Dear Masters,

I have a code that try to find the Eulerian path like this. But somehow it doesn't work.
What's wrong with the code?

` use strict;
use warnings;
use Data::Dumper;
use Carp;
my %graphs = ( 1 => [2,3], 2 => [1,3,4,5], 3 =>[1,2,4,5], 4 => [2,
+3,5], 5 => [2,3,4]);
my @path = eulerPath(%graphs);
sub eulerPath {
my %graph = @_;
# count the number of vertices with odd degree
my @odd = ();
foreach my $vert ( sort keys %graph ) {
my @edg = @{ $graph{$vert} };
my $size = scalar(@edg);
if ( $size % 2 != 0 ) {
push @odd, $vert;
}
}
push @odd, ( keys %graph )[0];
if ( scalar(@odd) > 3 ) {
return "None";
}
my @stack = ( $odd[0] );
my @path = ();
while (@stack) {
my $v = $stack[-1];
if ( $graph{$v} ) {
my $u = ( @{ $graph{$v} } )[0];
push @stack, $u;
# Find index of vertice v in graph{$u}
my @graphu = @{ $graph{$u} }; # This is line 54.
my ($index) = grep $graphu[$_] eq $v, 0 .. $#graphu;
delete @{ $graph{$u} }[$index];
delete @{ $graph{$v} }[0];
}
else {
push @path, pop(@stack);
}
}
print Dumper \@path;
return @path;
}
`

The error I get is:

` Use of uninitialized value in hash element at euler.pl line 54
`

I expect it to return the output like this:

` $VAR = [5, 4, 3, 5, 2, 3, 1, 2, 4];
`

Actually I try to mimic the working code in Python:

` def eulerPath(graph):
# counting the number of vertices with odd degree
odd = [ x for x in graph.keys() if len(graph[x])&1 ]
print odd
odd.append( graph.keys()[0] )
if len(odd)>3:
return None
stack = [ odd[0] ]
path = []
# main algorithm
while stack:
v = stack[-1]
if graph[v]:
u = graph[v][0]
stack.append(u)
# deleting edge u-v
#print graph[u][ graph[u].index(v) ]
#print graph[u].index(v)
del graph[u][ graph[u].index(v) ]
del graph[v][0]
else:
path.append( stack.pop() )
return path
stack_ = eulerPath({ 1:[2,3], 2:[1,3,4,5], 3:[1,2,4,5], 4:[2,3,5],
+ 5:[2,3,4] })
print stack_
`

---

*neversaint and everlastingly indebted.......*

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