Solution to the weekly extreme Str8ts puzzle #53 from www.str8ts.com

1. Weekly Extreme Str8ts Puzzle #53 June 26 – July 2, 2011www.str8ts.com Solution bySlowThinker

2. Start position Extreme Str8ts #53 again has mostly large compartments, which indicates that we can make good use of Setti’s rule.

3. Solving… C3=4h G8=5d C2=5h C1=3

4. Solving… F56 contains the hidden pair 89  we can remove all other candidates there. E4=5p G4=3p

5. Solving… H2=3s A7=3s H7=5s

6. Setti’s rule on 7 Checking the number 7, we find that it must occur in every row  it must occur in every column too  it is in column 1  range of BCDEF1 is 34567  E1=4S7

7. Solving… E9=3 F2=1s

8. Setti’s & X-Wing Checking Setti’s rule on 2 we find that 2 must appear in row A, as 2 appears in 7 columns  A4=8S2 We therefore have an X-Wing on 2 at AB35 (marked blue), which removes the 2s from the yellow cells  G3=1x

9. Solving… From here on the puzzle is straight forward. B4=9 G5=4 G2=2 J2=4 J4=6 F4=4

10. Solving… F8=2 H8=4 H9=6 G9=7 D9=4 G7=6

11. Solving… F7=7 J7=2 J6=1 H6=2 H3=8 H5=1

12. Solving… F1=6 J5=7c C8=9p C5=6 C6=7

13. Solving… E5=8 E6=6 E3=7 F5=9 F6=8

14. Solving… A3=2p B3=6 D3=9 B8=7 A8=6 A2=7

15. Solving… A5=5 A6=4 D2=6 B2=8 B1=5

16. Solving… D1=7 B6=3 B5=2 D6=5 D5=3

17. Done As anticipated, we were able to put Setti’s rule to good use. Once the X-Wing on 2 was applied, the puzzle was easy.

18. Glossary Letters appended to steps indicate the last strategy used, just before filling in a field: No letter … number was last candidate in field s … single (last) candidate for that number in compartment c … compartment range check d … stranded (unreachable/impossible) digits removed h … high/low range check across compartments p/t/q … naked pair / naked triple / naked quadruple ph/th/qh … hidden pair / hidden triple / hidden quadruple x … X-wing (2 rows / 2 columns) w … Swordfish (3 rows / 3 columns) j … Jellyfish (4 rows / 4 columns) L … large gap field Sx … Setti’s rule (count the numbers rule) – ‘x’ is the analysed number u … unique rectangle y … Y-Wing or XY-chains

19. Weekly Extreme Str8ts Puzzle #53www.str8ts.com Solution by SlowThinker Note: there are other (maybe easier) ways to solve this puzzle.