Download implementations of SortedMap

CS2230
CSII:Datastructures
Meeting28:SortedListMap
BrandonMyers
UniversityofIowa
Today’sbigideas
• SortedMap isanextensionofMapthatincludesadditional
methodsthatdependonkeyshavinganordering
• TwoapproachestoimplementingSortedMap arewith
sortedlistsorsearchtrees;we’lllookatSortedListMap
Helpfultohavethecodeinfrontofyoutoday:Goto4/3lecture
materialsonthewebsitetoaccesstheJavacode
DictionaryApp.java
Input:Textfilewith”WORD”:”definition”
{"DIPLOBLASTIC":"Characterizing theovumwhenithastwoprimary
germinallayers.",
"DEFIGURE":"To delineate.[Obs.]Thesetwostonesastheyareheredefigured.
Weever.",
"LOMBARD":"Of orpertainingtoLombardy,ortheinhabitantsofLombardy.",
"BAHAISM":"The religioustenetsorpracticesoftheBahais.",
"FUMERELL":"See Femerell.",
"ROYALET":"Apettyorpowerlessking.[R.]therewereatthistimetwoother
royalets,asonlykingsbyhisleave.Fuller.",
"TROPHIED":"Adorned withtrophies.The trophied arches,storiedhalls,invade.
Pope.",...}
illustrationofaSortedMap
put(word,def)
into
SortedMap
querythe
SortedMap,e.g.,
firstEntry()
A
Thefirstletterofthe
English...
key
value
A
ThefirstletteroftheEnglish...
ACHEVAL
Astride;withapartoneachside...
AFORTIORI
Withstrongerreason.
...
...
ZYTHEPSARY
Abrewery.
SortedMap.java
Thisinterfaceextends Map,soaSortedMap cando
everythingaMapcando
get, put, remove, ...
inadditiontomethodsthattakeadvantageofsome
orderingontheKeys
SortedMap classhierarchy
Map
SortedMap
AbstractSort
AbstractMap
edMap
HashMap
BSTMap
aka,AVLTreeMap
UnsortedListMap
SortedListMap
AbstractSortedMap.java
Providesmethods/constructorsthatareprobably
usefulformanyimplementationsofSortedMap
protected AbstractSortedMap(Comparator<K> c) {
comp = c;
TheComparator<K>interface
}
providesthe
int compare(K o1, K o2) method
/** Initializes the map with a default comparator. */
protected AbstractSortedMap() {
// default comparator uses natural ordering
this(new DefaultComparator<K>());
}
Anorderingonthekeysneedstobedefined.AbstractSortedMap
providestwoconstructorsthatallowyoutodefinethatordering.
SortedMap classhierarchy
Map
SortedMap
AbstractSort
AbstractMap
edMap
HashMap
BSTMap
aka,AVLTreeMap
UnsortedListMap
SortedListMap
SortedListMap<Integer,String>
entries
ArrayList<MapEntry<Integer,String>>
elements
count
2
MapEntry<Integer, String>
k
"A"
v
"The first letter ..."
MapEntry<Integer, String>
k
"A CHEVAL"
v
"Astride; with a..."
Peerinstruction
https://b.socrative.com/login/student/
CS2230Aids1000-4999
CS2230Bids5000+
Whatrunningtimeshouldweaimforfor
SortedListMap.get()?
a)
b)
c)
d)
e)
O(1)
O(logn)
O(n)
O(nlogn)
O(n^2)
BONUS:runningtimefor...
put
ceiling(key)
floor(key)
higherEntry(key)
lastEntry()
IteratingthroughtheresultofsubMap
SortedListMap.java
• put(k,v)
• step1:findtheindex,j,wherekwouldgoinsorted
order
• step2:
• ifentries[j]alreadyholdsthekeyk,thenoverwritethevalueof
thatentrywithv
• otherwise,addanewentry(k,v)atindexj.TheArrayList.add
methodmustcopyeverythingaftertheinsertionpoint!
• runningtime
• step1:O(logn)withbinarysearch
• step2:O(1)inthefirstcase,O(n)todothecopyinthesecond
case;thereforeworstcaseO(n)
• thereforeputisworstcaseO(n)
SortedListMap.java
• higherEntry(k)
• step1:findtheindex,j,wherekwouldgoinsorted
order
• step2:
• ifentries[j]holdsthekeyk,thenreturnentries[j+1]ifitexists
• otherwise,returnentries[j],whichmusthavealargerkeythan
k
• runningtime
• step1:O(logn)withbinarysearch
• step2:O(1)inbothcases
• thereforehigherEntryisO(logn)
SortedListMap.java
subMap(“Do”,“Egg”)returnsasnapshotiterable
MapEntry<Integer, String>
"A"
MapEntry<Integer, String>
"The first letter ..."
k
v
Currentindex
buffer
0
"Door"
"A covering for..."
MapEntry<Integer, String>
k
v
"Dog"
"A life form..."
MapEntry<Integer, String>
MapEntry<Integer, String>
k
"Turtle"
k
v
"A shelled..."
v
"Zebra"
"Known to have..."
Copytheportionofthearraywherethekeys
fallinrange“Do”to“Egg”into abuffer(the“snapshot”)
Why?ourcopywillbesafe.Removesremovesonthe
map
thatoccurbeforewereturnallelementsfromthe
iteratorwon’taffecttheiterator
(however,sincewecopiedonlyreferences,puts that
overwriteentrieswill beseen)
SortedListMap.java
subMap runtime?
Let’sassumen=numberofentriesands=numberof
entriesreturnedinthesubMap.
• 𝑂(log𝑛)tofindthestartkeyusingbinarysearch
• 𝑂(𝑠)toiteratefromthestartkeytothefirstkey
thatistoobig
therefore,subMap is𝑂(𝑠 + 𝑙𝑜𝑔𝑛)
Administrivia
HW7out,dueon4/13
SeeannouncementonICONforsigningupHW8
partners(pairprogrammingproject)
UsingversioncontrolinHW8
Git
Youwillgetexperienceinmanagingversionsofyour
codeandsharingyourcodewithapartnerinHW8.
Nextweek’sdiscussion(4/10-4/12)isacrashcourse
ongit.Bringyourlaptopwithgit readytogo!
(instructionsforthcomingonICON)
Today’sbigideas
• SortedMap isanextensionofMapthatincludesadditional
methodsthatdependonkeyshavinganordering
• TwoapproachestoimplementingSortedMap arewith
sortedlistsorsearchtrees;we’lllookatSortedListMap
Helpfultohavethecodeinfrontofyoutoday:Goto4/3lecture
materialsonthewebsitetoaccesstheJavacode
resources
• Forananimationofbinarysearchsee
http://www.cs.usfca.edu/~galles/visualization/Sear
ch.html