## Hard** 6/8/17

Post puzzles for others to solve here.

### Hard** 6/8/17

Code: Select all
`  *-----------*  |.1.|..5|...|  |...|96.|...|  |..5|...|432|  |---+---+---|  |..8|2..|..5|  |.2.|.1.|.8.|  |.4.|...|..3|  |---+---+---|  |2..|5.6|...|  |..6|...|54.|  |1..|.34|8..|  *-----------*`

The two *s mean the solution uses one of these: Xwing, Ywing or XYZwing.
nedBlake
2018 Supporter

Posts: 31
Joined: 08 May 2016

### Re: Hard** 6/8/17

Singles plus one pointing pair brings this one to BUG+1. Then singles.
Steve

SteveG48
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Posts: 2374
Joined: 08 November 2013
Location: Orlando, Florida

### Re: Hard** 6/8/17

What Steve said about BUG's was correct, but BUG's is a fairly esoteric topic that newspapers, books and many solving sites generally don't talk about.

So here is a solution ignoring BUGs: After a basic markoff, and a pointing pair of 7's in r78c9 (as Steve said), which removes two 7's in r12c9 you get to here :

Code: Select all
`*--------------------------------------------------------------*|a78    1     3      | 4     2     5      | 79    6    b89     || 4     78    2      | 9     6     3      | 17    5     18     || 6     9     5      | 8     7     1      | 4     3     2      ||--------------------+--------------------+--------------------|| 3     6     8      | 2     4     7      | 19    19    5      || 5     2     7      | 3     1     9      | 6     8     4      || 9     4     1      | 6     5     8      | 2     7     3      ||--------------------+--------------------+--------------------|| 2     78    4      | 5     89    6      | 3     19    179    || 8-7   3     6      | 1     89    2      | 5     4    c79     || 1     5     9      | 7     3     4      | 8     2     6      |*--------------------------------------------------------------*`

The XY Wing (we call a Y wing an XY wing here) cells are a, b and c, which removes the 7 in r8c1 and effectively solves the puzzle, so the ** rating is correct.

I assume you know how XY wings work. If you don't, just let me know and I'll explain in more detail.

Leren
Leren

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Joined: 03 June 2012