<s>
Given	O
two	O
graphs	O
and	O
,	O
the	O
maximum	B-Algorithm
common	I-Algorithm
edge	I-Algorithm
subgraph	I-Algorithm
problem	I-Algorithm
is	O
the	O
problem	O
of	O
finding	O
a	O
graph	O
with	O
as	O
many	O
edges	O
as	O
possible	O
which	O
is	O
isomorphic	O
to	O
both	O
a	O
subgraph	O
of	O
and	O
a	O
subgraph	O
of	O
.	O
</s>
<s>
The	O
maximum	B-Algorithm
common	I-Algorithm
edge	I-Algorithm
subgraph	I-Algorithm
problem	I-Algorithm
on	O
general	O
graphs	O
is	O
NP-complete	O
as	O
it	O
is	O
a	O
generalization	O
of	O
subgraph	O
isomorphism	O
:	O
a	O
graph	O
is	O
isomorphic	O
to	O
a	O
subgraph	O
of	O
another	O
graph	O
if	O
and	O
only	O
if	O
the	O
maximum	B-Algorithm
common	I-Algorithm
edge	I-Algorithm
subgraph	I-Algorithm
of	O
and	O
has	O
the	O
same	O
number	O
of	O
edges	O
as	O
.	O
</s>
<s>
Unless	O
the	O
two	O
inputs	O
and	O
to	O
the	O
maximum	B-Algorithm
common	I-Algorithm
edge	I-Algorithm
subgraph	I-Algorithm
problem	I-Algorithm
are	O
required	O
to	O
have	O
the	O
same	O
number	O
of	O
vertices	O
,	O
the	O
problem	O
is	O
APX-hard	B-Algorithm
.	O
</s>
