Updated 30 Apr Linked List and Arraylist Java311

8/16/2019 Updated 30 Apr Linked List and Arraylist Java311

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Data Structures

Chapter 12


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Chapter ContentsChapter Objectives12.1 Introductory Example: Countin Internet !ddresses12.2 "he ArrayList and LinkedList Classes

12.# Example: ! Stack !pplication and Class12.$ Example: ! Queue Class12.% !n Introduction to "rees&art o' the &icture: Data Structures

12.( )raphical*Internet +ava: ! PolygonSketcher Class


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Chapter Objectives

Study the +ava collection classes, ArrayList and LinkedList

Sho- ho- to build collection classesStudy the stac and /ueue structures0earn about lin ed structures

lin ed lists and binary treesImplement and use lin ed structuresDiscover ho- collection classes are used

in raphical pro rammin


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evie- !rrays

!n array stores a se/uence o' valuestype [] anArray = new type [ capacity ];

Dra-bac : – capacity o' array 'ixed – must no- max number o' values at compile

time – either the pro ram runs out o' space or-astes spaceSolution: collection classes –

capacity can ro- and shrin as pro ram runs


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12.2 "he ArrayList andLinkedList ClassesCollection classes provide capability to

ro- and shrin as needed

Cate ories o' collection classes – 0ists: store collection o' items, some o'-hich may be the same

– Sets: store collection o' items -ith noduplicates

– aps: store collections o' pairs, eachassociates a .ey -ith an object

3ote List methods, table 12.1


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ArrayList ClassImplements the 0ist usin an array – by usin an Object array, can store any

re'erence type –

cannot directly store primitive types – can indirectly store such values by usininstances o' their -rapper types

Consider the declaration: ArrayList addressSe uence = newArrayList!"; AddressSe eunce

si#e array

0


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The List Interface and ArrayListClass (continued)The List Interface and ArrayListClass (continued)


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The ArrayList ClassThe ArrayList Class

Simplest class that implements the 0ist inter'aceImprovement over an array object4sed -hen a pro rammer -ants to add ne- elements tothe end o' a list but still needs the capability to access

the elements stored in the list in arbitrary order

Simplest class that implements the 0ist inter'aceImprovement over an array object4sed -hen a pro rammer -ants to add ne- elements tothe end o' a list but still needs the capability to access

the elements stored in the list in arbitrary order


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Performance of KWArrayList andthe Vector ClassPerformance of KWArrayList andthe Vector Class

Set and et methods execute in constant timeInsertin or removin elements is linear timeInitial release o' +ava !&I contained the 5ector class-hich has similar 'unctionality to the !rray0ist

6oth contain the same methods3e- applications should use !rray0ist rather than5ectorStac is a subclass o' 5ector

Set and et methods execute in constant timeInsertin or removin elements is linear timeInitial release o' +ava !&I contained the 5ector class-hich has similar 'unctionality to the !rray0ist

6oth contain the same methods3e- applications should use !rray0ist rather than5ectorStac is a subclass o' 5ector


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!ddin to addressSe uence

"he commandaddressSe uence$add!anAddress%ounter"; – appends an!ddressCounter object to the

se/uence"he system -ill then 7

AddressSe eunce si#e array

0

[0] [1] [2] . . . [m-1]

128.159.4.201

Allocate the arrayMake first element

point to the Address%ounter

1

Up ate si!eattri"#te of the

ArrayList


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4pdatin addressSe uence

Consider the command!!Address%ounter"addressSe uence$get!inde&""$incre'ent%ount!";(( assu'e inde& == )


2

[0] [1] [2] . . . [m-1]

128.159.4.2011$ 1 12%.111.222.%%%$ 1

&ets this o"'ect(ast it as an Address%ounter

o"'ect

12%.111.222.%%%$2

)ncrement the countattri"#te


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12%.111.%45.444$ 1

Enlar in the AddressSe uence !rray

8hen allocated array is 'ull, addinanother element 'orces replacin array-ith lar er one – ne- array o' n 9 m allocated – values 'rom old array copied into ne- array – old array replaced by ne- one


2

[0] [1] [2] . . . [ n -1]

128.159.4.2011$ 1 12%.111.222.%%%$ 1


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ArrayList Dra-bac

&roblems arise 'rom usin an array – values can be added only at bac o' ArrayList

– to insert a value and shi't others a'ter itre/uires extensive copyin o' values

– similarly, deletin a value re/uires shi'tin

8e need a sli htly di''erent structure toallo- simple insertions and deletions – the LinkedList class -ill accomplish this


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"he LinkedList Class

)ivenLinkedList alist = new LinkedList!";$ $ $aList$add!new!integer!**"";aList$add!new!integer!++"";aList$add!new!integer!,,"";

esultin objectsho-n at le't

esultin objectsho-n at le't

aList

head si#e tail

%

**88 ++


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0in ed 0ist Containers

aList

head si#e tail

%

**88 ++

3odes:• Contain # handles

• lin to next node

• lin to previous node• lin to stored object

• 0in s to next andprevious ma e it adoubly lin ed list

3odes:• Contain # handles

• lin to next node•

lin to previous node• lin to stored object• 0in s to next and

previous ma e it adoubly lin ed list

!ttributes:•

lin to 'irst item in the list• si;e o' the list• lin to last item in the list

!ttributes:•

lin to 'irst item in the list• si;e o' the list• lin to last item in the list


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5ariations on 0in ed 0ists

0ists can be lin ed doubly as sho-n0ists can also be lin ed in one directiononly – attribute -ould not need lin to tail – node needs 'or-ard lin and pointer to data

only – last item in list has lin set to null0ists can be circularly lin ed – last node has lin to 'irst node


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4sin a LinkedList

)iven the commandLinkedList addressSe uence = new LinkedList!";

4ses the LinkedList constructor tobuild an empty list

head si#e tail

0

addressSe uence


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!ddin to the 0in ed 0ist

esults o' command 'or 'irst addaddressSe uence$add!anAddress%ounter";

head si#e tail

0

addressSe uence

12%.111.%45.444$ 1

• Successive adds• create more nodes

and data values•

adjust lin s


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!ccessin 5alues in a 0in ed 0ist

ust use the $get method!!Address%ounter" addresssSe uence$get!inde&""$incre'ent%ount!";

! LinkedList has no array -ith an indexto access an elementet method must 7

–

be in athead

node – iterate throu h inde& nodes to 'ind match – return re'erence o' object in that nodeCommand then does cast andincre'ent%ount!"


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"o print successive values 'or the output-or !int i = .; i / addressSe uence$si#e!"; i00"Syste'$out$println!addressSe uence$get!i"";

si#e methoetermines limit of loop

co#nter

get!i" starts atfirst no e$ iterates

i times to reachesire no e

• 3ote that each get!i" must pass over thesame 'irst i1) nodes previously accessed

• "his is ine''icient


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!n alternative, more e''icient access al orithmList2terator it =

addressSe uence$list2terator!"; while !it$has3e&t!""

Syste'$out$println! it$ne&t!"";! List2terator is an object that iteratesacross the values in a list"he ne&t!" method does the 'ollo-in :

1. save handle to current node


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Insertin 3odes !ny-here in a0in ed 0ist

ecall problem -ith ArrayList – can add only at end o' the list – lin ed list has capability to insert nodes any-here

8e can sayaddressSe uence$add!n4 new anAddress%ounter";8hich -ill 7 – build a ne- node – update head and tail lin s i' re/uired – update node handle lin s to place ne- node to be n th

item in the list – allocates memory 'or the data item


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Choosin the &roper 0ist!l orithm E''iciency

"ime=e''iciency is not a real=time issue – rather an issue o' ho- many steps an

al orithm re/uires0inear time – time proportional to n – re'erred to as O>n?, order n

Constant time – expressed as O>1?


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Conclusions on E''iciency

I' problem involves many accesses tointerior o' a se/uence – se/uence should be stored in an ArrayListI' problems involves many insertions,deletions not at end – se/uence should be stored in LinkedListI' neither o' these is the case – it doesn


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3eed 'or a Stac

"he remainders are enerated in theopposite order that they must be outputI' -e -ere able to 7 – enerate them – hold on to them as enerated – access >display? them in the

reverse order "AE3 -e have used a stac

+

%

1

1 % +


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Implementin a Stack Class

3ote use o' Stack class in source code,@i ure 12.(, implementation in @i ure 12.B

Implemented -ith 0in ed0ist attributevariable to store values – this is a has=a relationship, the Stack

has a LinkedList – contrast the is=a relationship


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+ava


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12.$ Example: 6uildin a QueueClass

In a /ueue, – ne- values are al-ays added at the 'ront or

head o' the list – values are removed 'rom the opposite end o'the list, the rear or tailExamples o' /ueues – chec out at supermar et – vehicles at toll booth – tic et line at moviesueue exhibits @irst=In=@irst=Out

behavior


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ueues in a Computer System

8hen a process >pro ram? re/uires acertain resource – printer – dis access on a net-or – characters in a eyboard bu''erueue anipulation Operations

– is6'pty!" : returns true or -alse – -irst!" : returns copy o' value at 'ront – add!7" : adds a ne- value at rear o' /ueue – re'o7e!" : removes, returns value at 'ront


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Implementin a Queue Class

Implement as a LinkedList attributevalue – insertions and deletions 'rom either end are

e''icient, occur in constant O>1? time – ood choiceImplement as an ArrayList attribute – poor choice – addin values at one end, removin at other

end re/uire multiple shi'ts


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Implementin a Queue Class

6uild a Queue 'rom scratch – build a lin ed structure to store the /ueue

elements!ttributes re/uired – handle 'or the head node – handle 'or tail node – inte er to store number o' values in the

/ueue – use SinglyLinked3ode class, source code,

@i ure 12.


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Queue Structure

'y9ead 'ySi#e 'y5ail

n

aQueue

. . .

. . .,al#e 0 ,al#e 1 ,al#e n-1


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Queue Class ethods

Constructor – set 'y9ead , 'y5ail to null – set 'ySi#e to ;erois6'pty!" – return results o' comparison 'ySi#e == .-ront!" – return 'y9ead$get8alue!" ** unless empty


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Queue Class ethods

add!" – create ne- node, update attribute variables – i' /ueue is empty, must also update 'y9ead re'o7e!" – must chec i' class not empty

other-ise 7 – save handle to 'irst object – adjust head to re'er to node – update 'ySi#e ote so#rce co e for

hole class$ /i #re 12.9

ote so#rce co e for

hole class$ /i #re 12.9


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12.% !n Introduction to "rees

8e see a -ay to or ani;ed a lin edstructure so that 7 – elements can be searched more /uic ly than

in a linearly lin ed structure – also provide 'or easy insertion*deletion – permit access in less than O>n? timeecall binary search strate y

– loo in middle o' list – eep loo in in middle o' subset above or

belo- current location in list –

until tar et value 'ound


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5isuali;e 6inary Search

1% 28 %5 49 *2 ** 80

ra n as a binary tree

4928

1% %5

**

*2 80


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"ree "erminolo y

! tree consists o': – 'inite collection o' nodes – non empty tree has a root node – root node has no incomin lin s – every other node in the tree can be reached 'rom

the root by uni/ue se/uence o' lin s

4928

1% %5

**

*2 80

eaf no es

3i"lin no esarent

an

chil no es


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!pplications o' "rees

)enealo ical tree – pictures a person


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Examples o' 6inary "rees

Each node has at most t-o children4se'ul in modelin processes -here atest has only t-o possible outcomes – true or 'alse – coin toss, heads or tailsEach uni/ue path can be described by these/uence o' outcomesCan be applied to decision trees in expertsystems o' arti'icial intelli ence


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Implementin 6inary "rees

6inary tree represented by multiplylin ed structure – each node has t-o lin s and a handle to the

data – one lin to le't child, other to the ri ht

8alue

'y8alue

'y:ight%hild 'yLe-t%hild


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Declaration o' inary5ree3ode class

public class inary5ree3ode

<(( 'ethods go here(( Attributes

pri7ate inary5ree3ode 'yLe-t%hild4 'y:ight%hild;

pri7ate Object 'y8alue;>

ointers tos#ccee in no es

an le to store ,al#e


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inary5ree3ode is only one o' theattributes o' a inary5ree class!lso need an attribute that eeps trac o'the number o' nodes in the tree

public class inary5ree e&tends Object<(( 'ethods

pri7ate inary5ree3ode 'y:oot; pri7ate int 'ySi#e;

>


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5isuali;in a 6inary"ree

4*

*%1+

%

'y:oot 'ySi#e

a 5ree


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6inary Search "rees

Search !l orithm1. Initiali;e a handle current3ode to the

node containin the root2. epeatedly do the 'ollo-in :

I' tar etGitem H current3ode.my5alue set current3ode current3ode.le'tChild

I' tar etGitem 9 current3ode.my5alueset current3ode current3ode.ri htChildElse

terminate repetition because tar etGitemhas been 'ound


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"ree "raversals

! traversal is movin throu h the binary tree,visitin each node exactly once

– 'or no- order not important

"raverse !l orithm1. 5isit the root and process its contents2. "raverse the le't subtree

1. visit its root, process

2. traverse le't sub=sub tree#. traverse ri ht sub=sub tree#. "raverse the ri ht subtree

1. 7


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"ree "raversal is ecursive

I' the binary tree is empty thendo nothin

Else0: "raverse the le't subtree3: 5isit the root

: "raverse the ri ht subtree

6he 7anchor7

6he in #cti,e step


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"raversal Order

"hree possibilities 'or inductive step 70e't subtree, 3ode, i ht subtreethe inorder traversal

3ode, 0e't subtree, i ht subtreethe preorder traversal

0e't subtree, i ht subtree, 3odethe postorder traversal


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Constructin 6inary Search"rees

epeatedly insert elements into a 6S" that isinitially emptyDescend tree, loo in 'or place to insert the

item – Set parent3ode = current3ode – chan e current3ode to its le't or ri ht child – i' value bein inserted is not in the tree,

current3ode -ill eventually become null and 7 – parent3ode -ill indicate the parent o' a ne- node

to contain the value


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&art o' the &icture:Data Structures+ava provides standard classes – !rray0ist – 0in ed0istStandard classes used to solve variety o'problems8ise use o' these data structures simplysolutions to many problems!ttention should be iven to e''iciencyo' structure 'or particular tas at hand


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Other Data Structures

Set inter'ace implemented by 9ashSet and 5reeSet classes

?ap inter'ace implemented by 5ree?ap and 9ash5able classes

%ollections class – variety o' utility methods 'or manipulatin

collections

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Updated 30 Apr Linked List and Arraylist Java311

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