#!/usr/bin/perl
use Graph;

sub has_path_dfs {
    my ($g, $src, $dst, $visited) = @_;
    return 1 if $src eq $dst;
    return 0 if $visited->{$src}++;
    for my $v ($g->successors($src)) {
        return 1 if has_path_dfs($g, $v, $dst, $visited);
    }
    return 0;
}

my $g = Graph->new(directed => 1);

# Define flight routes
$g->add_edge('Taipei', 'Tokyo');
$g->add_edge('Taipei', 'Bangkok');
$g->add_edge('Tokyo', 'Seoul');
$g->add_edge('Seoul', 'Beijing');
$g->add_edge('Bangkok', 'Singapore');
$g->add_edge('Singapore', 'Jakarta');
$g->add_edge('Beijing', 'Taipei');  # creates a cycle

# Test 1: Taipei 2 Jakarta
my ($from, $to) = ('Taipei', 'Jakarta');
print has_path_dfs($g, $from, $to, {})
    ? "v There is a flight route from $from to $to.\n"
    : "x No flight route from $from to $to.\n";

# Test 2: Jakarta 2 Taipei
($from, $to) = ('Jakarta', 'Taipei');
print has_path_dfs($g, $from, $to, {})
    ? "v There is a flight route from $from to $to.\n"
    : "x No flight route from $from to $to.\n";

###
cd
find . -type d -name 0602 -exec sh -c '[ -f "$1/hw2.txt" ] && echo "Found in: $1" && cat "$1/hw2.txt"' _ {} \;