我想找到从源到汇的所有路径.预期：
(3 11 17 24 32 39 45) (3 11 18 26 33 39 45) (3 11 18 26 33 40 46) (3 11 18 26 33 40 47) (3 11 19 27 33 39 45) (3 11 19 27 33 40 46) (3 11 19 27 33 40 47) (3 11 19 27 34 40 46) (3 11 19 27 34 40 47) (6 12 20 27 33 39 45) (6 12 20 27 33 40 46) (6 12 20 27 33 40 47) (6 12 20 27 34 40 46) (6 12 20 27 34 40 47)
在我的代码中,我知道如何访问每个顶点,但我如何正确记住并组装完整路径？
use 5.028;
use feature 'signatures';
use strictures;
use Graph qw();
my $g = Graph->new(directed => 1);
for my $edge_tuple (qw(
3-11 6-12 11-17 11-18 11-19 12-20 17-24 18-26 19-27 20-27 24-32 26-33
27-33 27-34 32-39 33-39 33-40 34-40 39-45 40-46 40-47
)) {
my ($from,$to) = split '-',$edge_tuple;
$g->add_edge($from,$to);
}
say join ';',$g->source_vertices;
say join ';',$g->sink_vertices;
sub visit($g,$v,$p) {
push @$p,$v;
if ($g->is_sink_vertex($v)) {
return;
} else {
for my $s ($g->successors($v)) {
visit($g,$s,$p)
}
}
}
my $p = [];
for my $v ($g->source_vertices) {
visit($g,$p);
}
use Data::Dumper; say Dumper $p;
解决方法
我修改了你的代码,将部分路径传递给visit(),并让visit()从提供的部分路径返回所有可能的完整路径：
sub visit($g,$path) {
my $v = $path->[-1];
if ($g->is_sink_vertex($v)) {
return $path;
} else {
my @more;
for my $s ($g->successors($v)) {
push @more,visit($g,[ @$path,$s ])
}
return @more;
}
}
my @p;
for my $v ($g->source_vertices) {
push @p,[$v]);
}
use Data::Dumper; say Dumper @p;
然后可以使用map减少循环：
sub visit($g,$path) {
my $v = $path->[-1];
if ($g->is_sink_vertex($v)) {
return $path;
} else {
return map { visit($g,$_ ]) } $g->successors($v);
}
}
my @p = map { visit($g,[$_]) } $g->source_vertices;