3. Caution! There is severe testing/guessing ahead. You cannot solve the puzzle without it, which does take some of the fun away for some people. If you don’t like to test/guess, solve the puzzle with E8=7 added. This puzzle will still be very challenging, but can be solved without further guessing. Have fun! 7 Solution for E8=7 isshownatthe end.
7. Setti‘srule on 5 Checking the number 5 we find that there must be a 5 in every column. Therefore there must be a 5 in every row G2=5
8. G2=5S5, C2=6, B1=6s There is a hidden pair 56 in the green area other candidates can be removed.
9. X-Wing on 5 The blue X-Wing on 5, removes the 5s in the green fields.
10. Unique rectangle & Setti on 6 Setti‘s rule on 6: every column has a 6 every row must have a 6 F8=479 Blue rectangle: F56 cannot be 89 9s can be removed in F56. This works because the only 8s are in F56 too, e.g. one cannot apply this to row E.
11. An unorthodox chain 3 4 G1=3 G1=4 Looking at the lower left, examining possible values for G1: G1=3 H1:-3, G3=4 J3:-4 G1=4 HJ1=23. Together with HJ4 we can apply the unique rectangle rule, which forces J4=4 H4=3 J3:-4, H1:-3 In both cases, 3 gets removed from H1 and 4 gets removed from J3 we can remove both candidates.
12. Anothercombination If B5 (green) is either 8 or 9, then we have the naked pair 89 together with G5 (blue) that removes 89 from the orange fields. What happens if B5=4? B5=4 B4=8 (only other 8 in row) C4=79 C5=8 With C5=8 we get G5=9 and again 89 is removed from the orange fields. We can remove 89 from EFH5and 9 from C5 in either case. 4
14. Variation by Walter: Setti‘srule on 8 Column 7 doesn‘t have an 8, column 3 and the rows C and F may have no 8. Either row C or row F doesn‘t have an 8, or both have no 8, in which case column 3 must not have an 8 either. Testing row F: If there’s an 8 in row F no 8 in row C. If there’s no 8 in row F F3=2 no 8 in column 3 (range!) two columns with no 8 no 8 in row C. There’s never an 8 in row C C45=45!
22. More combinationswithSetti Ideaby Walter Lookingat F5..9 again: Ifthereisno 8 in F59, F5..9=2..7. Ifthereis an 8 in F59 E3=8 (becauseofSetti‘srule on 8) J3=7 J8=9 F8=47 F5..9=2..8.In bothcases, F5..9 contains a 4! F8=47 (9 is out ofrange)
23. Setti‘srule on 4 Wenowknowthateveryrowcontains a 4 everycolumn must contain a 4 aswell H1=2
24. H1=2S4, H4=3 F2 cannot be 3, because F2=3 F3=2 F5..9 contains an 8 E3=8 (Setti) which contradicts F3=2 (range!) [idea by Walter]
25. Testing F3=3 Ideaby Walter If F3=3 F2=2c, F6=8h E3=8S8, E2=139, F5=67 E5=3s no 2 left in row E F3 cannotbe3. FromthereitfollowsthatF2=19, F3=28 EJ3 : -28 (large gap pair F3), F6!=8 (S8), J2=23p J3=7s!
27. E3=9u The blue fields form a Swordfish on 8 and on 9, the one on 9 is disturbed by E3. But if E3!= 9 E46=89 and we do not get a unique result, because the 8s and 9s in BEG456 could be swapped in order to get a unique solution E3=9
28. Variation by Walter Testing F5=2 F5=2 F7=3s, F8=4c B8=5, A7=5 no cell left for 6 in column 7. We therefore know that F5!=2 and F5..9=34567. Setti`srule on 7 Now 7s are confirmed everywhere except in column 7 and row A. Both have a 7 D7=1. No 7 in row A/column 7 H7=19, H5=57 X-Wing on 1 at AE58 neither E7 nor A7 can be 1 D7=1. So, in both cases there is no 3 in row D according to Setti`s rule no 3 in column 3 G3=4, F3=8, E3=9. From there the puzzle solves easily.
31. X-Wings on 3 and 1 The blue (horizontal) X-Wing on 3 (EF57) removesthe 3 from D7 D7=1 The orange (vertical) X-Wing on 1 makes 1 a surecandidate in A4..9 7 isremovedfrom A..9, A4..9=123456
32. D7=1x Setti‘s rule on 7: row A doesn‘t contain a 7 at least one column doesn‘t contain a 7 either H7=9 and eight columns contain a 7 row F must contain a 7 A5=2s
38. Variation: E8=7 7 In the following, just the most important points are shown, when trying to solve this variation of the puzzle.
39. Setti‘srule on 5 and X-Wing Setti‘s rule: there‘s a 5 in every column, therefore also in each row G2=5 This then gives an X-Wing on 5 (marked blue,) and a hidden pair J56=56
40. Setti‘srule on 6 There‘s a 6 in each column, therefore a 6 in each row F8=4. Next important steps are the resulting singles D4=7, A4=6, J3=7 and F6=7.
41. Large gap pair & Swordfish F3=28 is a large gap pair, which removes 2 and 8 from E3. With that we have a Swordfish on 8 that results in C4=5.After that the puzzle solves itself.
42. 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
43. Weekly Extreme Str8ts Puzzle #45www.str8ts.com Solution by SlowThinker & Walterwith a variation by Jan Note: there are other (maybe easier) ways to solve this puzzle.