## A not so nice....Nice Loop,

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

### A not so nice....Nice Loop,

I need some help with this “Nice Loop”. It was my understanding that if two of the adjacent links in a Nice Loop are weak links then that candidate could be removed at the point of discontinuity. Conversely, if the adjacent links have a strong inference, a candidate can be placed at the point of the discontinuity.

Below is the puzzle in question. The cells being referred to labeled (a), (b), (c), (d) and (e). The cell at (r8c1) looks like an (8) should be able to be placed there. Not so, I see the (8) should be eliminated instead.

Hopefully, somebody can tell be where I have gone astray. Many thanks for your help.

Code: Select all
`  *-----------* |..8|729|..5| |917|453|268| |325|186|497| |---+---+---| |7..|.4.|..2| |..1|.72|5..| |2..|.3.|.7.| |---+---+---| |5.4|217|...| |.72|394|.51| |1..|568|724| *-----------*  *--------------------------------------------------------------------* | 46     46     8      | 7      2      9      | 13     13     5      | | 9      1      7      | 4      5      3      | 2      6      8      | | 3      2      5      | 1      8      6      | 4      9      7      | |----------------------+----------------------+----------------------| | 7      3589   369    | 689    4      15     | 13689  138    2      | | 48d     3489   1      | 689    7      2      | 5      348c    369    | | 2      4589   69     | 689    3      15     | 1689   7      69     | |----------------------+----------------------+----------------------| | 5      68     4      | 2      1      7      | 3689   38b     369    | | 68e     7      2      | 3      9      4      | 68a     5      1      | | 1      39     39     | 5      6      8      | 7      2      4      | *--------------------------------------------------------------------*`
Jasper32

Posts: 60
Joined: 04 January 2008

### nice loop

the loop should consist of alternating strong and weak links. In your example you´ve got two strong links which you want use as a proof for the 8 in R8C1 - but the rest of your links are weak. This way the loop won´t work.
But you can find a very nice unique rectangle in row 1 and 4

13 13
... ...
... ...
13689 138

together with that cell 689 in C4 it gives you a locked set of the candidates 689 - you can exclude all 689 candidates in row 4 except c4/7/8
bib21

Posts: 1
Joined: 26 October 2008

### Re: A not so nice....Nice Loop,

Jasper32 wrote:Hopefully, somebody can tell be where I have gone astray.

Your cells don't even form a chain from what I can see. Thus, there's no chance they form a nice loop.
daj95376
2014 Supporter

Posts: 2624
Joined: 15 May 2006

Jasper, if you clean up the two naked fours you won't have to sweat any loops at all.

Here's a good link for nice loops: http://www.paulspages.co.uk/sudokuxp/howtosolve/niceloops.htm

Bib, how do you figure the UR forces a locked set on 6, 8, and 9?

Luke
2015 Supporter

Posts: 435
Joined: 06 August 2006
Location: Southern Northern California