Author Topic: Sudoku  (Read 6760 times)

ElyDave

  • Royal and Ancient Polar Bear Society member 263583
Re: Sudoku
« Reply #25 on: 29 February, 2016, 06:29:48 am »
anyone else come across a non-unique solution?

I had one with 4 spaces left, two pairs of numbers say 3s and 4s which I could put in two combinations without affecting the validity of the answer.

Never seen that again.
“Procrastination is the thief of time, collar him.” –Charles Dickens

arabella

  • no se porque yo no lo se
Re: Sudoku
« Reply #26 on: 01 March, 2016, 06:44:22 pm »
yes, but I couldn't say when.  a set of pairs that could go either way around.
usually if I have one I then resort to arithmetic and find there is in fact only one solution - but arithmetic ony an option if you are doing killer sudoku, which is why i prefer it to the normal kind - the normal sudoku you could substitite shapes for numbers and it'll still work.
(circle, oval, triangle, square, oblong, lozenge, star, pentagon, hexagon, for example)
In the dark, all views are the same.

Riggers

  • Mine's a pipe, er… pint!
Re: Sudoku
« Reply #27 on: 03 March, 2016, 01:23:43 pm »
I can't quite believe what I'm reading.
Certainly never seen cycling south of Sussex

Wowbagger

  • Sylph
    • Musings of a Gentleman Cyclist
Re: Sudoku
« Reply #28 on: 01 May, 2016, 08:31:01 pm »
Tricky one today.

http://www.killersudokuonline.com/play.html?puzzle=D2kkas63774&year=2016

It seemed to be very easy initially, and I completed about half the puzzle in no time, but I really struggled with the second half.
Bach without a doubt.

Wowbagger

  • Sylph
    • Musings of a Gentleman Cyclist
Re: Sudoku
« Reply #29 on: 02 June, 2020, 03:16:15 pm »
Since the lockdown began, I have resumed solving the daily Killer Sudoku.

The website I frequent issues a number of puzzles each day. Their Monday puzzle is reckoned to be the easiest, and they gradually increase in difficulty through the week, Sunday's being the hardest. I don't normally have much trouble, although some of the tougher ones can have me racking my brains.

Today's was labelled "Easy" but I thought it was a right git.

https://www.killersudokuonline.com/play.html?puzzle=D2kmxyp5267&year=2020

Some chap called Andrew Stuart has written a rather good Sudoku Solver which I occasionally use to give me some hints. It's not that uncommon, with the harder puzzles, for his solver to run out of techniques before I do.

https://www.sudokuwiki.org/killersudoku.htm
Bach without a doubt.

SoreTween

  • Most of me survived the Pennine Bridleway.
Re: Sudoku
« Reply #30 on: 05 June, 2020, 09:30:53 pm »
I'm badly out of practice but sodding hell! I must be over an hour in and I've not found my first solid number yet.  The Outrageous linked in reply #8 was a doddle compared to this Easy.

(don't like the 'check' feature on that site, it's too easy to accidentally cheat)

2020 targets: None
There is only one infinite resource in this universe; human stupidity.

mattc

  • n.b. have grown beard since photo taken
    • Didcot Audaxes
Re: Sudoku
« Reply #31 on: 05 June, 2020, 09:59:51 pm »
Since the lockdown began, I have resumed solving the daily Killer Sudoku.

The website I frequent issues a number of puzzles each day. Their Monday puzzle is reckoned to be the easiest, and they gradually increase in difficulty through the week, Sunday's being the hardest. I don't normally have much trouble, although some of the tougher ones can have me racking my brains.

Today's was labelled "Easy" but I thought it was a right git.

https://www.killersudokuonline.com/play.html?puzzle=D2kmxyp5267&year=2020
Nope, beats me! (I can do all the Times ones with a biro, any grade, although the hardest sometimes take me quite a long time to get going. I always have to scribble some notes somewhere. If I printed this out I could persevere for a bit longer, but I can't promise I'd get started. I don't really enjoy spending 30 minutes getting started; it's the Middle Game that's usually most fun.)

I would not call it "Easy".
Has never ridden RAAM
---------
No.11  Because of the great host of those who dislike the least appearance of "swank " when they travel the roads and lanes. - From Kuklos' 39 Articles

SoreTween

  • Most of me survived the Pennine Bridleway.
Re: Sudoku
« Reply #32 on: 10 June, 2020, 09:35:00 am »
Woot! Got there eventually.  Lack of practice wasn't a factor, that's a harder puzzle than I've ever persisted with before.  I did use the solver for two hints, both things I should have spotted (7 in row A early on, can't recall the other).

Stepping right through with the solver afterwards I find three things:
1) It makes a lot of use of innies & outies.  I must learn to spot those, I didn't know that trick.
2) The solver only used rules down to Killer combos (hard).  I used those as my primary weapon.
3) That means I'm not even at the stage of using all the 'tough' strategies so I have a great deal left to learn/figure out.

Yesterday' 'easy', is.
2020 targets: None
There is only one infinite resource in this universe; human stupidity.

Wowbagger

  • Sylph
    • Musings of a Gentleman Cyclist
Re: Sudoku
« Reply #33 on: 10 June, 2020, 11:00:39 pm »
The annoying thing about "innies & outies" is that you sometimes have to revisit them multiple times, each time narrowing down the possible range of numbers until you have eliminated all but the right answer(s). When you have to add up 4 rows or columns to find the difference between what is stated in the cages and 225, it is areal  test for your mental arithmetic. But I reckon that these are a good way to keep the brain active and (hopefully) keep the dementia fairy at bay.

It's got to the point that I can solve most puzzles in well under an hour now.
Bach without a doubt.

SoreTween

  • Most of me survived the Pennine Bridleway.
Re: Sudoku
« Reply #34 on: 13 June, 2020, 11:15:30 am »
Have you looked at this week's Mind Bender?  I'm stuck so I put it into the solver.  I'm quite pleased that it too is stuck having made just one more elimination than me.

I can't see a cell that is key enough to be worth going down the guess route.

Set this cookie to go straight to that point:
(click to show/hide)
2020 targets: None
There is only one infinite resource in this universe; human stupidity.

Wowbagger

  • Sylph
    • Musings of a Gentleman Cyclist
Re: Sudoku
« Reply #35 on: 13 June, 2020, 11:30:02 am »
I did that a couple of days ago but my machine seems to have forgotten it.

I'll have another go. I did today's https://www.killersudokuonline.com/play.html?puzzle=D368c7k5278&year=2020 in about 45 minutes.

PS I don't know how to set a cookie...
Bach without a doubt.

Wowbagger

  • Sylph
    • Musings of a Gentleman Cyclist
Re: Sudoku
« Reply #36 on: 13 June, 2020, 01:25:41 pm »


Progress...
Bach without a doubt.

Wowbagger

  • Sylph
    • Musings of a Gentleman Cyclist
Re: Sudoku
« Reply #37 on: 13 June, 2020, 01:28:36 pm »
Bach without a doubt.

Wowbagger

  • Sylph
    • Musings of a Gentleman Cyclist
Re: Sudoku
« Reply #38 on: 13 June, 2020, 02:18:46 pm »
I got there in the end.

I think the trickiest bit initially was realising the limited number of possibilities in the top row, once you've got the 789 triple for the 24-cage starting on A1. All the rest must be one of 123456 and the cage of 6 cells totalling 39 must be made of 456789. That then limits the two squares A6 & A7 to 4, 5 and 6.

Later on there was the elimination of 7 from A1 and J1. That was dependent on realising that C1 is valued at 6. 6 aded to the 18 in the cage starting at E1 meant that neither of those squares could be 7.
Bach without a doubt.

SoreTween

  • Most of me survived the Pennine Bridleway.
Re: Sudoku
« Reply #39 on: 15 June, 2020, 08:59:47 pm »
I got there in the end.
I'm no further forward.

I think the trickiest bit initially was realising the limited number of possibilities in the top row, once you've got the 789 triple for the 24-cage starting on A1. All the rest must be one of 123456 and the cage of 6 cells totalling 39 must be made of 456789. That then limits the two squares A6 & A7 to 4, 5 and 6.
Got all that very quickly.  Getting from there to the reductions in your first screenshot has be stumped.  Still working through the available combinations.
2020 targets: None
There is only one infinite resource in this universe; human stupidity.

Wowbagger

  • Sylph
    • Musings of a Gentleman Cyclist
Re: Sudoku
« Reply #40 on: 16 June, 2020, 10:29:07 am »
Can you post a screenshot of where you are up to? I can't recall my thought processes.

I've reopened the puzzle and loaded it as far as the "Sudoku Solver" takes you before it runs out of ideas.
Bach without a doubt.

SoreTween

  • Most of me survived the Pennine Bridleway.
Re: Sudoku
« Reply #41 on: 16 June, 2020, 01:02:26 pm »
One step forward, 5&6 placed in B4, B5 & A7.



I've not fully investigated the implications of that step yet.  Not having much time at the moment but that seems to help.  I keep seeing things in the first couple of minutes I'd not spotted in earlier long sessions (I have 3 on the go at the moment)

[ETA]Ah yes, the 4 within the 39 group has been pushed inside square 2, that's the next step.  Investigating....
2020 targets: None
There is only one infinite resource in this universe; human stupidity.

Wowbagger

  • Sylph
    • Musings of a Gentleman Cyclist
Re: Sudoku
« Reply #42 on: 16 June, 2020, 01:44:36 pm »
(click to show/hide)
Bach without a doubt.

SoreTween

  • Most of me survived the Pennine Bridleway.
Re: Sudoku
« Reply #43 on: 16 June, 2020, 03:46:35 pm »
(click to show/hide)
2020 targets: None
There is only one infinite resource in this universe; human stupidity.

Wowbagger

  • Sylph
    • Musings of a Gentleman Cyclist
Re: Sudoku
« Reply #44 on: 16 June, 2020, 04:00:18 pm »
You can also make progress with the innies/outies in Column 7.

That, in turn, has implications for the 3 cells total value 15 in the bottom RH block , and of course the bottom row of the RH middle block..
Bach without a doubt.

Wowbagger

  • Sylph
    • Musings of a Gentleman Cyclist
Re: Sudoku
« Reply #45 on: 18 July, 2020, 11:08:17 pm »
https://www.killersudokuonline.com/play.html?puzzle=D37shr35313&year=2020

That was an utter sod.

Normally, even for supposedly "hard" puzzles, a point comes when it just falls into place. That didn't for me. I was battering it for a couple of hours, I reckon.
Bach without a doubt.

Re: Sudoku
« Reply #46 on: 19 July, 2020, 01:47:28 pm »
Yesterday's Guardian killer (https://www.theguardian.com/lifeandstyle/2020/jul/18/killer-sudoku-719) has overlapping inner shapes. Is that a thing, or a mistake? I failed at the point where I got to filling in that area, and can't be arsed to backtrack as I can't see that I went wrong anywhere.
Quote from: tiermat
that's not science, it's semantics.

Wowbagger

  • Sylph
    • Musings of a Gentleman Cyclist
Re: Sudoku
« Reply #47 on: 19 July, 2020, 02:26:29 pm »
A quick count-up gave a grand total of 405 (9*45), so I think that must have been a mistake. Otherwise, that extra square would have been counted twice and the total would have ben >405.
Bach without a doubt.

Wowbagger

  • Sylph
    • Musings of a Gentleman Cyclist
Re: Sudoku
« Reply #48 on: 18 December, 2020, 03:22:04 pm »
https://www.killersudokuonline.com/play.html?puzzle=D3sk7v25465&year=2020

Moderate, allegedly. Took me ages. Very hard to unpick, right to the end.
Bach without a doubt.

JennyB

  • Old enough to know better
Re: Sudoku
« Reply #49 on: 28 December, 2020, 05:45:18 pm »
I'm addicted to Simon Anthony's solves on Cracking the Cryptic; elegant handcrafted Sudoku variants and other puzzles solved in  real time with a running commentary of his reasoning.

Here's one that I'm particularly proud of having worked out for myself - eventually: The Miracle Sudoku

Jennifer - Walker of hills