## Stuck

Post the puzzle or solving technique that's causing you trouble and someone will help

### Stuck

Could anybody give me help in identifying the next step? I checked naked 2, 3 and 4, but I got stuck. I have the answer, but I want to know how to get there from here. Must be very easy for the experts on this forum, but I am still a novice... Thanks in advance for any tip!
Code: Select all
`+-------+-------+-------+ | 1 3 8 | . . . | . 7 . | | 5 4 . | 2 . . | . . 1 | | 2 9 . | . 1 . | . . 4 | +-------+-------+-------+ | . . . | 8 . . | . 4 . | | . . 9 | . 4 . | 6 . . | | . 2 4 | . . 3 | . . . | +-------+-------+-------+ | 7 6 . | . 9 . | 4 . . | | 4 . . | . . 6 | 7 . 9 | | 9 8 . | . . . | 3 2 6 | +-------+-------+-------+`
GoSimon

Posts: 10
Joined: 11 November 2006

Focus on column 5... There is a naked triple (3 cells each containing a subset of a set of 3 numbers, so those 3 numbers cannot appear in any other cell)... The rest will be all singles...
udosuk

Posts: 2698
Joined: 17 July 2005

I didn't notice that one, but did find a naked quad in box 3 (upper right). 2589 I believe.
Hud

Posts: 570
Joined: 29 October 2005

udosuk wrote:Focus on column 5... There is a naked triple (3 cells each containing a subset of a set of 3 numbers, so those 3 numbers cannot appear in any other cell)... The rest will be all singles...

Thank you! Yes, indeed, there is a naked triple on column 5. I cannot believe how I missed it.

The Exhaustive Matrix Generator <http://www.hyperinfo.ca/Sudoku/> still gives me such mental challenges...
GoSimon

Posts: 10
Joined: 11 November 2006

GoSimon wrote:The Exhaustive Matrix Generator <http://www.hyperinfo.ca/Sudoku/> still gives me such mental challenges...
I never understood, why people with internet access are purchasing for puzzles or solving methods. There are a lot of sites with free puzzles for each level of diffculty and descriptions of solution techniques. Also in this forum you can find puzzles collections here, see e.g. this one for 100 handpicked challenges of this level.
ravel

Posts: 998
Joined: 21 February 2006

ravel wrote:
GoSimon wrote:The Exhaustive Matrix Generator <http://www.hyperinfo.ca/Sudoku/> still gives me such mental challenges...
I never understood, why people with internet access are purchasing for puzzles or solving methods. There are a lot of sites with free puzzles for each level of diffculty and descriptions of solution techniques. Also in this forum you can find puzzles collections here, see e.g. this one for 100 handpicked challenges of this level.

Hard copy. Portable. Read on the commute.

Computers are usefull, for most of us they are not "everywhere".
wapati
2010 Supporter

Posts: 527
Joined: 13 September 2006

I have nothing against people buying sudoku books etc... But here is what I think ravel's trying to argue:

For hard copies you can print out the puzzles you obtain from the internet...

Or, if you have a laptop/PDA/mobile phone (the more advanced models), it's not hard to obtain a solving software where you can input the puzzles data you obtain (for free) from the net... That way you can play even on the commute...

I guess is the same argument about ebooks vs paper books...
udosuk

Posts: 2698
Joined: 17 July 2005

### duo - no need trio

udosuk wrote:
GoSimon wrote:
Code: Select all
` 1 3 8 | . . . | . 7 .  5 4 . | 2 . . | . . 1  2 9 . | . 1 . | . . 4 -------+-------+------ . . . | 8 . . | . 4 .  . . 9 | . 4 . | 6 . .  . 2 4 | . . 3 | . . . -------+-------+------ 7 6 . | . 9 . | 4 . .  4 . . | . . 6 | 7 . 9  9 8 . | . . . | 3 2 6 `

Focus on column 5...
There is a naked triple...
The rest will be all singles...

c5 has a "hidden" duo { 3,8 }
which will do the same work as the "naked" trio
- therefore, this puzzle does not qualify as "superior"

Pat

Posts: 3789
Joined: 18 July 2005

### splendid

ravel wrote:in this forum you can find puzzles collections here,
see e.g. this one for 100 handpicked challenges of this level.

i enjoyed the "ulterior" collection and the "superior" collection -- note though that we do not have a collection of puzzles for the in-between range, which may be the level desired by GoSimon -- we have some good examples at this level but not any organized collection--

here's a splendid example -- try solving it on paper, no help from the computer --

bergoffen [ spoiler ] wrote:
Code: Select all
` . . . | . 7 . | 8 6 .  7 . . | . . 2 | 3 . .  . 6 8 | . 4 . | . . . -------+-------+------ . 3 7 | . . . | . . 4  . . 1 | . . . | 6 . .  5 . . | . . . | 7 2 . -------+-------+------ . . . | . 3 . | 4 5 .  . . 3 | 4 . . | . . 1  . 4 6 | . 1 . | . . . `

~ Pat

Pat

Posts: 3789
Joined: 18 July 2005

### Re: splendid

Pat wrote:
ravel wrote:in this forum you can find puzzles collections here,
see e.g. this one for 100 handpicked challenges of this level.

i enjoyed the "ulterior" collection and the "superior" collection -- note though that we do not have a collection of puzzles for the in-between range, which may be the level desired by GoSimon -- we have some good examples at this level but not any organized collection--

here's a splendid example -- try solving it on paper, no help from the computer --

bergoffen [ spoiler ] wrote:
Code: Select all
` . . . | . 7 . | 8 6 .  7 . . | . . 2 | 3 . .  . 6 8 | . 4 . | . . . -------+-------+------ . 3 7 | . . . | . . 4  . . 1 | . . . | 6 . .  5 . . | . . . | 7 2 . -------+-------+------ . . . | . 3 . | 4 5 .  . . 3 | 4 . . | . . 1  . 4 6 | . 1 . | . . . `

I am not good enough to solve Sudoku of this high level yet. This puzzle is harder than 5-star puzzles on my newspaper. After generating candidates and checking naked 2/3/4, I got stuck here...
Code: Select all
` . . . | . 7 . | 8 6 .  7 1 . | . . 2 | 3 4 .  . 6 8 | . 4 . | . . . -------+-------+------  6 3 7 | . . . | . . 4  . . 1 | . . . | 6 . .  5 . . | . . . | 7 2 . -------+-------+------  1 7 . | . 3 . | 4 5 6  . 5 3 | 4 . . | . . 1  . 4 6 | . 1 . | . . .`
GoSimon

Posts: 10
Joined: 11 November 2006

[Code:]

. . . | . 7 . | 8 6 .
7 1 . | . . 2 | 3 4 .
. 6 8 | . 4 . | . . .
-------+-------+------
6 3 7 | . . . | . . 4
. . 1 | . . . | 6 . .
5 . . | . . . | 7 2 .
-------+-------+------
1 7 . | . 3 . | 4 5 6
. 5 3 | 4 . . | . . 1
. 4 6 | . 1 . | . . .
[/code]

NAKED PAIR (Box): r8c7/r9c7 removes 9 from r8c8
NAKED PAIR (Box): r8c7/r9c7 removes 9 from r9c8
NAKED PAIR (Box): r8c7/r9c7 removes 2 from r9c9
NAKED PAIR (Box): r8c7/r9c7 removes 9 from r9c9
NAKED PAIR (Row): r2c3/r2c9 removes 5/9 from r2c4
NAKED PAIR (Row): r2c3/r2c9 removes 5/9 from r2c5
NAKED PAIR (Col): r8c7/r9c7 removes 2/9 from r3c7
NAKED PAIR (Col): r8c7/r9c7 removes 9 from r4c7

POINTING PAIR: 1s at r3c7/r3c8 points to r3c4, removing 1
POINTING PAIR: 1s at r3c7/r3c8 points to r3c6, removing 1
POINTING PAIR: 2s at r5c1/r5c2 points to r5c4, removing 2
POINTING PAIR: 2s at r5c1/r5c2 points to r5c5, removing 2
POINTING PAIR: 1s at r4c7/r4c8 points to r4c4, removing 1
POINTING PAIR: 1s at r4c7/r4c8 points to r4c6, removing 1
POINTING PAIR: 8s at r8c1/r9c1 points to r5c1, removing 8

NAKED QUAD (Box): r4c4/r4c5/r4c6/r5c5 removes 5/8/9 from r5c4
NAKED QUAD (Box): r4c4/r4c5/r4c6/r5c5 removes 5/8/9 from r5c6
NAKED QUAD (Box): r4c4/r4c5/r4c6/r5c5 removes 8/9 from r6c4
NAKED QUAD (Box): r4c4/r4c5/r4c6/r5c5 removes 8/9 from r6c5
NAKED QUAD (Box): r4c4/r4c5/r4c6/r5c5 removes 8/9 from r6c6
HIDDEN QUAD: 1/3/4/7 in box 5: r6c4 - 1/3/6 -> 1/3
HIDDEN QUAD: 1/3/4/7 in box 5: r6c6 - 1/3/4/6 -> 1/3/4

this solves singles at

r6c5 = 6
r2c5 = 8

and from here the puzzle is all singles.

hope that helps

strmckr
Some do, some teach, the rest look it up.

StrmCkr

Posts: 979
Joined: 05 September 2006

### Re: splendid

GoSimon wrote:... After generating candidates and checking naked 2/3/4, I got stuck here...
Code: Select all
` . . . | . 7 . | 8 6 .  7 1 . | . . 2 | 3 4 .  . 6 8 | . 4 . | . . . -------+-------+------  6 3 7 | . . . | . . 4  . . 1 | . . . | 6 . .  5 . . | . . . | 7 2 . -------+-------+------  1 7 . | . 3 . | 4 5 6  . 5 3 | 4 . . | . . 1  . 4 6 | . 1 . | . . .`

GoSimon, from where you got stuck, nothing other than singles, naked pairs and locked candidates is required to solve it... So you probably overlooked an easy move... I'd suggest you post the grid of your "stuck state" with pencilmarks and let our experts point out which move you've overlooked...

I have no idea why StrmCkr post all those fancy pointing pairs/quads... Perhaps he/she doesn't know there is a simple technique called "locked candidates"...

Edit: Points taken StrmCkr... Happy New Year!
Last edited by udosuk on Thu Dec 28, 2006 2:02 am, edited 1 time in total.
udosuk

Posts: 2698
Joined: 17 July 2005

well i don't exactly know where there stuck so i felt it was easier to list abunch of easy to spot moves are located.

(naked/pointing pairs are locked candidates thats what my solver calls them)

any one of them advances the puzzle beyond a stuck phase.

besides its what my solver printed out for steps to solve.
so i copy and pasted them all in.

:P

(and its he)
Some do, some teach, the rest look it up.

StrmCkr

Posts: 979
Joined: 05 September 2006

### re: splendid

GoSimon wrote:After generating candidates and checking naked 2/3/4, I got stuck here

Code: Select all
` . . . | . 7 . | 8 6 .  7 1 . | . . 2 | 3 4 .  . 6 8 | . 4 . | . . . -------+-------+------  6 3 7 | . . . | . . 4  . . 1 | . . . | 6 . .  5 . . | . . . | 7 2 . -------+-------+------  1 7 . | . 3 . | 4 5 6  . 5 3 | 4 . . | . . 1  . 4 6 | . 1 . | . . . `

hi GoSimon.

it seems many people have managed to learn all about "naked 2/3/4" while skipping over box-line interactions (or "Locked Candidates" as angusj calls them)

so you're missing much of the fun

~ Pat

Pat

Posts: 3789
Joined: 18 July 2005

### Re: splendid

Pat wrote:here's a splendid example -- try solving it on paper, no help from the computer --

bergoffen [ spoiler ] wrote:
Code: Select all
` . . . | . 7 . | 8 6 .  7 . . | . . 2 | 3 . .  . 6 8 | . 4 . | . . . -------+-------+------ . 3 7 | . . . | . . 4  . . 1 | . . . | 6 . .  5 . . | . . . | 7 2 . -------+-------+------ . . . | . 3 . | 4 5 .  . . 3 | 4 . . | . . 1  . 4 6 | . 1 . | . . . `

~ Pat

3 9 4 | 5 7 1 | 8 6 2
7 1 5 | 6 8 2 | 3 4 9
2 6 8 | 9 4 3 | 5 1 7
-------------------------
6 3 7 | 2 5 8 | 1 9 4
4 2 1 | 3 9 7 | 6 8 5
5 8 9 | 1 6 4 | 7 2 3
-------------------------
1 7 2 | 8 3 9 | 4 5 6
8 5 3 | 4 2 6 | 9 7 1
9 4 6 | 7 1 5 | 2 3 8

1 hour. No computer
Archangel

Posts: 5
Joined: 30 December 2006

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