<s>
The	O
quartet	B-Algorithm
distance	I-Algorithm
is	O
a	O
way	O
of	O
measuring	O
the	O
distance	O
between	O
two	O
phylogenetic	O
trees	O
.	O
</s>
<s>
It	O
is	O
defined	O
as	O
the	O
number	O
of	O
subsets	O
of	O
four	O
leaves	O
that	O
are	O
not	O
related	O
by	O
the	O
same	O
topology	B-Architecture
in	O
both	O
trees	O
.	O
</s>
<s>
The	O
most	O
straightforward	O
computation	O
of	O
the	O
quartet	B-Algorithm
distance	I-Algorithm
would	O
require	O
time	O
,	O
where	O
is	O
the	O
number	O
of	O
leaves	O
in	O
the	O
trees	O
.	O
</s>
<s>
found	O
an	O
algorithm	O
that	O
takes	O
time	O
to	O
compute	O
the	O
quartet	B-Algorithm
distance	I-Algorithm
between	O
two	O
multifurcating	O
trees	O
when	O
is	O
the	O
maximum	O
degree	O
of	O
the	O
trees	O
,	O
which	O
is	O
in	O
C	O
,	O
perl	O
,	O
and	O
the	O
R	B-Language
package	O
.	O
</s>
