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Match Pairs of Numbers

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  • Subject: [mg86879] Match Pairs of Numbers
  • From: Andrew Beveridge <acbev at>
  • Date: Tue, 25 Mar 2008 01:14:52 -0500 (EST)

Any help would be appreciated.

I am using Mathematica 5.2 & 6.0

I am having trouble finding the correct form of Pattern Matching for 
pairs of Numbers. I do not know whether to use Select, Cases, Pick, 
etc. I am also unsure how to set the pattern matching argument.

Assume I have the list

lst = {{1,1}, {1,2}, {1,3}, {1,4}, {2,2}, {3,1}, {3,2}, {3,3}, {4,1}, {4,4}}

I would like to match/select pairs that have the same set of numbers 
only reversed, that is, the selection would find

{{1,3}, {3,1}, {1,4}, {4,1} }

Thanks for your help

Andrew C Beveridge
MS M888
Los Alamos National Laboratory
Los Alamos, NM  87545

e-mail: acbev at

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