains 2 -> 16(3) cage = {169/259/268/367} (cannot be {358/457} which contain 5 but not 2, cannot be {178/349} which clash with R9C12), no 4
13a. 9 of {169/259} must be in R7C2 -> no 1,5 in R7C2

14. Hidden killer pair 3,4 in R6C12 and R6C89 for R6, R6C12 can only contain one of 3,4 (13(3) cage at R6C1 cannot contain both of 3,4 in R6C12 because there’s no 6 in R7C1), R6C89 can only contain one of 3,4 -> R6C12 and R6C89 must each contain one of 3,4
14a. 13(3) cage at R6C1 = {148/238/247} (cannot be {157/256} which don’t contain 3 or 4, cannot be {346} because 3,4,6 only in R6C12), no 5,6
14b. 1,4 of {148} must have been in R6C12 (because of hidden killer pair) -> no 8 in R6C12
14c. 17(3) cage at R6C8 = {359/368/458} (cannot be {269} which doesn’t contain 3 or 4), no 1,2
14d. R4C8 = 1 (hidden single in N6)

15. 4 in R7 only in R7C37
15a. 45 rule on R89 4 outies R7C2378 = 19 = {1459/2458/2467/3457} (cannot be {1468} = 8{14}6 because 16(3) cage in N7 (step 13) = 8{26} clashes with 15(3) cage in N9 (step 12a) = 6{27})
15b. 8 of {2458} must be in R7C2, 2 of {2467} must be in R7C3 (R78C3 cannot be [61] which clashes with R78C7 = [41]) -> no 2 in R7C2, no 6 in R7C3, clean-up: no 1 in R8C3
15c. Consider the combinations for R7C2378
15ca. {1459} => R7C2 = 9, R7C8 = 5 => R8C89 = {37} (step 12a), locked for R8 => no 3 in R8C3 => no 4 in R7C3
15cb. All other combinations for R7C2378 must have 4 in R7C7
15d. -> R7C7 = 4, R8C7 = 1, clean-up: no 3 in R8C3

16. R9C3 = 4 (hidden single in N7), R7C1 = 8 (step 3), R9C6 = 7, clean-up: no 3 in R9C12, no 6 in R9C7 (step 4)
16a. 8 in 41(8) cage at R6C3 only in R6C34567, locked for R6

17. 21(3) cage at R8C6 = {579} (only remaining combination) -> R8C6 = 9, R9C7 = 5, R7C9 = 9 (step 4), R8C4 = 8, R8C5 = 4 (step 2), R9C5 = 2, R9C4 = 6 (hidden single in R9)

18. Naked triple {135} in R7C456, locked for R7 and 41(8) cage at R6C3, no 1,5 in R6C3456 -> R7C3 = 2, R8C3 = 5
18a. Naked pair {38} in R9C89, locked for N9

19. 17(3) cage at R6C8 (step 14c) = {359} (only remaining combination) -> R6C89 = {35}, locked for R6 and N6

20. R6C12 = {14} (hidden pair in R6), locked for N4

21. 2 in C1 only in R45C1, locked for N4
21a. 19(3) cage in N4 = {289} -> R5C2 = 8, R45C1 = {29}, locked for C1 and N4 -> R9C12 = [19], R6C12 = [41]

22. Naked pair {23} in R12C2, locked for C2 and N1 -> R1C3 = 1

23. Naked triple {567} in 18(3) cage, locked for C1 and N1 -> R3C2 = 4, R8C1 = 3
23a. R4C2 = 5 (hidden single in N4)

24. 32(7) cage at R2C4 contains 5 = {1234589/1235678}, 2 locked for R2 and N2 -> R2C2 = 3, R1C2 = 2
24a. R3C7 = 3 (hidden single in 32(7) cage)
24b. Naked pair {89} in R23C3, CPE no 8,9 in R2C456
24c. 32(7) cage = {1235678} (only remaining combination, cannot be {1234589} because 8,9 only in R3C3) -> R3C3 = 8, R2C456 = {267}, locked for R2 and N2 -> R2C1 = 5, R2C3 = 9, R2C7 = 8, R2C8 = 4 , R2C9 = 1

25. Naked pair {15} in R3C46, locked for R3 and N2 -> R3C5 = 9, R45C5 = 11 = [65/83],
25a. R7C5 = 1 (hidden single in C5)

26. R2C8 = 4 -> R1C78 = 14 = [95], R6C89 = [35], R9C89 = [83]

27. R5C8 = 9 (hidden single in C8), R45C9 = [84] (hidden pair in C9), R4C5 = 6, R5C5 = 5 (step 25), R2C456 = [276], R6C56 = [82], R45C1 = [92], R1C456 = [438]

28. Naked pair {37} in R4C34, locked for R4, CPE no 3,7 in R5C3 -> R5C3 = 6, R6C3 = 7, R4C3 = 3, R4C4 = 7, R5C4 = 1 (cage sum), R3C46 = [51], R4C7 = 2, R3C8 = 6 (cage sum)

and the rest is naked singles.

Solution:
6 2 1 4 3 8 9 5 7
5 3 9 2 7 6 8 4 1
7 4 8 5 9 1 3 6 2
9 5 3 7 6 4 2 1 8
2 8 6 1 5 3 7 9 4
4 1 7 9 8 2 6 3 5
8 6 2 3 1 5 4 7 9
3 7 5 8 4 9 1 2 6
1 9 4 6 2 7 5 8 3


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