welcome to csl 201 – data structurescse.iitrpr.ac.in/ckn/courses/f2015/csl201/w1.pdf ·...

Welcome to CSL 201 – Data Structures

Narayanan (CK) C Krishnan Department of Computer Science and Engineering IIT Ropar

Administrative Trivia q  Course Structure

n  3-0-4 (5 credits)

q  Class Timings n  Monday 9.55-10.45 n  Tuesday 10.50-11.40 n  Wednesday 11.45-12.35

q  Lab hours n  Thursday 9.00-12.35

q  Teaching Assistant n  Yayati Gupta

([email protected])

q  Office Hours n  Instructor – M,T,W

immediately after class n  TA – during lab hours

q  Course Google group – [email protected]

q  Pre-registered students have already been added n  other students – send

email to the instructor

q  Pseudonym n  5 character n  July 31, 5.00pm

2

Reference Material

3

Data Structures and Algorithms in Java Goodrich, Tamasia and Goldwasser 6th edition

Introduction to Algorithms Cormen, Leiserson, Rivest, Stein 3rd edition

Fundamentals of Data Structures Horowitz Sahni

Learning every week

4

Tentative Course Schedule

5

Quizzes – 30% q  Almost every alternate

Thursday n  9.00-10.30am n  L2

q  Q3 and Q6 will also have programming problems

q  Cover material discussed from the previous quiz till the current week

q  Duration – 30-45m q  Rest of the time –

problem solving/tutorial 6

Quiz Number Date

Q1 Aug 6

Q2 Aug 20

Q3 Sep 3

Q4 Oct 1

Q5 Oct 15

Q6 Oct 29

Q7 Nov 12

Labs – 20% q  Due almost every

alternate Friday 11.55pm q  Programming

Assignments q  TA is available for any

assistance. q  Java – programming

language n  Introductory Tutorial -

July 30 9-10.30am in L2

Lab Number Date

L1 Aug 14

L2 Aug 28

L3 Sep 4

L4 Sep 24

L5 Oct 8

L6 Oct 22

L7 Nov 5

L8 Nov 19

7

Grading Scheme q  Tentative Breakup

n  Quizzes (6-7) 30% n  Labs (6-8) – 20% n  Mid-Semester Exam – 25% n  End-Semester Exam – 25%

8

Passing Criteria: A student has to secure an overall score of 40(out of 100) and a combined score of 60(out of 200) in the exams to pass the course

Attendance – Bonus 1% q  No mandatory attendance q  Encourage you to attend classes q  Attendance will be taken during every

class q  1% will count towards the final score

n  Borderline grades will have an edge

9

Honor Code q  Encourage to form study groups to review

class lectures/textbook material n  Group discussions are encouraged

q  Unless explicitly stated all quizzes and labs n  are to be done individually. n  web trawled code or code copied from classmates

is strictly forbidden.

q  Any infraction will be dealt in severest terms n  Direct ‘F’ grade in the course.

10

I reserve the right to question you, if I suspect any misconduct in any submission.

Course Website q  http://cse.iitrpr.ac.in/ckn/courses/f2015/

csl201/csl201.html

q  All class related material will be accessible from the course webpage.

11

Data Structures q  What are data structures?

12

Data Structures q  What are data structures?

n  a way to organize data n  easier access/manipulate to data

q  Topics for the next couple of weeks n  Concrete Data Structures

w Arrays and Linked Lists

n  Algorithmic Analysis n  Recursion

13

Arrays 14

Arrays

© 2014 Goodrich, Tamassia, Goldwasser

Java Example: Game Entries q  A game entry stores the name of a player and her best score so far in a game

© 2014 Goodrich, Tamassia, Goldwasser Arrays 15

Java Example: Scoreboard


q  Keep track of players and their best scores in an array, board n  The elements of board are objects of class GameEntry

n  Array board is sorted by score

Arrays 17

Array Definition q  An array is a sequenced collection of

variables all of the same type. Each variable, or cell, in an array has an index, which uniquely refers to the value stored in that cell. The cells of an array, A, are numbered 0, 1, 2, and so on.

q  Each value stored in an array is often called an element of that array.

A 0 1 2 n i


Arrays 18

Array Length and Capacity q  Since the length of an array determines the

maximum number of things that can be stored in the array, we will sometimes refer to the length of an array as its capacity.

q  In Java, the length of an array named a can be accessed using the syntax a.length. Thus, the cells of an array, a, are numbered 0, 1, 2, and so on, up through a.length−1, and the cell with index k can be accessed with syntax a[k].

a 0 1 2 n k


Declaring Arrays (first way) q  The first way to create an array is to use an

assignment to a literal form when initially declaring the array, using a syntax as:

q  The elementType can be any Java base type or class name, and arrayName can be any valid Java identifier. The initial values must be of the same type as the array.


Declaring Arrays (second way) q  The second way to create an array is to use

the new operator. n  However, because an array is not an instance of a

class, we do not use a typical constructor. Instead we use the syntax:

new elementType[length] q  length is a positive integer denoting the length

of the new array. q  The new operator returns a reference to the

new array, and typically this would be assigned to an array variable.


Arrays of Characters or Object References q  An array can store primitive elements, such as

characters.

q  An array can also store references to objects.


Arrays 22

Adding an Entry q  To add an entry e into array board at index i, we

need to make room for it by shifting forward the n - i entries board[i], …, board[n – 1]

board 0 1 2 n i

board 0 1 2 n i

0 1 2 n e i


board

Java Example


Arrays 24

Removing an Entry q  To remove the entry e at index i, we need to fill the hole

left by e by shifting backward the n - i - 1 elements board[i + 1], …, board[n – 1]

0 1 2 n i

0 1 2 n e i

0 1 2 n i


board

board

board

Java Example


Sorting an Array – Insertion Sort

26 Arrays

Code Fragment 3.6

Insertion Sort - Example

Arrays 27

insert

insert

insert

0

0

0

0

0

0

0

0

00

0 0

Done!

0

C E H G F

B C A E H G FD

B E H G FC D

A H G FB C D E

A FB C D E H

A G FB C D E H

E H G FDCBB E

C

F

F

G

H G FDC

A FB C D E H

C D E HG

BA

D

A B C D E G H A B C

A

G

H

E

A

D

D E HG

HGFED

A

C

B

B A

2 3 4 5 6 7

1 2 3 4 5 6 7

1 2 3 4 5 6 7

1 2 3 4 5 6 7

1 2 3 4 5 6 7

1 2 3 4 5 6 7

1 2 3 4 5 6 7

1 2 3 4 5 6 71 2 3 4 5 6 7

1

1

2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7

cur

1 2 3 4 5 6 7

move movemove

no move

no move

no move

no move

move no move

move move no move

Figure 3.5

Drawbacks of Arrays q  Fixed capacity q  Insertions and Deletions involve many

shifting operations

Arrays 28

Singly Linked Lists 29

Singly Linked Lists


Singly Linked List q  A singly linked list is a

concrete data structure consisting of a sequence of nodes, starting from a head pointer

q  Each node stores n  element n  link to the next node

next

element node

A B C D

∅

head



A Nested Node Class



Accessor Methods



Inserting at the Head •  Allocate new

node •  Insert new

element •  Have new

node point to old head

•  Update head to point to new node


Inserting at the Tail •  Allocate a new node

•  Insert new element

•  Have new node point to null

•  Have old last node point to new node

•  Update tail to point to new node

Singly Linked Lists 34 © 2014 Goodrich, Tamassia, Goldwasser


Java Methods


Removing at the Head

•  Update head to point to next node in the list

•  Allow garbage collector to reclaim the former first node



Java Method


Removing at the Tail

•  Removing at the tail of a singly linked list is not efficient!

•  There is no constant-time way to update the tail to point to the previous node


Doubly Linked Lists 39

Doubly Linked Lists


Doubly Linked List q  A doubly linked list can be traversed

forward and backward q  Nodes store:

n  element n  link to the previous node n  link to the next node

q  Special trailer and header nodes

prev next

element

trailer header nodes/positions

elements

node



Insertion q  Insert a new node, q, between p and its successor.

A B X C

A B C

p

A B C

p

X

q

p q



Deletion q  Remove a node, p, from a doubly linked list.

A B C D

p

A B C

D

p

A B C © 2014 Goodrich, Tamassia, Goldwasser

Doubly-Linked List in Java, 2


welcome to csl 201 – data structurescse.iitrpr.ac.in/ckn/courses/f2015/csl201/w1.pdf ·...

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