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MathGroup Archive 1996

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Re: Pairings

  • To: mathgroup at smc.vnet.net
  • Subject: [mg4538] Re: [mg4434] Pairings
  • From: Allan Hayes <hay at haystack.demon.co.uk>
  • Date: Wed, 7 Aug 1996 04:17:44 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

Robert Pratt <rpratt at math.unc.edu>
[mg4434] Pairings
writes

> I want a function that finds, given n, all pairings of Range[n]
> excluding {1,2}, {2,3}, {n-2,n-1}, and {n-1,n}........

Robert:
Needs["DiscreteMath`Combinatorica`"]

DeleteCases[KSubsets[Range[7],2], {a_,b_}/;b==a+1]//Timing
{0.05 Second,
{{1, 3}, {1, 4}, {1, 5}, {1, 6}, {1, 7}, {2, 4}, {2, 5}, {2, 6},
 {2, 7}, {3, 5}, {3, 6}, {3, 7}, {4, 6}, {4, 7}, {5, 7}}
}

Allan Hayes
hay at haystack.demon.co.uk

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