dailysudoku.com

[cgordon]

The Hard sudokus are rarely discussed in the forums because they involve no advanced techniques. But often they are quite challenging in their own way. I thought today’s was a good one. There are no 9’s for a start.

[crunched]

I don't understand how people solve any of these puzzles (except maybe the "easy" ones) in just a matter of minutes. Actually, it seems like the VH puzzles are usually easier than the hard--or oftentimes even medium puzzles to get through a lot of the basics.

This hard puzzle took me a LONG time to resolve. I had to use an x-wing (or did I use 2 x-wings altogether? I can't entirely remember now) to finally crack the puzzle.

Did anyone actually solve this puzzle without using a wing?

[sdq_pete]

I was wondering the same. It took me quite a time and I took recourse to a number of advanced techniques (W-wing, X-wing, XY-wing). Whether any of them were really necessary or not I don't know, but I seemed to need them to progress.

Peter

[Marty R.]

[cgordon]

I believe by definition, the Hards should not require wings. I used basic stuff for this one but it took me a while. Looking at the 9's in the middle box finally did it.

[nataraj]

I did the puzzle just now on paper.

No wings. Definitely.

First breakthru when I spotted the naked pairs 19 and 68 in col 2, then NP 27 box 1/row 2 and naked triple 369 in col 6 which solved 2 and 4 in box 5. No major obstacles after that.

[nataraj]

And to add a few words about timing - quote: "a matter of minutes":

this puzzle took me 21 minutes.
that is rather long for a "hard", but not excessive.
"hard" from this site or in my local paper, and "fiendish" in the London Times always can be solved by basic means and usually take me between 15 and 20 minutes.

When I reach 20 minutes for a "hard" and I am still stuck, I then decide that I am suffering from a mental block (my brain refuses to see the clues), I let it rest for like half a day and when I come back the puzzle solves itself

When I solve a puzzle in under 14 minutes I am disappointed, because I feel that it was too easy .

I cannot remember ever having solved a puzzle in less than 10 minutes (I don't do "easy" or "medium"). The initial phase ("sweeping the floors") alone takes a few minutes.

Of course, the online version, with auto-sweep on, allows much shorter times. But then, what is the point? I am not trying to prove how fast I can write or how fast I can click.

[keith]

This one is quite simple, once you see it! (But, yes, it took me quite a while.)

R7C6 is <5>, R3C1 is <8>.

The <2> and <7> in C2 force a pair <27> in B1 in R2.

Look at C6. R1C6 is <7>, and the <9> in B5 lies in C6.

Which solves R6C4 as <2>. All that remains is to recognize that there is a pair <19> in C2 and in R2.

Keith

[Victor]

Should do this more often! Like the good old days, when we didn't use candidate numbers, and some people even did puzzles without putting a single mark on the paper. I used to like Sudoku-san for puzzles like this - basics + X-wings, but I noticed recently that the site seems to have bit the dust, which is a pity.

[keith]

[cgordon]

As an interesting comparison, I did today’s Hard (31 Mar) in no time at all using the auto-sweep. Unlike Nataraj I have no compunctions about using auto-sweep - and would never, like Keith, attempt a puzzle without pencil marks. It’s like the old Masters - Rembrandt, Mike Angelo etc: they only did the good bits and had someone else prepare the canvas. Although it could also be my natural laziness.

[nataraj]

[crunched]

[quote="nataraj"]

[ravel]

[Victor]

Thanks Keith. I haven't previously tried this site. Nice paper-and-pencil puzzle.