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A4N10
https://www.calcudoku.org/forum/viewtopic.php?f=16&t=1083
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Author:  paulv66  [ Tue Aug 07, 2018 12:39 am ]
Post subject:  A4N10

I've been working my way through Advanced Puzzles IV and I'm really struggling with the above 10x10 no-op.

I must have made about twenty attempts at this stage, but keep running into a dead end. I've gone through it very methodically and I think I've avoided making any unwarranted assumptions or excluding alternative solutions to particular cells, but I'm now totally bamboozled.

This has happened to me before where I've assumed that a puzzle must have been misprinted, but that has never actually proved to be the case, so I'm fairly sure the same thing applies here. However, before I spend any more time on it, I would be interested in hearing if anyone has actually managed to solve it. I'm not looking for any hints as I want to solve it under my own steam, but I would like the reassurance that it is actually solvable.

Author:  michaele  [ Tue Aug 07, 2018 5:32 am ]
Post subject:  Re: A4N10

I have solved this puzzle. I did not use any trial and error, it is solvable using logic only.

I like the no-op puzzles, but it is very easy to make a mistake.

Author:  paulv66  [ Tue Aug 07, 2018 10:03 am ]
Post subject:  Re: A4N10

michaele wrote:
I have solved this puzzle. I did not use any trial and error, it is solvable using logic only.

I like the no-op puzzles, but it is very easy to make a mistake.


Thanks Michaele

It's good to know I'm not just wasting my time on it. I have been going through it step by step (and column by column), but I must have overlooked some possible combination for one of the columns. I'll have another go at it later today.

Author:  clm  [ Tue Aug 07, 2018 2:40 pm ]
Post subject:  Re: A4N10

paulv66 wrote:
michaele wrote:
I have solved this puzzle. I did not use any trial and error, it is solvable using logic only.

I like the no-op puzzles, but it is very easy to make a mistake.


Thanks Michaele

It's good to know I'm not just wasting my time on it. I have been going through it step by step (and column by column), but I must have overlooked some possible combination for one of the columns. I'll have another go at it later today.


I agree with michaele that it is easy to make a mistake since in a no-op you must consider all possible operators and all possible operands. For the moment I have solved and sent 9 (out of 11) of the "nearly impossible" 6* puzzles and this one, the 85, A4N10, in my opinion, has a "medium" difficulty inside this group (in fact some of the 5* are more difficult).

Author:  paulv66  [ Tue Aug 07, 2018 5:58 pm ]
Post subject:  Re: A4N10

Thanks folks.

I went back over my work and discovered that I had made a mistake early on in column A, where I had assumed that there was one particular value in A8 (out of two possibilities) that must be correct as I couldn't find any way of resolving the remaining cells in that column if I put in the other number. But there was one combination I had overlooked and when I put this in, I was able to solve the problem - eventually.

That's 7 of the 11 'nearly impossible' done. The two going from -1 to +7 look particularly challenging.

Author:  michaele  [ Thu Aug 09, 2018 4:00 am ]
Post subject:  Re: A4N10

I had another look at how I solved this puzzle, I found it to be an interesting puzzle to solve because I found a clue that I don’t think I had ever found before in any other puzzle. I assumed that finding this difficult to find clue was what made it deserving of the “nearly impossible” category, although after finding this clue it was all very straight forward to complete the puzzle.

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