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GeneralRe: Sounding off on the responses Pin
Member 798912219-Mar-18 4:15
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GeneralRe: Sounding off on the responses Pin
PIEBALDconsult19-Mar-18 10:32
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W Balboos, GHB21-Mar-18 1:17
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GeneralRe: Difficult-to-solve Sudoku wanted Pin
Fueled By Caffeine19-Mar-18 3:23
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Member 798912219-Mar-18 3:33
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GeneralRe: Difficult-to-solve Sudoku wanted Pin
PIEBALDconsult19-Mar-18 5:02
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GeneralRe: Difficult-to-solve Sudoku wanted Pin
Member 798912219-Mar-18 5:57
MemberMember 798912219-Mar-18 5:57 
"When in doubt, use brute force" (attributed to Ken Thompson).

In the basic Algorithms course at the University (a long time ago Smile | :) ) we of course learned sorting algorithms - and learned that when sort a subsequence of say five or six numbers, managing a quicksort costs more administration than what you save. So, below 8 elements in a subsequence, you switch to a near-zero administration bubble sort. At least half of the students (myself as one) refused to take the professor's claim at face value, doing timing with quicksort (or other nlogn method) down to sorting even two elements. Surprise, surprise: The professor was right: With less than roughly 10 elements, no.brain bubble sort IS more efficient than the intellectually superior nlogn methods, if your goal is to get the job done.

I use similar reasoning in my backtracking Sudoku: In a few places I make "unneccesary" cheks, but managing the required data structures to suppress the checks would cost more resources than simply doing them. You shouldn't spend too much time on supressing a few checks taking 30 nanoseconds to execute! My solver handles all the games I have tried in less than five milliseconds. I was hoping for someone to dig up games that is not handled well by backtracking methods - but that seems to be more difficult than solving a Sudoku game Smile | :)

Do you still believe that "a backtracking approach is not appropriate to the challenge"? Is that because its simplicity is intellectualy inferior, or do you believe that it is less efficient (i.e. slower) than other methods?

I would be very curious to see an algorithmic encoding of these "logic" or "analythic" solution methods, strongly suspecting that the analysis required to analythically determine that "It is no use trying the value 3 in that square" would take far more resources than simply putting a 3 in there and see if all conditions are satisfied - even though some people condsider that intellectually inferior.

The difficulty is to have those guys using "logic" or "analythic" solutions come out of magician mode and explain how they know that a 4 rather than a 3 would be suitable in a given square. If they manage to explain it, it will turn out just as algorithmic as backtracking.
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Dezhi Zhao19-Mar-18 5:21
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Member 798912219-Mar-18 9:18
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QuestionKid Sister Safe These Days... Pin
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