This document provides the solution to the Weekly Extreme Str8ts Puzzle #50 by SlowThinker. It summarizes the key steps taken, which included using Setti's rule to eliminate candidates, cross-compartment analysis to remove digits, and an X-wing technique. Cross-compartment checks and strategies that analyze multiple compartments at once are particularly useful for puzzles with three compartments in a row or column.

1. Weekly Extreme Str8ts Puzzle #50
June 5 – June 11, 2011
www.str8ts.com
Solution by
SlowThinker

2. Start position
I designed Extreme
Str8ts #50. Of the
puzzles I design, about
1 in 7 are difficult
enough to get
str8ts.com’s 5-star
difficulty rating.
Solving
A8=9h
J8=8

3. Solving…
A6=7d
B6=8d
Because of A7 now being
346 we can remove 6 from
B7.
B4=6s
B5=5s

4. Removing
candidates…
Because of
ABH7=3467 (blue) we
can remove 4 and 6
(and thus 7) from DE7
(green.)
Cross-compartment
analysis like this is a
useful technique in
Str8ts.

5. Setti on 8
Checking Setti on 8 we
find that all rows
except row G contain
an 8. Column 7
doesn’t contain an 8
either, so column 2
must contain an 8, i.e.
we can remove 123
from CDEFG2 
D2=8S8
G2=4S8
D1=9c

6. Solving…
F8=2h
F9=1
C8=3d
C9=2

7. Solving…
G6=2p
G5=1c
D7=2s
E7=1

8. X-Wing
There’s an X-Wing on
1 at HJ46 (blue) that
removes the 1s from
the green fields 
A1=1s
A2=3
A7=6
B7=7c

9. Solving…
B3=9
H7=4
H5=3
D5=4
D4=5

10. Solving…
A4=4
A9=5
D8=6
D6=3

11. Solving…
G9=6
G8=5
E8=4
H9=8
H1=6

12. Solving…
E9=9
J5=9s
C1=5p
C2=6

13. Solving…
F3=3s
E3=2c
H3=5d
J3=6c
H6=1

14. Solving…
H4=2
J4=1
J2=2
J6=4
J9=3
J1=7

15. Solving…
B9=4
B1=2
E1=8
F1=4
F6=5

16. Solving…
F2=7
E2=5
F4=8
C4=7
C5=8
E5=7
E6=5

17. Done
Setti’s rule was
essential in solving
this puzzle.
Cross-compartment
checks are useful too.
They are an effective
strategy, especially
when there are three
compartments in a
single row or column.

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 #50
www.str8ts.com
Solution by SlowThinker
Note: there are other (maybe easier) ways to solve this puzzle.