Re^5: Finding All Paths From a Graph From a Given Source and End Node

choroba,
As I indicated before, certain graphs, order of traversal and endpoints will determine how well the short circuiting approach fairs. I have asked for advice concerning this at Short Circuiting DFS Graph Traversal. My fastest normal solution is below.

#!/usr/bin/perl
use strict;
use warnings;

my %graph = (
    R => [qw/L J Z/], L => [qw/R J X/], J => [qw/R L X Z/], Z => [qw/R
+ J X/], X => [qw/L J Z F D/],
    F => [qw/X D/],   D => [qw/Q F X/], Q => [qw/B U D/],   B => [qw/Q
+ P M/], P => [qw/B U/],
    U => [qw/Q P S/], M => [qw/B S/],   S => [qw/U M/],
);

my $n;
my %node_to_int = map {$_ => $n++} keys %graph;

my $routes = find_paths('D', 'M', \%graph);
print "$_\n" for @$routes;

sub find_paths {
    my ($beg, $end, $graph) = @_;
    my (@work, @solution);
    for (@{$graph->{$beg}}) {
        if ($_ eq $end) {
            push @solution, "$beg->$end";
            next;
        }
        my $seen = '';
        vec($seen, $node_to_int{$_}, 1) = 1;
        vec($seen, $node_to_int{$beg}, 1) = 1;
        push @work, ["$beg->$_", $_, $seen];
    }
    while (@work) {
        my $item = pop @work;
        my ($path, $curr, $seen) = @$item;
        for my $node (@{$graph->{$curr}}) {
            my $bit = $node_to_int{$node};
            next if vec($seen, $bit, 1);
            if ($node eq $end) {
                push @solution, "$path->$end";
                next;
            }
            my $new_seen = $seen;
            vec($new_seen, $bit, 1) = 1;
            push @work, ["$path->$node", $node, $new_seen];
        }
    }
    return \@solution;
}
[download]

Cheers - L~R

Comment on Re^5: Finding All Paths From a Graph From a Given Source and End Node Download Code

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Re^6: Finding All Paths From a Graph From a Given Source and End Node by neversaint (Deacon) on Nov 01, 2010 at 04:59 UTC
Dear Limbic, I tried the following graph and predertimined start and position in code below. But why It gives empty result? Please refer to the visualization of the graph here (http://graph.gafol.net/cESwUMeNd) . my %graph2 = ( 'read145404_1' => [ 'read231054_2', 'read250449_2' ], 'read250449_2' => [ 'read359463_1', 'read691358_1', 'read937013_1' ], 'read231054_2' => [ 'read691358_1', 'read359463_1', 'read937013_1' ] ); my $routes = find_paths('read145404_1', 'read691358_1', \%graph2); sub find_paths { my ($beg, $end, $graph) = @_; my $n; my %node_to_int = map {$_ => $n++} keys %graph; my (@work, @solution); for (@{$graph->{$beg}}) { if ($_ eq $end) { push @solution, "$beg->$end"; next; } my $seen = ''; vec($seen, $node_to_int{$_}, 1) = 1; vec($seen, $node_to_int{$beg}, 1) = 1; push @work, ["$beg->$_", $_, $seen]; } while (@work) { my $item = pop @work; my ($path, $curr, $seen) = @$item; for my $node (@{$graph->{$curr}}) { my $bit = $node_to_int{$node}; next if vec($seen, $bit, 1); if ($node eq $end) { push @solution, "$path $end"; next; } my $new_seen = $seen; vec($new_seen, $bit, 1) = 1; push @work, ["$path->$node", $node, $new_seen]; } } # Return print Dumper \@solution; return \@solution; } [download] --- neversaint and everlastingly indebted.......	[reply] [d/l]
Re^7: Finding All Paths From a Graph From a Given Source and End Node by Limbic~Region (Chancellor) on Nov 01, 2010 at 14:56 UTC
neversaint, The problem was that the %node_to_int lookup assumed all possible nodes would also be keys in graph. One way to fix it would be to have nodes that don't connect anywhere as `node => []` (empty array ref). I chose to provide a solution below that doesn't require the user to type more than is necessary when building the graph. Read more... (2 kB) Cheers - L~R	[reply] [d/l] [select]