## BUG+1 Question

Everything about Sudoku that doesn't fit in one of the other sections

### BUG+1 Question

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` *-----------* |...|.9.|8.1| |392|..8|...| |...|...|.2.| |---+---+---| |.3.|6..|5.2| |6..|.4.|..3| |1.9|..3|.4.| |---+---+---| |.8.|...|...| |...|8..|465| |4.3|.5.|...| *-----------* # original`

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`# reduced to BUG+1 at [r7c6]## <1> occurs three times in buddy cells to [r7c6]# <4> occurs twice       in buddy cells to [r7c6]# <6> occurs twice       in buddy cells to [r7c6]## Simple Sudoku says [r7c6]=4 ... and it solves puzzle!!! *--------------------------------------------------* | 5    4    67   | 23   9    26   | 8    37   1    | | 3    9    2    | 14   17   8    | 67   5    46   | | 78   1    68   | 35   67   45   | 39   2    49   | |----------------+----------------+----------------| | 78   3    4    | 6    18   17   | 5    9    2    | | 6    2    78   | 59   4    59   | 1    78   3    | | 1    5    9    | 27   28   3    | 67   4    68   | |----------------+----------------+----------------| | 29   8    5    | 49   26  #146  | 39   13   7    | | 29   7    1    | 8    3    29   | 4    6    5    | | 4    6    3    | 17   5    79   | 2    18   89   | *--------------------------------------------------*`

Why isn't [r7c6]=1 correct???
Last edited by daj95376 on Sat Nov 11, 2006 10:49 am, edited 1 time in total.
daj95376
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I cannot get SS to like this puzzle. Check your grid, both of them?
wapati
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On my computer, SS doesn't have any problems with my puzzle or the PM. Don't copy the (#) characters into SS.

I checked to see if I eliminated too many <4> values by accident. I couldn't find an anomaly. Here's the full solution up to the BUG+1.

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`r4c3    =  4     Hidden Singler8c5    =  3     Hidden Single  c7    -  67    Naked  Pair  c1    -  578   Naked  Tripler7c3    =  5     Hidden Singler9c2    =  6     Hidden Single    b4  -  78    Naked  Pair  c2    -  25    Naked  Pairr8      -  17    Naked  Pair    b1  -  1     Locked Candidate (1)r7c6    <> 29    Unique Rectangle Type 1r4c8    =  9 (2) Forcing Chain/Net on [r7c1]r7c9    =  7 (2) Forcing Chain/Net on [r7c1]r5c7    =  1     Naked  Singler5      -  78    Naked  Pairr9c6    <> 1     XY-Chain on [r4c6]r1c1    =  5     [r1c1]=7 => [r7c7]=EMPTY    (hidden,naked) = ( 0,31)r2c8    =  5     Hidden Singler1c2    =  4     [r1c2]=7 => [r7c8]=EMPTY    (hidden,naked) = ( 0,28)r3      -  1678  Naked  Quad    b3  -  6     Locked Candidate (1)r3c3    <> 17    Unique Rectangle Type 1r3c2    =  1     Hidden Singler8c2    =  7     Naked  Singler8c3    =  1     Naked  Single  c38   -  7     X-Wingr6c5    <> 7     Templates (A)r5c6    <> 2     XY-Chain on [r1c6]r5c4    <> 2     XY-Chain on [r1c4]r5c2    =  2     Hidden Singler6c2    =  5     Naked  Singler7c4    <> 2     XY-Chain on [r1c4]r9c4    <> 2     XY-Chain on [r1c4]r9c6    <> 2     XY-Chain on [r1c6]r9c7    =  2     Hidden Singler3c4    <> 4     XY-Chain on [r3c6]r9c4    <> 9     XY-Chain on [r5c4]r2c4    <> 7     XY-Chain on [r2c7]    b2  -  7     Locked Candidate (1)r7c4    <> 1     XY-Chain on [r2c4]r7c5    <> 1     XY-Chain on [r2c5]`
daj95376
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### Re: BUG+1 Question

daj95376 wrote:Why isn't [r7c6]=1 correct???

Because there are exactly two 1s in each row, col, and box. Look at the 9s instead.

Your puzzle may not fit the formal BUG+1 definitions, but it surely is one. The extra candidate is just not in the polyvalued cell ... a rarity I suspect.
ronk
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Location: Southeastern USA

daj95376 wrote:
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`# reduced to BUG+1 at [r7c6] # # <1> occurs three times in buddy cells # <4> occurs twice       in buddy cells # <6> occurs twice       in buddy cells # # Simple Sudoku says [r7c6]=4 ... and it solves puzzle!!!  *--------------------------------------------------*  | 5    4    67   | 23   9    26   | 8    37   1    |  | 3    9    2    | 14   17   8    | 67   5    46   |  | 78   1    68   | 35   67   45   | 39   2    49   |  |----------------+----------------+----------------|  | 78   3    4    | 6    18   17   | 5    9    2    |  | 6    2    78   | 59   4    59   | 1    78   3    |  | 1    5    9    | 27   28   3    | 67   4    68   |  |----------------+----------------+----------------|  | 29   8    5    | 49   26  #146  | 39   13   7    |  | 29   7    1    | 8    3    29   | 4    6    5    |  | 4    6    3    | 17   5    79   | 2    18   89   |  *--------------------------------------------------* `

Why isn't [r7c6]=1 correct???

Ronk is right, <1> doesn't occur three times in buddy cells, the 9s do. This is indeed a very strange situation, where your extensive use of chains has created a BUG+1 grid where the '+1' isn't in the polyvalued cell. I'm not quite sure how these grids should be dealt with, in case there's more of them coming up. In this case, apparently the +1 cell is r7c4, but why that one? It has 2 buddies in the box and row, but only 1 in the column. Both r8c6 and r9c6 has 2 buddies in the box and column, but only one in the row.

RW
RW
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Just before logging in today, it hit me that there may be more to a BUG than the bi-value constraint. So, I went back to the definition and discovered a bi-location constraint as well.

Jeff: A Bivalue Universal Grave (BUG) is any grid in which all the unsolved cells have two candidates, and if a candidate exists in a row, column, or box, it shows up exactly twice.

I have egg all over my face for not checking the definition -- and 9s -- first. Sorry, I need to update my BUG module!!!

Thanks ronk and RW for catching the anomaly!!! Yes, this is the first time that the bi-value constraint was insufficient for my solver.

ronk and RW: I was not clear in my use of the term buddy cells. What I meant to say is that <1> occurs in three buddy cells to [r7c6]. Likewise for the <4> and <6> values being in two buddy cells to [r7c6]. Normally, this would have been sufficient to force [r7c6]=1. Right? (I've updated my previous posts to reflect this.)
daj95376
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daj95376 wrote:What I meant to say is that <1> occurs in three buddy cells to [r7c6]. Likewise for the <4> and <6> values being in two buddy cells to [r7c6]. Normally, this would have been sufficient to force [r7c6]=1. Right?

No, I don't think it's normally sufficient to force the +1 value. It must appear in two "buddy cells" of each unit. In this case there's only one buddy for the <1> in all 3 units. As there is also only one buddy for the <4> and <6>.

RW
RW
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RW wrote:
daj95376 wrote:What I meant to say is that <1> occurs in three buddy cells to [r7c6]. Likewise for the <4> and <6> values being in two buddy cells to [r7c6]. Normally, this would have been sufficient to force [r7c6]=1. Right?

No, I don't think it's normally sufficient to force the +1 value. It must appear in two "buddy cells" of each unit. In this case there's only one buddy for the <1> in all 3 units. As there is also only one buddy for the <4> and <6>.

RW

Okay, I think I understand where I'm going wrong. Thanks for all the help!
daj95376
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### Re: BUG+1 Question

ronk wrote:Your puzzle may not fit the formal BUG+1 definitions, but it surely is one. The extra candidate is just not in the polyvalued cell ... a rarity I suspect.

I'm unable to eliminate a candidate to yield a BUG grid, so now think daj's grid is not actually a BUG+1.
ronk
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### Re: BUG+1 Question

ronk wrote:
ronk wrote:Your puzzle may not fit the formal BUG+1 definitions, but it surely is one. The extra candidate is just not in the polyvalued cell ... a rarity I suspect.

I'm unable to eliminate a candidate to yield a BUG grid, so now think daj's grid is not actually a BUG+1.

Correct! It only appears to be a BUG+1. Once I reviewed Jeff's thread on BUGs, and merged it with what your and RW were saying, I realized that I'd completely misunderstood BUG+1.

After correcting my solver, this puzzle -- and several others that I tested -- suddenly weren't BUG+1 anymore.

Thanks again to you and RW for getting me past my confusion on BUG+1 !!!
daj95376
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The grid that daj posted is a nice example of a BUG trap or a pseudoBUG...........

as it is easy to see the only trivalue cell in the grid...none of its candidates occurs 3 times in that cell's row/column/box

tarek

tarek

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Code: Select all
`I list some puzzles with BUG I found.The number is the rest empty cells(>34) when BUG is appeared.75.6.3.946248.9.35....54...46..9..83....3.9..93.....52.........18.9.5.2724.3.1.69   4378.4.3.9119.7.5.64.........978....42.....2.7.26..74.858........64.1.7.385372.8.19   4229.5.863115.6.9.47......5..37.1...84.8.39...662...4.53..2......94.2.3.1581.9.7.62   4028.91.43.61473.59.39......172..9.81.54.38.72........5.47.85.96.95.26.14......9..5   3932.7.1.4949.523.78.......2.56.....142.....9.691.....37.49......15.4.8.92832957461   3845.98.12.83.26.75.........861....54.39..4.26...4..68..28.47931.143658972.....2.8.   3816985.34.42.91.68..7.......24..6893.95....826..6.....461.27.45.7924851635.4......   3742.9.3.1616.5.4.37....1.4..21..45.83..4.32...53..9..42.4..59...68.4.139595.368.74   3626.3.819438.2.9675..9...28349..8.536......42.65..3..19....2..6.92.8.735117.5.3.42   35`

Did other puzzles have more empty grids than these?
Last edited by Eioru on Sat Oct 18, 2008 12:40 am, edited 1 time in total.
Eioru

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Eioru wrote:I list some puzzles with BUG I found.
The number is the rest empty grids(>34) when BUG is appeared.

I didn't put forth much effort, but I found none. What set of techniques is required to reveal your BUG+1 patterns

BTW what you're calling "grid" is almost universally called "cell."
ronk
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### Re: BUG+1 Question

daj95376 wrote:After correcting my solver, this puzzle -- and several others that I tested -- suddenly weren't BUG+1 anymore.

Well, lucky you! This is what my solver gives me:
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`.-----------.----------------.------------.| 5   4  67 | 23  9    26    | 8   37  1  || 3   9  2  | 14  17   8     | 67  5   46 || 78  1  68 | 35  67   45    | 39  2   49 |:-----------+----------------+------------:| 78  3  4  | 6   18   17    | 5   9   2  || 6   2  78 | 59  4    59    | 1   78  3  || 1   5  9  | 27  28   3     | 67  4   68 |:-----------+----------------+------------:| 29  8  5  | 49  26  -1-4-6 | 39  13  7  || 29  7  1  | 8   3    29    | 4   6   5  || 4   6  3  | 17  5    79    | 2   18  89 |'-----------'----------------'------------'Bivalue Universal Grave + 1 => r7c6<>1246`

I still try to figure out where the r7c6<>2 comes from

Thanks anyway for the nice test case...
hobiwan
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My solver returns a short XY-Chain for [r8c6]<>9. While reviewing the PM, it appears that this elimination might also be the result of an ALS using [r27c4]=149 and [r9c46]=179. Am I even close
daj95376
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