<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
Tarjan	B-Algorithm
's	I-Algorithm
off-line	I-Algorithm
lowest	I-Algorithm
common	I-Algorithm
ancestors	I-Algorithm
algorithm	I-Algorithm
is	O
an	O
algorithm	O
for	O
computing	O
lowest	O
common	O
ancestors	O
for	O
pairs	O
of	O
nodes	O
in	O
a	O
tree	O
,	O
based	O
on	O
the	O
union-find	B-Algorithm
data	I-Algorithm
structure	I-Algorithm
.	O
</s>
<s>
The	O
simplest	O
version	O
of	O
the	O
algorithm	O
uses	O
the	O
union-find	B-Algorithm
data	I-Algorithm
structure	I-Algorithm
,	O
which	O
unlike	O
other	O
lowest	O
common	O
ancestor	O
data	O
structures	O
can	O
take	O
more	O
than	O
constant	O
time	O
per	O
operation	O
when	O
the	O
number	O
of	O
pairs	O
of	O
nodes	O
is	O
similar	O
in	O
magnitude	O
to	O
the	O
number	O
of	O
nodes	O
.	O
</s>
