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Re^10: Finding All Paths From a Graph From a Given Source and End Node

by LanX (Cardinal)
on Nov 02, 2010 at 15:23 UTC ( #869020=note: print w/replies, xml ) Need Help??


in reply to Re^9: Finding All Paths From a Graph From a Given Source and End Node
in thread Finding All Paths From a Graph From a Given Source and End Node

I'd try your routine here,but I can't work out where I supply the start and end?

Globals! See the post before. (there is no point in passing them as long as you don't use any divide and conquer approach)

or just:

use strict; use warnings; use Data::Dumper; $|=1; my $start="B"; my $stop="E"; my %graph =( 'F' => ['B','C','E'], 'A' => ['B','C'], 'D' => ['B'], 'C' => ['A','E','F'], 'E' => ['C','F'], 'B' => ['A','E','F'] ); $start="A"; $stop="Z"; %graph =( A => ["N", "W", "J", "L", "C", "E", "X", "T", "O", "H"], C => ["Z", "J", "Q", "U", "S", "T", "N", "P", "D", "O"], E => ["P", "G", "U", "F", "X", "A", "Y", "K"], H => ["W", "O", "J"], J => ["Z", "U", "B", "Q", "N", "I", "V", "F", "C", "P"], K => ["X", "H", "J", "C", "P", "W", "E", "S", "Q"], L => ["C", "B", "V", "A", "S", "J", "O", "H"], N => ["R", "G", "K", "N", "Q", "W", "C", "U", "E", "V"], O => ["K", "G", "X", "A", "Z", "W"], P => ["O", "G", "F", "T", "E", "U", "L", "H", "B", "R"], Q => ["V", "N", "X", "U", "D", "M", "S", "C", "R", "G"], R => ["D", "S", "K", "X", "O", "U"], S => ["Q", "E", "T", "P", "G", "Z"], U => ["Y", "V", "U", "X", "R", "W", "M", "G", "K", "N", "A"], W => ["P", "E", "G", "Y"], X => ["Z", "H", "R", "L", "J", "W", "A", "E", "X", "T", "D"], Y => ["J", "X", "G"], Z => ["K", "A", "Z"], ); my $anzahl=0; my $time0=time; track($start); { my %seen; sub track { my @path=@_; my $last=$path[-1]; $seen{$last}=1; for my $next (@{$graph{$last}}) { next if $seen{$next}; if ($next eq $stop) { #print join ("->",@path,$stop),"\n"; $anzahl++; print "$anzahl at ",time-$time0,"\n" if $anzahl%10000==0; } else { track(@path,$next); } } delete $seen{$last}; } } print $anzahl;

Of course @path could be global too and the recursion could be liniarized...

Not talking about nifty short circuit algorithms...

Cheers Rolf

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