Triplets :: S=('b,c|a', 'a,c|d', 'd,e|b'), Species :: L={a,b,c,d,e} TreeConstruct(S): 1.] Let L be the set of species in S. Build G(L) the auxillary graph. 2.] Let C1,C2....Cq be the set of connected components in G(L). 3.] If q>1,then - For i=1,2.....q, let S(i) be the set of triplets in S labeled by the set of leaves in C(i). - Let T(i) = TreeConstruct(S(i)) - Let T be a tree formed by connecting all T(i) with the same parent node. Return T. 4.]If q=1 & C1 contains exactly one leaf,return the leaf ,else return fail. ##```## use strict; use warnings; use Graph; @ARGV = ('b,c|a', 'a,c|d', 'd,e|b') unless @ARGV; my %HoA; foreach ( @ARGV ) { m/^([a-z])[,]([a-z])[|]([a-z])\$/ ; push @{\$HoA{\$1}}, \$2; } print "\n===========\@HoA=====\n"; print "from->to\n"; while (my (\$key, \$values) = each %HoA) { print \$key, "=> [", join(',', @\$values), "]\n"; } my \$g = Graph->new( undirected => 1 ); for my \$src ( keys %HoA ) { for my \$tgt ( @{ \$HoA{\$src} } ) { \$g->add_edge(\$src, \$tgt); } } my @subgraphs = \$g->connected_components; my @allgraphs; for my \$subgraph ( @subgraphs ) { push @allgraphs, {}; for my \$node ( @\$subgraph ) { if ( exists \$HoA{ \$node } ) { \$allgraphs[-1]{\$node} = [ @{ \$HoA{\$node} } ]; } } } print "----connected components------------"; use YAML; print Dump \@allgraphs; -------------OUTPUT---------------- ===========@HoA===== from->to a=> [c] b=> [c] d=> [e] ----connected components--------------- - a: - c b: - c - d: - e ```