<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
a	O
linked	B-Application
data	I-Application
structure	I-Application
is	O
a	O
data	B-General_Concept
structure	I-General_Concept
which	O
consists	O
of	O
a	O
set	O
of	O
data	O
records	O
(	O
nodes	B-Data_Structure
)	O
linked	O
together	O
and	O
organized	O
by	O
references	O
(	O
links	O
or	O
pointers	O
)	O
.	O
</s>
<s>
The	O
link	O
between	O
data	O
can	O
also	O
be	O
called	O
a	O
connector	B-Application
.	O
</s>
<s>
In	O
linked	B-Application
data	I-Application
structures	I-Application
,	O
the	O
links	O
are	O
usually	O
treated	O
as	O
special	O
data	O
types	O
that	O
can	O
only	O
be	O
dereferenced	O
or	O
compared	O
for	O
equality	O
.	O
</s>
<s>
Linked	B-Application
data	I-Application
structures	I-Application
are	O
thus	O
contrasted	O
with	O
arrays	B-Data_Structure
and	O
other	O
data	B-General_Concept
structures	I-General_Concept
that	O
require	O
performing	O
arithmetic	O
operations	O
on	O
pointers	O
.	O
</s>
<s>
This	O
distinction	O
holds	O
even	O
when	O
the	O
nodes	B-Data_Structure
are	O
actually	O
implemented	O
as	O
elements	O
of	O
a	O
single	O
array	O
,	O
and	O
the	O
references	O
are	O
actually	O
array	O
indices	B-Data_Structure
:	O
as	O
long	O
as	O
no	O
arithmetic	O
is	O
done	O
on	O
those	O
indices	B-Data_Structure
,	O
the	O
data	B-General_Concept
structure	I-General_Concept
is	O
essentially	O
a	O
linked	O
one	O
.	O
</s>
<s>
Linked	B-Application
data	I-Application
structures	I-Application
include	O
linked	B-Data_Structure
lists	I-Data_Structure
,	O
search	B-Data_Structure
trees	I-Data_Structure
,	O
expression	B-Algorithm
trees	I-Algorithm
,	O
and	O
many	O
other	O
widely	O
used	O
data	B-General_Concept
structures	I-General_Concept
.	O
</s>
<s>
They	O
are	O
also	O
key	O
building	O
blocks	O
for	O
many	O
efficient	O
algorithms	O
,	O
such	O
as	O
topological	B-Algorithm
sort	I-Algorithm
and	O
set	B-Algorithm
union-find	I-Algorithm
.	O
</s>
<s>
A	O
linked	B-Data_Structure
list	I-Data_Structure
is	O
a	O
collection	O
of	O
structures	O
ordered	O
not	O
by	O
their	O
physical	O
placement	O
in	O
memory	O
but	O
by	O
logical	O
links	O
that	O
are	O
stored	O
as	O
part	O
of	O
the	O
data	O
in	O
the	O
structure	O
itself	O
.	O
</s>
<s>
Linked	B-Data_Structure
list	I-Data_Structure
can	O
be	O
singly	O
,	O
doubly	O
or	O
multiply	O
linked	O
and	O
can	O
either	O
be	O
linear	O
or	O
circular	O
.	O
</s>
<s>
Objects	O
,	O
called	O
nodes	B-Data_Structure
,	O
are	O
linked	O
in	O
a	O
linear	O
sequence	O
.	O
</s>
<s>
This	O
is	O
an	O
example	O
of	O
the	O
node	O
class	O
used	O
to	O
store	O
integers	O
in	O
a	O
Java	O
implementation	O
of	O
a	O
linked	B-Data_Structure
list	I-Data_Structure
:	O
</s>
<s>
This	O
is	O
an	O
example	O
of	O
the	O
structure	O
used	O
for	O
implementation	O
of	O
linked	B-Data_Structure
list	I-Data_Structure
in	O
C	O
:	O
</s>
<s>
This	O
is	O
an	O
example	O
using	O
typedefs	B-Language
:	O
</s>
<s>
This	O
is	O
an	O
example	O
of	O
the	O
node	O
class	O
structure	O
used	O
for	O
implementation	O
of	O
linked	B-Data_Structure
list	I-Data_Structure
in	O
C++	O
:	O
</s>
<s>
A	O
search	B-Data_Structure
tree	I-Data_Structure
is	O
a	O
tree	O
data	B-General_Concept
structure	I-General_Concept
in	O
whose	O
nodes	B-Data_Structure
data	O
values	O
can	O
be	O
stored	O
from	O
some	O
ordered	O
set	O
,	O
which	O
is	O
such	O
that	O
in	O
an	O
in-order	O
traversal	O
of	O
the	O
tree	O
the	O
nodes	B-Data_Structure
are	O
visited	O
in	O
ascending	O
order	O
of	O
the	O
stored	O
values	O
.	O
</s>
<s>
Objects	O
,	O
called	O
nodes	B-Data_Structure
,	O
are	O
stored	O
in	O
an	O
ordered	O
set	O
.	O
</s>
<s>
Compared	O
to	O
arrays	B-Data_Structure
,	O
linked	B-Application
data	I-Application
structures	I-Application
allow	O
more	O
flexibility	O
in	O
organizing	O
the	O
data	O
and	O
in	O
allocating	O
space	O
for	O
it	O
.	O
</s>
<s>
In	O
arrays	B-Data_Structure
,	O
the	O
size	O
of	O
the	O
array	O
must	O
be	O
specified	O
precisely	O
at	O
the	O
beginning	O
,	O
which	O
can	O
be	O
a	O
potential	O
waste	O
of	O
memory	O
,	O
or	O
an	O
arbitrary	O
limitation	O
which	O
would	O
later	O
hinder	O
functionality	O
in	O
some	O
way	O
.	O
</s>
<s>
A	O
linked	B-Application
data	I-Application
structure	I-Application
is	O
built	O
dynamically	O
and	O
never	O
needs	O
to	O
be	O
bigger	O
than	O
the	O
program	O
requires	O
.	O
</s>
<s>
In	O
an	O
array	O
,	O
the	O
array	B-Data_Structure
elements	I-Data_Structure
have	O
to	O
be	O
in	O
a	O
contiguous	O
(	O
connected	O
and	O
sequential	O
)	O
portion	O
of	O
memory	O
.	O
</s>
<s>
But	O
in	O
a	O
linked	B-Application
data	I-Application
structure	I-Application
,	O
the	O
reference	O
to	O
each	O
node	O
gives	O
users	O
the	O
information	O
needed	O
to	O
find	O
the	O
next	O
one	O
.	O
</s>
<s>
The	O
nodes	B-Data_Structure
of	O
a	O
linked	B-Application
data	I-Application
structure	I-Application
can	O
also	O
be	O
moved	O
individually	O
to	O
different	O
locations	O
within	O
physical	O
memory	O
without	O
affecting	O
the	O
logical	O
connections	O
between	O
them	O
,	O
unlike	O
arrays	B-Data_Structure
.	O
</s>
<s>
With	O
due	O
care	O
,	O
a	O
certain	O
process	B-Operating_System
or	O
thread	B-Operating_System
can	O
add	O
or	O
delete	O
nodes	B-Data_Structure
in	O
one	O
part	O
of	O
a	O
data	B-General_Concept
structure	I-General_Concept
even	O
while	O
other	O
processes	O
or	O
threads	B-Operating_System
are	O
working	O
on	O
other	O
parts	O
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
access	O
to	O
any	O
particular	O
node	O
in	O
a	O
linked	B-Application
data	I-Application
structure	I-Application
requires	O
following	O
a	O
chain	O
of	O
references	O
that	O
are	O
stored	O
in	O
each	O
node	O
.	O
</s>
<s>
If	O
the	O
structure	O
has	O
n	O
nodes	B-Data_Structure
,	O
and	O
each	O
node	O
contains	O
at	O
most	O
b	O
links	O
,	O
there	O
will	O
be	O
some	O
nodes	B-Data_Structure
that	O
cannot	O
be	O
reached	O
in	O
less	O
than	O
logb	O
n	O
steps	O
,	O
slowing	O
down	O
the	O
process	B-Operating_System
of	O
accessing	O
these	O
nodes	B-Data_Structure
-	O
this	O
sometimes	O
represents	O
a	O
considerable	O
slowdown	O
,	O
especially	O
in	O
the	O
case	O
of	O
structures	O
containing	O
large	O
numbers	O
of	O
nodes	B-Data_Structure
.	O
</s>
<s>
For	O
many	O
structures	O
,	O
some	O
nodes	B-Data_Structure
may	O
require	O
worst	B-General_Concept
case	I-General_Concept
up	O
to	O
n1	O
steps	O
.	O
</s>
<s>
In	O
contrast	O
,	O
many	O
array	B-Data_Structure
data	I-Data_Structure
structures	I-Data_Structure
allow	O
access	O
to	O
any	O
element	O
with	O
a	O
constant	O
number	O
of	O
operations	O
,	O
independent	O
of	O
the	O
number	O
of	O
entries	O
.	O
</s>
<s>
Broadly	O
the	O
implementation	O
of	O
these	O
linked	B-Application
data	I-Application
structure	I-Application
is	O
through	O
dynamic	B-Data_Structure
data	I-Data_Structure
structures	I-Data_Structure
.	O
</s>
<s>
Memory	O
can	O
be	O
utilized	O
more	O
efficiently	O
by	O
using	O
these	O
data	B-General_Concept
structures	I-General_Concept
.	O
</s>
<s>
Memory	O
is	O
allocated	O
as	O
per	O
the	O
need	O
and	O
when	O
memory	O
is	O
not	O
further	O
needed	O
,	O
deallocation	B-General_Concept
is	O
done	O
.	O
</s>
<s>
Linked	B-Application
data	I-Application
structures	I-Application
may	O
also	O
incur	O
in	O
substantial	O
memory	B-General_Concept
allocation	I-General_Concept
overhead	O
(	O
if	O
nodes	B-Data_Structure
are	O
allocated	O
individually	O
)	O
and	O
frustrate	O
memory	B-Architecture
paging	I-Architecture
and	O
processor	B-General_Concept
caching	I-General_Concept
algorithms	O
(	O
since	O
they	O
generally	O
have	O
poor	O
locality	B-General_Concept
of	I-General_Concept
reference	I-General_Concept
)	O
.	O
</s>
<s>
In	O
some	O
cases	O
,	O
linked	B-Application
data	I-Application
structures	I-Application
may	O
also	O
use	O
more	O
memory	O
(	O
for	O
the	O
link	O
fields	O
)	O
than	O
competing	O
array	O
structures	O
.	O
</s>
<s>
This	O
is	O
because	O
linked	B-Application
data	I-Application
structures	I-Application
are	O
not	O
contiguous	O
.	O
</s>
<s>
Instances	O
of	O
data	O
can	O
be	O
found	O
all	O
over	O
in	O
memory	O
,	O
unlike	O
arrays	B-Data_Structure
.	O
</s>
<s>
In	O
arrays	B-Data_Structure
,	O
nth	O
element	O
can	O
be	O
accessed	O
immediately	O
,	O
while	O
in	O
a	O
linked	B-Application
data	I-Application
structure	I-Application
we	O
have	O
to	O
follow	O
multiple	O
pointers	O
so	O
element	O
access	O
time	O
varies	O
according	O
to	O
where	O
in	O
the	O
structure	O
the	O
element	O
is	O
.	O
</s>
<s>
In	O
some	O
theoretical	O
models	O
of	O
computation	O
that	O
enforce	O
the	O
constraints	O
of	O
linked	O
structures	O
,	O
such	O
as	O
the	O
pointer	B-Application
machine	I-Application
,	O
many	O
problems	O
require	O
more	O
steps	O
than	O
in	O
the	O
unconstrained	O
random	B-Application
access	I-Application
machine	I-Application
model	O
.	O
</s>
