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 Post subject: Assassin 451
PostPosted: Thu Feb 01, 2024 6:03 am 
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Grand Master
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Joined: Wed Apr 16, 2008 1:16 am
Posts: 1044
Location: Sydney, Australia
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Assassin 451
This started life based on a puzzle groston showed us but then went through many transformations to get the right balance of big and small cages. The number of bigger cages that didn't cross between nonets is what made it so hard to get right. I had a hard time cracking this version but easy enough to do once you see the way. One key elimination. Perfect follow-up to a450. It gets 1.40. JSudoku has no trouble (using my bespoke solver order).

triple click code:
3x3::k:6400:6400:6400:5633:5633:5633:4354:3331:3331:6400:3844:3844:5633:7941:3334:4354:4354:3335:6400:3844:5640:5640:7941:3334:1289:1289:3335:3850:3850:5640:5640:7941:4619:4620:4620:3335:3850:7941:7941:7941:4619:4619:4620:9485:3335:3850:3342:3342:1295:1295:2576:2576:9485:9485:4113:4113:1298:4115:4115:2576:5908:5908:9485:3861:4113:1298:4115:4374:4374:5908:5908:9485:3861:5399:5399:5399:5399:4374:4374:9485:9485:
solution:
+-------+-------+-------+
| 2 7 3 | 4 6 9 | 1 5 8 |
| 4 1 8 | 3 2 5 | 7 9 6 |
| 9 6 5 | 7 1 8 | 2 3 4 |
+-------+-------+-------+
| 3 5 2 | 8 4 7 | 9 6 1 |
| 1 8 7 | 9 5 6 | 3 4 2 |
| 6 4 9 | 2 3 1 | 5 8 7 |
+-------+-------+-------+
| 5 2 1 | 6 9 4 | 8 7 3 |
| 7 9 4 | 1 8 3 | 6 2 5 |
| 8 3 6 | 5 7 2 | 4 1 9 |
+-------+-------+-------+
Cheers
Ed


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 Post subject: Re: Assassin 451
PostPosted: Sun Feb 04, 2024 9:21 pm 
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Grand Master
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Joined: Wed Apr 23, 2008 6:04 pm
Posts: 1895
Location: Lethbridge, Alberta, Canada
Thanks Ed for your latest operation. My solving path was shorter than usual; it's good to get a mix of Assassin's like this and really challenging ones. I'll be interested to see how my breakthrough steps compare with your "one key elimination".

Here's how I solved Assassin 451:
Prelims

a) R1C89 = {49/58/67}, no 1,2,3
b) R23C6 = {49/58/67}, no 1,2,3
c) R3C78 = {14/23}
d) R6C23 = {49/58/67}, no 1,2,3
e) R6C45 = {14/23}
f) R78C3 = {14/23}
g) R89C1 = {69/78}
h) 10(3) cage at R6C6 = {127/136/145/235}, no 8,9
i) 13(4) cage at R2C9 = {1237/1246/1345}, no 8,9

1a. 45 rule on N1 1 innie R3C3 = 5, clean-up: no 8 in R2C6, no 8 in R6C2
1b. 45 rule on N1245 1 innie R6C6 = 1, clean-up: no 4 in R6C45
1c. Naked pair {23} in R6C45, locked for R6 and N5
1d. R6C7 + R7C6 = 9 = {45}/[63/72], no 6,7 in R7C6
1e. 45 rule on N3 2 outies R45C9 = 3 = {12}, locked for C9 and N6
1f. R45C9 = 3 -> R23C9 = 10 = {37/46}
1g. Killer pair 3,4 in R23C9 and R3C78, locked for N3, clean-up: no 9 in R1C89
1h. R1C89 = {58} (cannot be {67} which clashes with R23C9), locked for R1 and N3
1i. 37(7) cage at R5C8 must contain at least one of 1,2 -> R9C8 = {12}
1j. 45 rule on N78 1 innie R7C6 = 1 outies R9C7 = {2345}
1k. 45 rule on N7 2 outies R9C45 = 12 = {39/48/57}, no 1,2,6
1l. 45 rule on N7 2 innies R9C23 = 9 = {18/27/36}/[54], no 9, no 4 in R9C2
1m. 45 rule on N2 3 innies R2C5 + R3C45 = 10 = {127/136/145/235}, no 8,9
1n. 5 of {145} must be in R2C5 -> no 4 in R2C5

2a. 9 in C9 only in R6789C9, locked for 37(7) cage, no 9 in R56C8
2b. 37(7) cage = {1345789/2345689} (cannot be {1246789} because 1,2 only in R9C8) must contain 3,4,5,8,9
2c. Hidden killer pair 6,7 in R23C9 and R6789C9 for C9, R23C9 contains one of 6,7 -> R6789C9 must contain one of 6,7, 37(7) cage only contains one of 6,7 -> no 6,7 in R56C8
2d. Caged X-Wing for 5,8 in R1C89 and 37(7) cage, no other 5,8 in C8
2e. Hidden killer pair 5,8 in R1C8 and R56C8 for C8, R1C8 = {58} -> R56C8 must contain one of 5,8 -> must also contain one of 3,4
2f. 45 rule on N36 4 innies R5C8 + R6C789 = 24 = {3489/3678/4569/4578} (cannot be {3579} which clashes with R6C23)
2g. 45 rule on R6789 1 innie R6C1 = 1 outie R5C8 + 2 -> R5C8 = {345}, R6C1 = {567}
2h. 45 rule on N78 2 remaining outies R69C7 = 9 = [54/63/72] (cannot be [45] because puts 5 in R5C8 + R6C789 when [5487] clashes with R1C8 and cannot be {4569} because 6,9 only then in R6C9) -> R6C7 = {567}, R9C7 = {234}, clean-up: no 5 in R7C6 (step 1d)
2i. R6C23 = {49}/[58] (cannot be {67} which clashes with R6C17, ALS block), no 6,7
2j.Consider permutations for R69C7 = [54/63/72]
R69C7 = [54] => R5C8 + R6C789 = [4587] (cannot be {4569} because 6,9 only then in R6C9)
or R69C7 = [63] => R5C8 = 3, R6C789 = [687]
or R69C7 = [72] => R5C8 + R6C789 = [3768]/[47]{58} (cannot be [57]{48} which clashes with R6C1, step 2g)
-> R5C8 + R6C789 = 3{678}/4{578}, no 5 in R5C8, 7,8 locked for R6 and N6, clean-up: no 5,6 in R6C2
2k. Naked pair {49} in R6C23, locked for R4 and N4
2l. 9 in C9 only in R789C9, locked for N9
2m. 15(4) cage at R4C1 = {1257/1356}, no 8, 1 locked for N4
2n. Consider placement for 7 in N6
R6C7 = 7 => R9C7 = 2 -> 37(7) cage = {1345789}, 7 locked for C9
or R6C9 = 7 -> 37(7) cage = {1345789}
-> R9C8 = 1, 37(7) cage = {1345789}, 7 locked for C9, clean-up: no 3 in R23C9, no 8 in R9C23 (step 1l)
[Cracked, fairly straightforward from here.]
2o. Naked pair {46} in R23C9, locked for C9 and N3, clean-up: no 1 in R3C7
2p. Naked pair {23} in R3C78, locked for R3, 2 locked for N3
2q. 37(7) cage = {1345789} -> R5C8 = 4, R6C789 = {578}, 5 locked for R6 and N6, 3 locked for N9, clean-up: no 3 in R7C6 (step 1d)
2r. R6C1 = 6 -> R4C12 + R5C1 = {135}, 3,5 locked for N4, clean-up: no 9 in R89C1
2s. Naked pair {78} in R89C1, locked for C1 and N7, clean-up: no 2 in R9C23 (step 1l)
2t. Killer pair 3,4 in R78C3 and R9C23, locked for N7
2u. 21(4) cage at R9C2 must contain 3, locked for R9
2v. 4 in C1 only in R123C1, locked for N1
2w. 8 in N1 only in 15(3) cage at R2C2 = {168}, 1,6 locked for N1
2x. R2C5 + R3C45 (step 1m) = {127/136/145} (cannot be {235} because 2,3,5 only in R2C5)
2y. 2,3,5 only in R2C5 -> R2C5 = {235}, R3C45 = {14/16/17}, 1 locked for R3 and N2
2z. 15(3) cage = {168}, 1 locked for R2 -> R2C78 = {79}, locked for R2 and N3, clean-up: no 4,6 in R3C6

[Some clean-ups omitted from here.]
3a. 6 in R1 only in R1C456, locked for N2, clean-up: no 7 in R3C6
3b. R3C45 = {17} (hidden pair in R3), 7 locked for N2 -> R2C5 = 2 (step 2x), R6C45 = [23]
3c. Naked pair {78} in R5C23, locked for R5, N4 and 31(6) cage at R2C5 -> R3C5 = 1
3d. R3C34 = [57], R4C3 = 2 -> R4C4 = 8 (cage sum), clean-up: no 3 in R78C3
3e. R23C5 = [21], R5C23 = {78} -> R4C5 + R5C4 = 13 = [49]
3f. R3C6 = 8 (hidden single in N2) -> R2C6 = 5, R3C2 = 6, R23C9 = [64], R3C1 = 9
3g. R5C56 = [56], R4C6 = 7, R5C17 = [13], R3C78 = [23]
3h. R9C7 = 4, R9C23 (step 1l) = [36], R9C4 = 5 -> R9C5 = 7 (step 1k), R4C12 = [35], R12C1 = [24], R1C23 = [73], R2C4 = 3
3i. R8C6 = 3 (hidden single in N8), R9C7 = 4 -> R8C5 + R9C6 = 10 = [82], R67C6 = [14] -> R6C7 = 5 (cage sum)

and the rest is naked singles.


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 Post subject: Re: Assassin 451
PostPosted: Sat Feb 10, 2024 6:46 pm 
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Grand Master
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Joined: Wed Apr 16, 2008 1:16 am
Posts: 1044
Location: Sydney, Australia
Andrew used sterile instruments whereas I used some blunt trauma! Well done Andrew. I used a different "45" but we worked in the same areas. [Thanks to Andrew for checking my WT]
a451 WT:
Preliminaries by SudokuSolver
Cage 5(2) n7 - cells only uses 1234
Cage 5(2) n3 - cells only uses 1234
Cage 5(2) n5 - cells only uses 1234
Cage 15(2) n7 - cells only uses 6789
Cage 13(2) n3 - cells do not use 123
Cage 13(2) n2 - cells do not use 123
Cage 13(2) n4 - cells do not use 123
Cage 10(3) n568 - cells do not use 89
Cage 13(4) n36 - cells do not use 89

Note: no clean-up done unless stated
1. "45" on n1245: 1 innie r6c6 = 1

2. 5(2)n5 = {23}: both locked for n5 and r6

3. "45" on n3: 2 outies r45c9 = 3 = {12}: both locked for c9 and n6
3a. -> r23c9 = 10 = {37/46}(no 5)

4. killer pair 3,4 in h10(2)n3 and 5(2)n3
4a. both locked for n3

5. 17(3)n3 = {179/269/278}(no 5)

6. 5 in n3 only in 13(2) = {58}: both locked for r1 and 8 for n3

7. 37(7) can have at most one of 1,2 since they are only in r9c8
7a. = {17}/{26}[{34589}]
7b. r9c8 = (12)
7a. note, missing {17} or {26}

8. hidden killer pair 5,8 in c9
8a. ie r6789c9 must have exactly one of 5,8 for c9 since the only other place for them is r1c9 = (58)
8b. 37(7)r5c8 must have both 5,8 (step 7a)
8c. -> r56c8 must have one of 5,8
8d. -> killer pair 5,8 in r156c8: both locked for c8
[alternatively, cage x-wings on both 5 and 8 since both 13(2) rn 37(7) must have both: both 5 & 8 locked for c89]

9. "45" on c9: 4 outies r1569c8 = 18
9a. must have both 5 & 8 for c8
9b. = {1458/2358}(no 6,7,9)

10. "45" on c789: 2 innies r69c7 = 9 = {45}/[63/72]
10a. ie r9c6 = (2345)
10b. Note: putting steps 7a and 10a together: 2 in 9c8 -> no 7 in r5c8 + r6c789

11."45" on r6789: 1 outie r5c8 + 2 = 1 innie r6c1
11a. = [35/46/57]
11b. ie r6c1 = (567), no 8 r5c8

12. "45" on n36: 4 innies r5c8 + r6c789 = 24
12a. but {3579} as [3]{579} is blocked by 5 also in r6c1 (step 11a)
12b. = {3489/3678/4569/4578}(no eliminations yet)

key elimination of 3 from r5c8: a contradiction step
13. 3 in r5c8 has 5 in r6c1 (iodr6789=+2) -> {2358} in h18(4)c8 (step 9b) = [5382] only permutation
13a. -> 7 missing from r6c79 (step 10b)
13b. -> {3489} in h24(4)n6 = [3489] only, but this forces 5 which must be in 37(7) into n9 and h9(2)r69c7 = [45] -> two 5 n9 -> {3489} is blocked
13c. -> no 3 in r5c8
13d. -> no 5 in r6c1
13e. -> h18(4)c8 = {1458} only
13f. -> r9c8 = 1
13g. 4 locked in r56c8 for n6 and 37(7)

14. 4 in c9 only in h10(2)n3 = {46}: both locked for n3 and 6 for c9

15. 5(2)n3 = {23}: both locked for r3, 2 for n3

16. 3 in c9 only in n9: locked for n9
16a. no 6 in r6c7 (h9(2))

17. h24(4)n6 = {4578} only (no 9)
17a. 5,7,8 locked for n6, 8 for 37(7) and r6

18. 9 in r6 only in 13(2) = {49}: both locked for n4 and 4 for r6

19. r6c1 = 6 (hsingle r6)
19a. r5c8 = 4 (hsingle n6)
19b. 15(4)n4 = {135}[6]: 1,3,5 locked for n4

20. 15(2)n7 = {78}: both locked for n7 and c1

21. "45" on n1: 1 innie r3c3 = 5

22. 25(5)n1 = {12679/23479}
22a. 7 locked for r1 and n1, 2 & 9 locked for n1

23. 7 in n3 only in r2: locked for r2

24. "45" on n2: 3 innies r2c5 + r3c45 = 10
24a. but {235} blocked since 2,3 are only in r2c5
24b. {136} blocked since 7 in n2 is only in 13(2) = [67] or in h10(3) (Locking out cages)
24c. = {127/145}(no 3,6,8,9)
24d. must have 2 or 5 which are only in r2c5 -> r2c5 = (25)
24e. 1 locked for n2 and r3

25. 31(6)r2c5 must have three of {2578} for r2c5 + r5c23 and has no 3s available anywhere
25a. = {124789/125689/145678}
25b. has exactly three of {2578} -> no 5,7,8 in r4c5 + r5c4
25c. must have 1 -> r3c5 = 1
25d. must have 8: locked for r5 and n4

26. 18(3)n5: must have 5 for n5
26a. = {459/567}(no 8)

27. r4c4 = 8 (hsingle n5)
27a. -> r3c4 + r4c3 = 9 (cage sum)
27b. = [72] only

on from there
Cheers
Ed


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