Data Structures and Algorithms with Scala: A Practitioner's Approach with Emphasis on Functional Programming

164 Pages·2019·1.36 MB·English

by  Bhim P. Upadhyaya

Undergraduate Topics in Computer Science
Bhim P. Upadhyaya
Data
Structures and
Algorithms
with Scala
A Practitioner’s Approach with
Emphasis on Functional Programming
Undergraduate Topics in Computer Science
Series editor
Ian Mackie
Advisory Board
Samson Abramsky, University of Oxford, Oxford, UK
Chris Hankin, Imperial College London, London, UK
Mike Hinchey, University of Limerick, Limerick, Ireland
Dexter C. Kozen, Cornell University, Ithaca, USA
Andrew Pitts, University of Cambridge, Cambridge, UK
HanneRiisNielson,TechnicalUniversityofDenmark,KongensLyngby,Denmark
Steven S. Skiena, Stony Brook University, Stony Brook, USA
Iain Stewart, University of Durham, Durham, UK
Undergraduate Topics in Computer Science (UTiCS) delivers high-quality
instructional content for undergraduates studying in all areas of computing and
information science. From core foundational and theoretical material to final-year
topics and applications, UTiCS books take a fresh, concise, and modern approach
and are ideal for self-study or for a one- or two-semester course. The texts are all
authoredbyestablishedexpertsintheirfields,reviewedbyaninternationaladvisory
board, and contain numerous examples and problems. Many include fully worked
solutions.
More information about this series at http://www.springer.com/series/7592
Bhim P. Upadhyaya
Data Structures
and Algorithms with Scala
’
A Practitioner s Approach with Emphasis
on Functional Programming
123
Bhim P.Upadhyaya
EqualInformation, LLC
Sunnyvale,CA,USA
ISSN 1863-7310 ISSN 2197-1781 (electronic)
Undergraduate Topics inComputer Science
ISBN978-3-030-12560-8 ISBN978-3-030-12561-5 (eBook)
https://doi.org/10.1007/978-3-030-12561-5
LibraryofCongressControlNumber:2019930577
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TotheReaders
-Bhim
Preface
Professional software engineers find it difficult to make time to upgrade and rein-
force their own knowledge; most of their time is spent on business responsibili-
ties.Thisisalsotrueforengineeringstudents(amongothers),whohavenumerous
coursestotakeandrigorousexercisestodo.So,timeisaconstraintforalmostev-
erybody.Itisourobservationthatprofessionalsneedconciseinformationsourcein
ordertobeabletoallocateandgetvalueoutoftheirtime.Inthiscontext,itishandy
tohaveabookthatcanbereviewedinoneortwoweekends.
A quick survey of books on Data Structures and Algorithms reveals that there
are plenty of well-written books; however, they have multiple shortcomings. One
that stands out is that most of those books were written a decade back. Computer
scienceisoneofthefastest-ifnotthefastest-changingfields.Thereisasaying:
everytimeyouturnyourheadyoumightseesomethingnew,whichistrue,specially
withtheadvancesinautomatedbuilds.Theremightbethousandsofbuildsrunning
orcompletingatagivenpointintime.Allthesuccessfulbuildscreatenewversions
of existing software packages or new software packages. In this rapidly changing
context,bookswrittenadecadeormoreagomaynotservethepurposebest.
Anothershortcomingofwell-writtenclassicalbooksinthisfieldisthattheyare
eithertoolongortootheoreticalforpractitioners.Findingweeksoffreetimetoread
abookiscertainlychallengingforworkingsoftwareengineers,amidtheirstringent
workresponsibilities.Also,too-theoreticalbooksmightbegoodforintellectualex-
ercisesandresearchinthefield,butmaynotservewelltosolveappliedproblems
quickly.Mostprofessionalengineerslookforterseandprecisepresentationofma-
terial.
ThethirdaspectisthattherearenotmanyDataStructuresandAlgorithmsbooks
available for Scala. Scala is becoming popular in the big data space. Most senior
Java-basedsoftwarejobs,thesedays,preferScalaproficiency.Inthiscontext,itis
certainlyhelpfultobeequippedwithScalaimplementationsofpopulardatastruc-
turesaswellasalgorithms.Mostoftheanalyticaltasksarebetterdonebythefunc-
tional style of processing. As Scala is an object-functional language, we can do
multi-paradigmprogramming.Scalaalsosupportspolyglotprogramming,Javabe-
ingtheclosestsibling.
vii
viii Preface
This book has been written more in a study-note or tutorial style and it covers
ninepopulartopicsinDataStructuresandAlgorithms—arrays,lists,stacks,queues,
hash tables, binary trees, sorting, searching, and graphs. Arrays are implemented
in an imperative style with the famous matrix multiplication problem. Most of the
othertopicsareimplementedinafunctionalstyle.So,ifyouareplanningtolearna
functionalversionofDataStructuresandAlgorithmsinScala,thisistherightbook.
I’vetriedtomakethebookasaccessibleaspossible.
Mostoftheprogramsinthisbookarecompleteandrunningapplications.Also,
each topic or subtopic has at least one complete and running example, which will
save your time. You can try to come up with better implementations than in this
book. Most of the challenge exercises are for this purpose. However, some are in-
tendedtoreinforceyourunderstandingoftheexistingmaterial.Inadditiontocre-
ativity,theabilitytotakesomebodyelse’ssolutionandimproveisdesirableinthe
job market; I’ve tried to incorporate both in this book. Also the book includes so-
lution to exercises so that you don’t struggle, specially when you are time-bound.
HappyReading!
Sunnyvale,California BhimP.Upadhyaya
October2018
Contents
1 FoundationalComponents ...................................... 1
1.1 Arrays.................................................... 2
1.2 ListsandVectors ........................................... 6
1.3 AppliedTechniquesforEfficientComputation .................. 8
1.3.1 LazyEvaluation ..................................... 8
1.3.2 Memoization........................................ 10
1.4 Streams................................................... 11
1.5 SlidingWindows........................................... 16
2 FundamentalAlgorithms ....................................... 19
2.1 PrimeNumbers ............................................ 19
2.2 DecimaltoBinaryConversion................................ 21
2.3 DivideandConquer ........................................ 22
2.4 GreedyAlgorithms ......................................... 25
3 Arrays ........................................................ 27
3.1 Structure.................................................. 28
3.2 TypicalImplementation ..................................... 29
3.3 Analysis .................................................. 32
3.4 Application................................................ 32
4 Lists .......................................................... 35
4.1 Structure.................................................. 36
4.2 TypicalImplementation ..................................... 36
4.3 Analysis .................................................. 40
4.4 Application................................................ 41
5 Stacks ........................................................ 45
5.1 Structure.................................................. 45
5.2 TypicalImplementation ..................................... 45
5.3 Analysis .................................................. 48
ix
x Contents
5.4 Application................................................ 48
6 Queues........................................................ 51
6.1 Structure.................................................. 51
6.2 TypicalImplementation ..................................... 52
6.3 Analysis .................................................. 55
6.4 Application................................................ 56
7 HashTables ................................................... 57
7.1 StructureandAlgorithm..................................... 57
7.2 TypicalImplementation ..................................... 58
7.3 Analysis .................................................. 66
7.4 Application................................................ 66
8 BinaryTrees................................................... 67
8.1 StructureandAlgorithms .................................... 67
8.1.1 Preorder............................................ 68
8.1.2 Inorder............................................. 68
8.1.3 Postorder ........................................... 68
8.2 TypicalImplementation ..................................... 68
8.3 Analysis .................................................. 73
8.4 Application................................................ 73
9 Sorting........................................................ 77
9.1 BubbleSort ............................................... 77
9.1.1 Algorithm .......................................... 77
9.1.2 TypicalImplementation............................... 78
9.2 SelectionSort.............................................. 79
9.2.1 Algorithm .......................................... 79
9.2.2 TypicalImplementation............................... 80
9.3 InsertionSort .............................................. 81
9.3.1 Algorithm .......................................... 81
9.3.2 TypicalImplementation............................... 82
9.4 MergeSort ................................................ 84
9.4.1 Algorithm .......................................... 84
9.4.2 TypicalImplementation............................... 84
9.5 QuickSort ................................................ 87
9.5.1 Algorithm .......................................... 87
9.5.2 TypicalImplementation............................... 87
9.6 ComparativeAnalysis....................................... 89
9.7 Application................................................ 90