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A202 v0.85     SS score 0.85 ◄ Select to see the SS score
A202 v1     SS score 1.18 ◄ Select to see the SS score
A202 v2     SS score 1.82 ◄ Select to see the SS score

Thanks Børge for an interesting cage pattern. It seems designed to give some early results, even for the V2 which I haven't yet tried, followed by some harder work later.


Here is my walkthrough for A202

Prelims

a) R1C12 = {79}
b) R1C34 = {14/23}
c) R23C1 = {29/38/47/56}, no 1
d) R2C23 = {29/38/47/56}, no 1
e) R3C23 = {14/23}
f) R4C12 = {29/38/47/56}, no 1
g) R45C3 = {69/78}
h) R5C12 = {17/26/35}, no 4,8,9
i) R67C9 = {29/38/47/56}, no 1
j) R7C56 = {17/26/35}, no 4,8,9
k) R78C7 = {16/25/34}, no 7,8,9
l) R78C8 = {69/78}
m) R89C5 = {89}
n) R89C6 = {14/23}
o) R89C9 = {39/48/57}, no 1,2,6
p) R9C78 = {16/25/34}, no 7,8,9
q) 29(7) cage at R6C1 = {1234568}, no 7,9
r) Both 45(9) cages = {123456789}

Steps resulting from Prelims
1a. Naked pair {79} in R1C12, locked for R1 and N1, clean-up: no 2,4 in R23C1, no 2,4 in R2C23
1b. Naked pair {89} in R89C5, locked for C5 and N8

2. 45 rule on N1 1 innie R1C3 = 2 -> R1C4 = 3, clean-up: no 3 in R3C23
2a. Naked pair {14} in R3C23, locked for R3

3. 45 rule on N7 1 innie R7C3 = 3, clean-up: no 8 in R2C2, no 8 in R6C9, no 5 in R7C56, no 4 in R8C7

4. 45 rule on N9 1 innie R7C9 = 4 -> R6C9 = 7, clean-up: no 3 in R8C7, no 5,8 in R89C9, no 3 in R9C78
4a. Naked pair {39} in R89C9, locked for C9 and N9, clean-up: no 6 in R78C8
4b. Naked pair {78} in R78C8, locked for C8

5. 7 in N8 only in R7C56 = {17}, locked for R7 and N8 -> R78C8 = [87], clean-up: no 4 in R89C6, no 6 in R8C7
5a. Naked pair {23} in R89C6, locked for C6 and N8

6. Naked triple {456} in R789C4, locked for C4 and 29(7) cage at R6C1, no 4,5,6 in R6C123
6a. Naked triple {128} in R6C123, locked for R6 and N4 -> R6C4 = 9, clean-up: no 3,9 in R4C12, no 7 in R45C3, no 6,7 in R5C12
6b. R9C3 = 7 (hidden single in C3)

7. Naked pair {69} in R45C3, locked for C3 and N4, clean-up: no 5 in R2C2, no 5 in R4C12
7a. Naked pair {47} in R4C12, locked for R4
7b. Naked pair {35} in R5C12, locked for R5
7c. Killer pair 3,5 in R23C1 and R5C1, locked for C1

8. R4C5 = 3 (hidden single in 45(9) cage at R1C5)

9. 9 in 45(9) cage at R1C5 only in R5C78, locked for R5 and N6 -> R45C4 = [96]
9a. 5,6 in 45(9) cage at R1C5 only in R123C5, locked for C5 and N2 -> R6C5 = 4
9b. 8 in 45(9) cage at R1C5 only in R5C679, locked for R5

10. R46C6 = {56} (hidden pair in N5)
10a. R5C78 = {49} (hidden pair in R5)

11. 35(7) cage at R1C6 = {1245689} (doesn’t contain 3 so cannot contain 7), no 7
11a. 2 of 35(7) cage only in R4C789, locked for R4 and N6

12. 9 in R7 only in R7C12, locked for N7
12a. 27(5) cage in N7 contains 7 and 9 = {12789/14679/24579}
12b. 1,4 of {14679} must be in R8C23 -> no 6 in R8C2

13. 15(3) cage in N7 = {168/258} (cannot be {456} which clashes with R9C4 + R9C78, killer ALS block), no 4, 8 locked for N7
13a. 1 of {168} must be in R89C1 (R89C1 cannot be {68} which clashes with R23C9) -> no 1 in R9C2
13b. 5 of {258} must be in R9C2 -> no 2 in R9C2

14. R9C4 = 4 (hidden single in R9)

15. 15(3) cage in N7 (step 13) = {168/258}
15a. Hidden killer pair 5,6 in R9C12 and R9C78 for R9, R9C78 contains one of 5,6 -> R9C12 must contain one of 5,6 -> no 6 in R8C1

16. R8C4 = 6 (hidden single in R8), R7C4 = 5, clean-up: no 2 in R8C7

17. 27(5) cage in N7 (step 12a) = {14679/24579}
17a. 2 of {24579} must be in R7C12 -> no 2 in R8C2
17b. Naked triple {145} in R8C237, locked for R8

18. 15(3) cage in N7 (step 13) = {168/258}
18a. 1 of {168} must be in R9C1 -> no 6 in R9C1
18b. 5,6 only in R9C2 -> R9C2 = {56}
18c. Naked triple {356} in R259C2, locked for C2
18d. 8 in N7 only in R89C1, locked for C1, clean-up: no 3 in R23C1

19. Naked pair {56} in R23C1, locked for C1 -> R5C12 = [35], R2C2 = 3, R2C3 = 8, R6C3 = 1, R3C23 = [14], R8C23 = [45], R8C7 = 1, R7C7 = 6, R4C12 = [47], R1C12 = [79], R6C12 = [28], R7C12 = [92], R89C1 = [81], R9C2 = 6, R89C5 = [98], R89C9 = [39], R89C6 = [23]

19. 25(5) cage in N3 contains 7 = {23479/23578/34567}
19a. 9 of {23479} must be in R3C8 (R123C7 cannot contain both of 4,9 which would clash with R5C7) -> no 9 in R23C7

20. R5C7 = 9 (hidden single in C7), R5C8 = 4

21. 4,7 in C7 only in R123C7 -> 25(5) cage in N3 (step 19) = {23479/34567}, no 8
21a. 2 of {23479} must be in R3C9 -> no 2 in R2C7 + R3C78

22. R4C7 = 8 (hidden single in C7), R3C6 = 9, R4C4 = 1, R5C9 = 1

23. Naked pair {14} in R12C6, locked for C6 and N2 -> R7C56 = [17], R5C6 = 8

24. R9C7 = 2 (hidden single in C7), R9C8 = 5

25. 25(3) cage in N3 (step 21) = {34567} (only remaining combination), locked for N3 -> R1C89 = [18], R2C89 = [92]

and the rest is naked singles.

A202 V0.85 started more easily than the V1 but then I really struggled to finish it. I couldn't see any way to make the final breakthrough using steps consistent with the SS score. Maybe someone else can find a way to continue from the position after my step 13 (or step 15) using simple steps.

I even took a break from this puzzle and did a similar number of steps on the V2.

Then I came back to V0.85 and found a nice short way to finish it but this is waaay OTT compared with the SS score.


Here is my walkthrough for A202 V0.85.

Prelims

a) R1C12 = {12}
b) R1C34 = {29/38/47/56}, no 1
c) R23C1 = {18/27/36/45}, no 9
d) R2C23 = {29/38/47/56}, no 1
e) R3C23 = {79}
f) R4C12 = {16/25/34}, no 7,8,9
g) R45C3 = {16/25/34}, no 7,8,9
h) R5C12 = {18/27/36/45}, no 9
i) R67C9 = {29/38/47/56}, no 1
j) R7C56 = {16/25/34}, no 7,8,9
k) R78C7 = {49/58/67}, no 1,2,3
l) R78C8 = {16/25/34}, no 7,8,9
m) R89C5 = {59/68}
n) R89C6 = {49/58/67}, no 1,2,3
o) R89C9 = {29/38/47/56}, no 1
p) R9C78 = {16/25/34}, no 7,8,9
q) 27(4) cage in N3 = {3789/4689/5679}, no 1,2
r) 18(5) cage in N3 = {12348/12357/12456}, no 9
s) Both 45(9) cages = {123456789}

Steps resulting from Prelims
1a. Naked pair {12} in R1C12, locked for R1 and N1, clean-up: no 9 in R1C34, no 7,8 in R23C1, no 9 in R2C23
1b. Naked pair {79} in R3C23, locked for R3 and N1, clean-up: no 4 in R1C4, no 4 in R2C23

2. 45 rule on N1 1 innie R1C3 = 6, R1C4 = 5, clean-up: no 3 in R23C1, no 5 in R2C23, no 1 in R45C3
2a. Naked pair {38} in R2C23, locked for R2
2b. Naked pair {45} in R23C1, locked for C1, clean-up: no 2,3 in R4C2, no 4,5 in R5C2

3. 45 rule on N7 1 innie R7C3 = 5, clean-up: no 2 in R45C3, no 6 in R6C9, no 2 in R7C56, no 8 in R8C7, no 2 in R8C8
3a. Naked pair {34} in R45C3, locked for C3 and N4 -> R2C23 = [38], clean-up: no 6 in R5C12
3b. Killer pair 1,2 in R4C12 and R5C12, locked for N4
3c. Naked pair {79} in R36C3, locked for C3
3d. Naked pair {12} in R89C3, locked for N7

4. R4C2 = 5 (hidden single in C2), R4C1 = 2, R1C12 = [12], clean-up: no 7 in R5C12
4a. R5C12 = [81]
4b. Naked triple {679} in R6C123, locked for R6 and 38(7) cage at R6C1, no 6,7,9 in R789C4, clean-up: no 2,4 in R7C9

5. 45 rule on N9 1 innie R7C9 = 7, R6C9 = 4, clean-up: no 6 in R78C7

6. 7 in N8 only in R89C6 = {67}, locked for C6 and N8, clean-up: no 1 in R7C56, no 8 in R89C5
6a. Naked pair {34} in R7C56, locked for R7 and N8, clean-up: no 9 in R8C7, no 3,4 in R8C8
6b. Naked pair {59} in R89C5, locked for C5
6c. Naked triple {128} in R789C4, locked for C4 -> R6C4 = 3

7. Naked triple {689} in R7C127, locked for R7, 6 also locked for N7, clean-up: no 1 in R8C8

8. 16(3) cage in N7 = {349} (only remaining combination) -> R9C2 = 4, R89C1 = {39}, locked for C1 and N7 -> R7C12 = [68], R8C2 = 7, R6C1 = 7, R6C23 = [69], R3C23 = [97], R89C6 = [67], R8C8 = 5, R7C8 = 2, R78C7 = [94], R7C4 = 1, R89C5 = [95], R89C1 = [39], R8C9 = 8, R9C9 = 3, R1C9 = 9, R89C4 = [28], R89C3 = [12]

9. 27(4) cage in N3 = {4689/5679} (cannot be {3789} because R2C9 only contains 5,6), no 3, 6 locked for R2 and N3
9a. 8 of {4689} must be in R1C8 -> no 4 in R1C8
9b. 7 of {5679} must be in R1C8 -> no 7 in R2C8
9c. Naked triple {456} in R2C189, locked for R2

10. 4 in R1 only in R1C56, locked for N2 -> R3C4 = 6
10a. 4 in C4 only in R45C4, locked for N5

11. 36(7) cage at R1C6 = {1236789} (doesn’t contain 5 so cannot contain 4), no 4
11a. 2 only in R23C6, locked for C6 and N2
11b. 6,7 only in R4C789, locked for R4 and N6

12. R1C5 = 4 (hidden single in R1), R7C56 = [34]

13. Naked pair {18} in R34C5, locked for C5 and 45(9) cage at R1C5
13a. R2C5 = 7, R6C5 = 2, R5C5 = 6, R2C4 = 9, R45C4 = [47], R45C3 = [34]

14. 1 in R2 only in R2C67, CPE no 1 in R4C7
14a. 1 in C9 only in R34C9, CPE no 1 in R3C6

15. 18(5) cage in N3 = {12348/12357}
15a. 4 of {12348} must be in R3C8 -> no 8 in R3C8

16. 27(4) cage in N3 (step 9) = {4689/5679} = [7965/8946]
16a. Killer triple 1,6,8 in R12C8 + R6C8 + R9C8, locked for C8

17. Consider placements for R1C8
R1C8 = 7 => R4C8 = 9 => R4C56 = {18}, locked for N5 => R6C6 = 5
R1C8 = 8 => R6C8 = 1 => no 1 in R6C6
-> no 1 in R6C6

18. 1 in R6 only in R6C78, locked for N6 -> R4C9 = 6

and the rest is naked singles.

I took a look at the techniques used by SudokuSolver and JSudoku:

Hi Andrew - the way I would proceed from your diagrammed position is:

If r1c8 = 8 then you get 2 1's in nonet 6.

So r1c8 = 7 and that solves the puzzle.

Cheers - Frank

In this position there is an X-Wing on 1 ◄ Select to see the digit the X-Wing is on.
There is also a Swordfish on the same digit, yielding the exact same eliminations as the X-Wing.

  EDIT

  EDIT

Perhaps Sudoku-Solver's X-Cycle Simple 2 is a Y-Wing?

In my ratings explained I rate Y-Wing as a Super Hard technique and all Chains as an Ultra Hard technique.

These puzzles are very different to 99% of killers posted here since they have a hard, interesting ending after many easy placements. Yet for me, still definitely killers, not vanillas, since no X-wings, Y-wings or Swordfish (damn..love all them!! Thanks for showing them Børge [edited after next post].)

(edit2: I'm never opposed to using those techniques and love finding them. Unfortunately, I didn't use any of them. Instead, for both the v0.85 and v1 I used quite tricky killer steps. I would have been very happy to have not found those shortcuts and have found the wings instead. Did the V1 the same way as Andrew (his step 13). Very Assassin step. Took me a long while to find too with lots more little eliminations in other areas first.

V0.85 came out a lot quicker. Closest to Frank's way. BTW, the ALT 5 SS score is 1.00 ◄ Select [edit: Note, in next release of SS with different routine weightings than current version as explained here]
Still completely stuck on the V2.

Cheers
Ed

Why not?
Back in the 70's and 80's when I studied IT, Math, Physics and Statistic we were often required to use only certain techniques to solve a problem. Really stupid if you ask me. Now in everyday life I use whatever means and techniques I know and master to get a problem solved the best possible way using as little time as possible. That's what counts and makes the bucks. No point in spending 40 hours to solve a problem using only techniques from set A when you can solve it in 25 hours using different or additional techniques.

You are wrong! it is 0.10 lower!

Very happy about that!
Wonder how Joe Casey, our pen and paper solver in chief is doing?