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 Post subject: Assassin 261
PostPosted: Fri May 31, 2013 3:07 am 
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Grand Master
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Joined: Wed Apr 16, 2008 1:16 am
Posts: 1044
Location: Sydney, Australia
Haven't had one like this in a while. I found it has a one-trick pony which is available from the start [edit: not true, it's not valid so I was tricked. I did intend to post an optimised version of how SudokuSolver does it (with Scoring routines selected) but couldn't get it done. Thanks to Andrew for finding a valid way in!] but only found it after exploring lots of other tangents. Am sure SudokuSolver can't do it my way so will be some flexibility for other approaches. I originally started with a similiar cage pattern but that was a one-trick pony that had no other reasonable solution so didn't appeal. A261 gets a SudokuSolver score of 1.25

Assassin 261

Image

code: paste into solver:
3x3::k:3840:3840:3840:3329:3329:4610:4610:4610:3587:3840:8196:2821:3078:2055:2312:2312:4610:3587:8196:2821:3078:2055:6921:6921:6921:2312:4362:8196:2821:4619:6921:6921:3852:5645:4362:4362:8196:3086:4619:3852:3852:3852:5645:2319:2319:4112:8196:3086:4619:2833:3852:5645:3346:3346:4112:3091:8212:8212:2833:8212:5645:3346:4885:4112:3091:3606:8212:8212:8212:6679:4885:4885:4112:3091:3606:2584:2584:6679:6679:6679:4885:
solution:
+-------+-------+-------+
| 3 6 1 | 9 4 5 | 2 7 8 |
| 5 9 2 | 8 7 3 | 1 4 6 |
| 7 8 4 | 1 2 6 | 3 5 9 |
+-------+-------+-------+
| 8 1 3 | 7 9 4 | 5 6 2 |
| 6 7 9 | 3 5 2 | 4 8 1 |
| 4 2 5 | 6 8 1 | 7 9 3 |
+-------+-------+-------+
| 9 5 7 | 2 3 8 | 6 1 4 |
| 2 4 6 | 5 1 9 | 8 3 7 |
| 1 3 8 | 4 6 7 | 9 2 5 |
+-------+-------+-------+
Cheerio
Ed


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 Post subject: Re: Assassin 261
PostPosted: Mon Jun 03, 2013 4:28 am 
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Grand Master
Grand Master

Joined: Wed Apr 23, 2008 6:04 pm
Posts: 1895
Location: Lethbridge, Alberta, Canada
Thanks Ed for an interesting and challenging Assassin!

Ed wrote:
I found it has a one-trick pony which is available from the start but only found it after exploring lots of other tangents.
I found several interesting steps but no breakthrough ones which were available immediately after the Prelims, so I probably didn't find Ed's one-trick pony.

I must admit that I tend to find puzzles with diagonally-connected cages harder, partly because they are harder to colour with the minimum number of colours, but in this case I don't think those connections made it any harder to solve.

Thanks Ed for pointing out a couple of typos.
Here is my walkthrough for Assassin 261:
Prelims

a) R1C45 = {49/58/67}, no 1,2,3
b) R12C9 = {59/68}
c) 12(2) cage at R2C4 = {39/48/57}, no 1,2,6
d) 8(2) cage at R2C5 = {17/26/35}, no 4,8,9
e) 12(2) cage at R5C2 = {39/48/57}, no 1,2,6
f) R5C89 = {18/27/36/45}, no 9
g) R67C5 = {29/38/47/56}, no 1
h) R89C3 = {59/68}
i) R9C45 = {19/28/37/46}, no 5
j) 11(3) cage at R2C3 = {128/137/146/236/245}, no 9
k) 9(3) cage at R2C6 = {126/135/234}, no 7,8,9
l) 26(4) cage at R8C7 = {2789/3689/4589/4679/5678}, no 1
m) 15(5) cage at R4C6 = {12345}
n) 32(5) cage at R2C2 = {26789/35789/45689}, no 1

1. Naked quint {12345} in 15(5) cage at R4C6, locked for N5, clean-up: no 6,7,8,9 in R7C5

2. 45 rule on C12 3 outies R126C3 = 8 = {125/134}, 1 locked for C3 and N1, clean-up: no 3,4,5 in R5C2
2a. 5 of {125} must be in R6C3 -> no 5 in R12C3

3. 45 rule on N69 2(1+1) outies R3C9 + R9C6 = 16 = [79/88/97]

4. 45 rule on N7 1 innie R7C3 = 1 outie R6C1 + 3, no 7,8,9 in R6C1, no 2,3 in R7C3

5. 45 rule on N9 1 outie R9C6 = 2 innies R7C78
5a. Max R7C78 = 9, no 9 in R7C78

6. 45 rule on N6789 3(1+2) outies R3C9 + R6C15 = 21
6a. Max R3C9 = 9 -> min R6C15 = 12, no 1,2 in R6C1, no 6 in R6C5 (because R6C15 cannot be [66]), clean-up: no 4,5 in R7C3 (step 4), no 5 in R7C5
6b. 6 in N5 only in R4C45 + R6C4, CPE no 6 in R4C3

7. R4C2 = 1 (hidden single in N4), R2C3 + R3C2 = 10 = [28/37/46]
7a. R1C3 = 1 (hidden single in C3)

8. 12(3) cage at R7C2 = {237/246/345}, no 8,9

9. 45 rule on C123 2 outies R26C4 = 1 innie R7C3 + 7
9a. Min R7C3 = 6 -> min R26C4 = 13, no 3 in R2C4, clean-up: no 9 in R3C3

10. 45 rule on N1 3 remaining innies R2C3 + R3C13 = 20 = {389/479/569/578}, no 2

11. 2 in R126C3 (step 2) = [125] or 18(3) cage at R4C3 -> 18(3) cage = {279/369/378/468} (cannot be {459/567}, locking-out cages), no 5

12. 15(4) cage at R1C1 = {1239/1248/1257/1347/1356}
12a. 45 rule on C12 2 remaining innies R35C2 = 15 = [69/78/87]
12b. Consider combinations for R35C2
R35C2 = [69] => 9 in 32(5) cage at R2C2 must be in R2C2 + R3C1
or R35C2 = {78} => R2C3 = {23} (step 7) => 15(4) cage cannot be {1239}
-> 15(4) cage = {1248/1257/1347/1356}, no 9
12c. 9 in N1 only in R2C2 + R3C1, locked for 32(5) cage at R2C2, no 9 in R45C1 + R6C2
12d. R2C3 + R3C13 (step 10) contains 9 = {389/479/569}

13. 2 in R126C3 = [125] or 18(3) cage at R4C3 -> 18(3) cage = {279/369/378/468} (step 11)
13a. 9 in N4 only in 18(3) cage or 12(2) cage at R5C2 = [93] -> 18(3) cage = {279/369} (cannot be {378/468}, locking-out cages using both 2 in C3 and 9 in N4), no 4,8
13b. 9 in N4 only in 18(3) cage or 12(2) cage at R5C2 = [93] -> 18(3) cage = {369} can only be {39}6 (locking-out cages), no 6 in R5C3
13c. Killer pair 2,3 in R26C3 and 18(3) cage, locked for C3, clean-up: no 9 in R2C4
13d. 8 in N4 only in R45C1 + R56C2, CPE no 8 in R2C2
13e. 8 in N5 only in R4C45 + R6C5, CPE no 8 in R3C5

14. 6 in C3 only in R789C3, locked for N7
14a. 12(3) cage at R7C2 (step 8) = {237/345}, 3 locked for C2 and N7

15. Hidden killer pair 6,8 in R37C3 and R89C3 for C3, R89C3 contains both or neither of 6,8 -> R37C3 must contain both or neither of 6,8, there's no 6 in R3C3 -> no 8 in R7C3, clean-up: no 5 in R6C1 (step 4)

16. 45 rule on C1 3 remaining outies R126C2 = 17 = {269/278/458} (cannot be {467} which clashes with R35C2)
16a. 9 of {269} must be in R2C2 -> no 6 in R2C2
16b. 7 of {278} must be in R2C2 -> no 7 in R16C2

17. R2C3 + R3C2 (step 7) = [28/37/46]
17a. R2C3 + R3C13 (step 12d) = {479/569} (cannot be {389} = [938] because R2C3 + R3C2 = [46] clashes with R2C4 + R3C3 = [48]), no 3,8, clean-up: no 4 in R2C4
17b. 15(4) cage at R1C1 (step 12b) = {1248/1347/1356} (cannot be {1257} which clashes with R2C3 + R3C13)
17c. R2C3 + R3C2 = [28/37] (cannot be [46] which clashes with 15(4) cage), clean-up: no 9 in R5C2 (step 12a), no 3 in R6C3
[Cracked. The rest is fairly straightforward.]

18. Naked pair {78} in R35C2, locked for C2
18a. 12(3) cage at R7C2 = {345} (only remaining combination), locked for C2 and N7 -> R2C2 = 9, clean-up: no 5 in R1C9, no 9 in R89C5
18b. Naked pair {68} in R89C3, locked forN7, clean-up: no 3 in R6C1 (step 4)

19. 9 in N4 only in R45C3, locked for C3 -> R7C3 = 7, R6C1 = 4 (step 4), R6C3 = 5, R5C2 = 7, R3C2 = 8, R2C3 = 2 (step 7), R1C2 = 6, R6C2 = 2, R3C3 = 4, R2C4 = 8
19a. R1C23 = [61] = 7 -> R12C1 = 8 = {35}, locked for C1 -> R3C1 = 7, R3C9 = 9, R1C9 = 8, R2C9 = 6, R9C6 = 7 (step 3)
19b. R1C45 = {49} (only remaining combination), locked for R1 and N2
19c. R2C5 = 7 (hidden single in N2), R3C4 = 1
[Routine clean-ups omitted from here]

20. 45 rule on R1 2 remaining outies R2C18 = 9 = [54], R1C1 = 3
20a. R2C67 = {13} = 4 -> R3C8 = 5
20b. Naked pair {27} in R1C78, locked for R1 and N3 -> R1C6 = 5, R3C7 = 3, R2C67 = [31]

21. R6C6 = 1, R45C6 = {24}, locked for C6 and N5, R3C56 = [26]

22. R3C567 = [263] = 11 -> R4C45 = 16 = [79], R1C45 = [94], R45C3 = [39], R6C45 = [68], R7C5 = 3

23. 13(3) cage at R6C8 = {139} (only remaining combination) -> R6C89 = [93], R7C8 = 1

24. R3C9 = 9 -> R4C89 = 8 = [62], R5C8 = 8, R5C9 = 1

25. R789C9 = {457} = 16 -> R8C8 = 3, R9C8 = 2, R9C4 = 4, R9C5 = 6

and the rest is naked singles.

Rating Comment:
I thought about rating my walkthrough at 1.5 but I think I'll go for Hard 1.5; steps 13a and 17a were tricky and hard to find, even after I'd found the fairly obvious step 11. Maybe one doesn't expect to find two different ways to use locking-out cages on the same cage?!


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