| This Friday puzzle... (Friday, 21st February 2014) |
MondSemmel
Kwon-Tom Obsessive
Puzzles: 6159
Best Total: 7m 47s | Posted - 2014.02.21 21:29:13
...was impressively hard. Wow. The hardest in my recent memory. I tried a ton of explorations and they all ended in separately closed loops after what felt like an eternity  .
Good job, foilman! Though I'm glad puzzles this hard are rare... |
Zyntax
Kwon-Tom Obsessive
Puzzles: 6534
Best Total: 13m 6s | Posted - 2014.02.22 02:05:26
Wow, I must have got lucky then!
So far, no Friday puzzle has been harder to me than the July 13, 2012 one. |
Tilps
Kwon-Tom Obsessive
Puzzles: 6720
Best Total: 18m 37s | Posted - 2014.02.22 04:50:16
This puzzle was interesting to me, I got a pretty good time it seems, but only by luck. Not the luck of a good trial, but instead the luck of guessing how to continue a trial correctly 3 times in a row...
So I decided to dig out my solver and take a closer look at interesting things it found to see if I could find what would have been an actual lucky trial - or maybe just something interesting.
So far I've found I missed some simple local contradictions and counting in the bottom right (solving them a much harder way when I was doing the puzzle), and the 3 1 2 L shape on a virtual edge pattern in the top middle left.
With those done the trial of a cross on the left most edge of the 3 in the middle of the left edge fails pretty easily giving a line which introduced me to another pattern I've not considered before, 2 diagonal feeders into the cell at the end of a pair of 3's must feed into each other, because they can't feed into the 3. So that seemingly insignificant line actually gives a bit more.
Next trial is the edge below the bottom right corner of that 3 where a line leads to a pretty quick contradiction. What I am failing to work out is how that x then leads to quite a significant series of simple logic without trials.
So from:
my solver tells me I can derive:
which finishes off the bottom right hand corner of the puzzle.
The easiest way I've come up with to show that is that it is a quick common consequence of trying both options for the bottom edge of the 3, but maybe someone else can give a better explanation? (My solver long ago passed my levels of comprehension, so I'm not even vaguely sure what strategies it considered here  ) |
Tilps
Kwon-Tom Obsessive
Puzzles: 6720
Best Total: 18m 37s | Posted - 2014.02.22 05:26:08
A few more small (but not entirely obvious) trials later... gets the puzzle like this:
From here the 'lucky trial' is on the 3 just above the middle like so:
I didn't think this went very far, but it is the second last edge on the same row as the 3 to fill in, and counting causes trivial cascade to the end.
Backtracking a bit and doing some more investigation, seems that that 3 is the key location of the puzzle. |
arbor8
Kwon-Tom Obsessive
Puzzles: 5584
Best Total: 13m 24s | Posted - 2014.02.22 12:47:55
I found the 3 in (1,5) to be critical for my solving.(SW corner =(1,1)
At first,I wrongly concluded that it opens up in NE, but it leads in multiple solutions in the lower left corner
Opening up in SW,looks like this:
The July13 2012 puzzle was much harder than this one |
MondSemmel
Kwon-Tom Obsessive
Puzzles: 6159
Best Total: 7m 47s | Posted - 2014.02.22 13:43:47
By "hardest in my recent memory", I meant in the last weeks or maybe months, certainly not 1.5 years . |
Zyntax
Kwon-Tom Obsessive
Puzzles: 6534
Best Total: 13m 6s | Posted - 2014.02.23 00:32:36
lol Yeah I know, but that puzzle was so hard for a Friday puzzle, I remember making a post about it so it was easy to dig up the date. |
