[perl-python] exercise: partition a list by equivalence

[Xah Lee]

here's another interesting algorithmic exercise, again from part of a
larger program in the previous series.

Here's the original Perl documentation:

=pod

merge($pairings) takes a list of pairs, each pair indicates the
sameness
of the two indexes. Returns a partitioned list of same indexes.

For example, if the input is
merge( [ [1,2], [2,4], [5,6] ] );

that means 1 and 2 are the same. 2 and 4 are the same. Therefore
1==2==4. The result returned is

[[4,2,1],[6,5]];

(ordering of the returned list and sublists are not specified.)

=cut

For those of you unfamiliar with math lingoes, partition a list means
to create sublists, based on some criteria. In our case, the input list
comes in the form of pairs, and its members are the union of all
members in the pairs. The criterion for partition in our case is that
of equivalence, specified in the pairs input.

Try to write a Python code for this. In the Python code, the input
should be a list of couples. (for Perlers, sketch out the algorithm on
paper and try to code in Python directly.)

I'll post Perl & Python code tomorrow.

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 Xah
 xah at xahlee.org
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