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Str8ts Weekly Extreme #59 - Solution

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Solution to the weekly extreme Str8ts puzzle #59 from www.str8ts.com

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Str8ts Weekly Extreme #59 - Solution

  1. 1. Weekly Extreme Str8ts Puzzle #59 August 7 – August 13, 2011www.str8ts.com<br />Solution & puzzle bySlowThinker<br />
  2. 2. Start position<br />Extreme Str8ts #59 was designed by me, and it has a peculiar feature that is the central focus of this puzzle.<br />
  3. 3. Solving…<br />Removing stranded digits eliminates many candidates at this point…<br />A5=4d<br />C5=3c <br />A4=5<br />C4=2<br />
  4. 4. Solving…<br />C7=1s<br />A2=89, because of C..G2, therefore C..G2 cannot contain a 9 as it would leave A2 without candidates.<br />Also, 1 is a stranded digit in D3.<br />
  5. 5. Solving…<br />G3=1s<br />G6=2s<br />F7=2s<br />A2=9p<br />… and because of the pair 78 in CF2, we can remove 3 as candidate from DE2.<br />
  6. 6. Solving…<br />Because of E2=46 we can remove 2 from E3 (stranded) and 9 from E13 (range check.)<br />D3=2s<br />D2=4c<br />D4=3<br />D5=5<br />
  7. 7. Solving…<br />E2=6<br />B4=4<br />B3=3p<br />G1=6s<br />D9=6s<br />
  8. 8. Setti’s rule on 6<br />There are 8 rows that have a 6, so 8 columns must contain a 6 too  GHJ5 contains a 6.<br />Note that E5 cannot be 5 or 8 due to E123 and E789.<br />
  9. 9. Unique solution constraint<br />This is the key point of this puzzle: looking at E5 we find that of all fields that influence E5, only E789 affects E5. Thus if E789 would notcontain a 9, E5 could be either 1 or 9 which would violate the unique solution constraint <br />E789=789u<br />E5=1u<br />
  10. 10. Solving…<br />E2=4h<br />E3=5h<br />F8=5s<br />B6=6h<br />B7=5<br />
  11. 11. Solving…<br />Due to H1, H3..7 cannot end at 9, as this would leave H1 without candidates <br />H4=7h<br />G4=9<br />C1=9p<br />C9=5p<br />
  12. 12. Solving…<br />H1=8<br />F1=7<br />F2=8<br />F3=9<br />C2=7<br />C6=8<br />
  13. 13. Solving…<br />A6=7<br />H3=6<br />H7=4<br />H5=5<br />H6=3<br />F6=4<br />
  14. 14. Solving…<br />A3=8<br />A7=6<br />J3=7<br />J5=6<br />J6=5<br />J7=9<br />
  15. 15. Solving…<br />J8=4c<br />G5=7c<br />G8=8<br />D8=7<br />D7=8<br />F9=3<br />
  16. 16. Solving…<br />E7=7<br />E8=9<br />E9=8<br />G9=4<br />B9=7c<br />
  17. 17. Solution<br />This puzzle showed that the unique solution constraint not only comes in form of a unique rectangle, but also in terms of compartments influencing each other.<br />For more information see my strategy slides.<br />
  18. 18. Glossary<br />Letters appended to steps indicate the last strategy used, just before filling in a field:<br />No letter … number was last candidate in field<br />s … single (last) candidate for that number in compartment<br />c … compartment range check<br />d … stranded (unreachable/impossible) digits removed<br />h … high/low range check across compartments<br />p/t/q … naked pair / naked triple / naked quadruple<br />ph/th/qh … hidden pair / hidden triple / hidden quadruple<br />x … X-wing (2 rows / 2 columns)<br />w … Swordfish (3 rows / 3 columns)<br />j … Jellyfish (4 rows / 4 columns)<br />L … large gap field<br />Sx … Setti’s rule (count the numbers rule) – ‘x’ is the analysed number<br />u … unique rectangle<br />y … Y-Wing or XY-chains<br />
  19. 19. Weekly Extreme Str8ts Puzzle #59www.str8ts.com<br />Solution by SlowThinker<br />Note: there are other (maybe easier) ways to solve this puzzle.<br />View & download my strategy slides from:<br />http://slideshare.net/SlowThinker/str8ts-basic-and-advanced-strategies<br />or from Google Docs:<br />http://is.gd/slowthinker_str8ts_strategy<br />

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