Programming puzzles: processing lists!

08162017, 06:58 PM
Post: #189




RE: Programming puzzles: processing lists!
(08162017 03:03 PM)DavidM Wrote:(08162017 12:51 PM)pdo Wrote: Hello, Hi David, Sorry for being cryptic, it was just a quick post after my lunchtime reading (this forum). My reasoning is as follows: given a list of N items (N even) take the first item, then you have a choice of N1 items with which to pair it. Choose one, then remove both items from the list. This will leave a list of N2 items to which you can apply the same procedure, this time giving a choice of N3 items, and so on. This gives a total number of possible "routes" through this process of (N1)(N3)(N5)...1. For a proper proof we'd need to show each route gives a unique result  seems plausible to me, but I think it requires a bit more thought to put into words. As far as a program to compute the pairings goes, I was imagining a function recursing on the list in a similar way to my description above, but collecting all the possible choices and collating the results. I can imagine how to do this in a language like Lisp, for example, but on the way home from work I got to thinking how I would implement this in RPL, and to be honest I'm not sure how I would go about it. Stuff to ponder... Paul 

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