Download 1 LICE- JTO STUDY MATERIAL DATA STRUCTURE AND

JTO LICE
Data Structure and Algorithms
LICE - JTO
Limited Internal Competitive Examination
STUDY MATERIAL
DATA STRUCTURE AND ALGORITHMS
DATA STRUCTURE AND ALGORITHMS
DATA STRUCTURE AND ALGORITHMS
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JTO LICE
Data Structure and Algorithms
CONTENTS
1. BASIC CONCEPT OF DATA REPRESENTATION
2. INTRODUCTION OF BASIC DATA STRUCTURES AND ALGORITHMS
3. GARBAGE COLLECTION
4. STORAGE ALLOCATION
5. C POINTERS
6. ARRAY
7. STACK
8. QUEUE
9. LINKED LIST
10. TREES AND GRAPHS
11. INTRODUCTION TO ALGORITHM DESIGN
12. RECURRENCE RELATION
13. DIVIDE AND CONQUER
14. OTHER SORTING ALGORITHMS
LICE Practice test at the End of chapter
SYLLABUS:
Basis concepts of data representation, introduction to algorithms design and data structure,
Arrays stacks and queues, linked lists, storage allocation and garbage collection, symbol
tables, Searching, Sorting and Merging Techniques.
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Data Structure and Algorithms
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1. Basic concept of Data Representation
Data Representation refers to the methods used internally to represent information stored in
a computer. Computers store lots of different types of information:

numbers

text

graphics of many varieties (stills, video, animation)

sound
At least, these all seem different to us. However, ALL types of information stored in a
computer are stored internally in the same simple format: a sequence of 0's and 1's. How can
a sequence of 0's and 1's represent things as diverse as your photograph, your favorite song, a
recent movie, and your term paper?
It all depends on how we interpret the information. Computers use numeric codes to
represent all the information they store. These codes are similar to those you may have used
as a child to encrypt secret notes: let 1 stand for A, 2 stand for B, etc. With this code, any
written message can be represented numerically. The codes used by computers are a bit more
sophisticated, and they are based on the binary number system (base two) instead of the
more familiar (for the moment, at least!) decimal system. Computers use a variety of
different codes. Some are used for numbers, others for text, and still others for sound and
graphics.
Memory Structure in Computer

Memory consists of bits (0 or 1)
o

bytes (=8 bits)
o

a single bit can represent two pieces of information
a single byte can represent 256 = 2x2x2x2x2x2x2x2 = 28 pieces of information
words (=2,4, or 8 bytes)
o
a 2 byte word can represent 2562 pieces of information (approximately 65
thousand).

Byte addressable - each byte has its own address.
Binary Numbers
Normally we write numbers using digits 0 to 9. This is called base 10. However, any positive
integer (whole number) can be easily represented by a sequence of 0's and 1's. Numbers in
this form are said to be in base 2 and they are called binary numbers. Base 10 numbers use a
positional system based on powers of 10 to indicate their value. The number 123 is really 1
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JTO LICE
Data Structure and Algorithms
hundred + 2 tens + 3 ones. The value of each position is determined by ever-higher powers
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of 10, read from left to right. Base 2 works the same way, just with different powers. The
number 101 in base 2 is really 1 four + 0 twos + 1 one (which equals 5 in base 10).
Text
Text can be represented easily by assigning a unique numeric value for each symbol used in
the text. For example, the widely used ASCII code (American Standard Code for Information
Interchange) defines 128 different symbols (all the characters found on a standard keyboard,
plus a few extra), and assigns to each a unique numeric code between 0 and 127. In ASCII,
an "A" is 65," B" is 66, "a" is 97, "b" is 98, and so forth. When you save a file as "plain text", it
is stored using ASCII. ASCII format uses 1 byte per character 1 byte gives only 256 (128
standard and 128 non-standard) possible characters The code value for any character can be
converted to base 2, so any written message made up of ASCII characters can be converted to
a string of 0's and 1's.
Graphics
Graphics that are displayed on a computer screen consist of pixels: the tiny "dots" of color
that collectively "paint" a graphic image on a computer screen. The pixels are organized into
many rows on the screen. In one common configuration, each row is 640 pixels long, and
there are 480 such rows. Another configuration (and the one used on the screens in the lab) is
800 pixels per row with 600 rows, which is referred to as a "resolution of 800x600." Each pixel
has two properties: its location on the screen and its color.
A graphic image can be represented by a list of pixels. Imagine all the rows of pixels on the
screen laid out end to end in one long row. This gives the pixel list, and a pixel's location in
the list corresponds to its position on the screen. A pixel's color is represented by a binary
code, and consists of a certain number of bits. In a monochrome (black and white) image, only
1 bit is needed per pixel: 0 for black, 1 for white, for example. A 16 color image requires 4 bits
per pixel. Modern display hardware allows for 24 bits per pixel, which provides an
astounding array of 16.7 million possible colors for each pixel!
Compression
Files today are so information-rich that they have become very large. This is particularly true
of graphics files. With so many pixels in the list, and so many bits per pixel, a graphic file can
easily take up over a megabyte of storage. Files containing large software applications can
require 50 megabytes or more! This causes two problems: it becomes costly to store the files
(requires many floppy disks or excessive room on a hard drive), and it becomes costly to
transmit these files over networks and phone lines because the transmission takes a long
time. In addition to studying how various types of data are represented, you will have the
opportunity today to look at a technique known as data compression. The basic idea of
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Data Structure and Algorithms
compression is to make a file shorter by removing redundancies (repeated patterns of bits)
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from it. This shortened file must of course be de-compressed - have its redundancies put back
in - in order to be used. However, it can be stored or transmitted in its shorter compressed
form, saving both time and money.
Practice TEST -LICE
1. In BCD code, the maximum possible characters set size is
A. character set of 64
B. character set of 84
C. character set of 94
D. character set of 104
Ans-A
2. A small group of bits treated as a single unit is called as
A. bits
B. binary characters
C. input characters
D. bytes
Ans-D
3. The most commonly used codes for representing the bits are
A. ASCII
B. BCD
C. EBCDIC
D. all of above
Ans-D
4. The different characters that can be encoded is 2n where n is
A. number of bits for each character
B. number of bytes for each character
C. number of mega bytes
D. number of gigabytes
Ans-A
5. The numbers that are written with base 16 are classified as
A. whole numbers
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Data Structure and Algorithms
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B. hexadecimal
C. exponential integers
D. mantissa
Ans-B
6. The pictures and graphs that are to be printed with the help of chosen characters are called
A. graphics characters
B. alphanumeric characters
C. character sets
D. control characters
Ans-A
7. The complete set of special characters used by any system is classified as
A. control characters
B. graphics characters
C. character set
D.
alphanumeric characters
Ans-C
8. The one value which is written with the mantissa and the exponent is called
A. exponent
B. mantissa
C. base power
D. floating point number
Ans-D
9. In ASCII code, the maximum possible characters set size is
A. character set of 128
B. character set of 138
C. character set of 148
D. character set of 158
Ans- A
10. The code 'EBCDIC' that is used in computing stands for
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Data Structure and Algorithms
A. extended BCD interchange code
JTO LICE
B. extension of BCD information code
C. extension of BCD interchange conduct
D. extended BCD information conduct
Ans- A
11. All the decimal values and all the integers are included in set of
A. whole numbers
B. natural numbers
C. real numbers
D. integers
Ans- C
12. The number of bits in 'ASCII' code used in computing are
A. five bits
B. six bits
C. twenty bits
D. ten bits
Ans- C
13. The symbols such as letters or any digit are called
A. characters
B. small bits
C. small bytes
D. output characters
Ans- A
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Data Structure and Algorithms
JTO LICE
2.
8
Introduction of Basic Data Structures and Algorithms
A data structure is an arrangement of data in a computer's memory or even disk storage. An
example of several common data structures are arrays, linked lists, queues, stacks, binary
trees, and hash tables. Algorithms, on the other hand, are used to manipulate the data
contained in these data structures as in searching and sorting.
Many algorithms apply directly to a specific data structures. When working with certain data
structures you need to know how to insert new data, search for a specified item, and deleting
a specific item.
Commonly used algorithms include are useful for:



Searching for a particular data item (or record).
Sorting the data. There are many ways to sort data. Simple sorting, Advanced sorting
Iterating through all the items in a data structure. (Visiting each item in turn so as to
display it or perform some other action on these items)
Characteristics of Data Structures
Data Structure
Array
Ordered Array
Advantages
Quick inserts
Fast access if index
known<
Faster search than
unsorted array
Last-in, first-out access
First-in, first-out access
Quick inserts
Quick deletes
Binary Tree
Quick search
Quick inserts
Quick deletes
(If the tree remains
balanced)
Red-Black Tree Quick search
Quick inserts
Quick deletes
(Tree always remains
balanced)
2-3-4 Tree
Quick search
Quick inserts
Quick deletes
(Tree always remains
balanced)
(Similar trees good for disk
storage)
Hash Table
Very fast access if key is
known
Stack
Queue
Linked List
Disadvantages
Slow search
Slow deletes
Fixed size
Slow inserts
Slow deletes
Fixed size
Slow access to other items
Slow access to other items
Slow search
Deletion algorithm is complex
Complex to implement
Complex to implement
Slow deletes
Access slow if key is not known
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Heap
Graph
Data Structure and Algorithms
Quick inserts
Quick inserts
Quick deletes
Access to largest item
Best models real-world
situations
Inefficient memory usage
Slow access to other items
Some algorithms are slow and
very complex
Practice Question-MCQ LICE
1. Which of the following data structure is non-linear type?
A) Strings
B) Lists
C) Stacks
D) Tree
Ans-D
2. Which of the following data structure is linear type?
A) Array
B) Tree
C) Graphs
D) Hierarchy
Ans-A
3. The logical or mathematical model of a particular organization of data is
called a .........
A) Data structure
B) Data arrangement
C) Data configuration
D) Data formation
Ans-A
4. The simplest type of data structure is ..................
A) Multidimensional array
B) Linear array
C) Two dimensional array
D) Three dimensional array
AnsB
5. Linear arrays are also called ...................
A) Straight line array
B) One-dimensional array
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C) Vertical array
D) Horizontal array
Ans-B
Data Structure and Algorithms
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6. Arrays are best data structures ............
A) For relatively permanent collections of data.
B) For the size of the structure and the data in the structure are constantly
changing
C) For both of above situation
D) For none of the above
Ans-A
7. Which of the following data structures are indexed structures?
A) Linear arrays
B) Linked lists
C) Graphs
D) Trees
Ans-A
8. Each node in a linked list has two pairs of .............. and ...................
A) Link field and information field
B) Link field and avail field
C) Avail field and information field
D) Address field and link field
Ans-A
9. A ........................ does not keep track of address of every element in the
list.
A) Stack
B) String
C) Linear array
D) Queue
Ans-C
10. When does top value of the stack changes?
A) Before deletion
B) While checking underflow
C) At the time of deletion
D) After deletion
Ans-D
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JTO LICE
Data Structure and Algorithms
3.
Garbage collection
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Garbage collection (GC) is a dynamic approach to automatic memory management and heap
allocation that processes and identifies dead memory blocks and reallocates storage for reuse.
The primary purpose of garbage collection is to reduce memory leaks.
Garbage collection implementation requires three primary approaches:

Mark-and-sweep - In process when memory runs out, the GC locates all accessible
memory and then reclaims available memory.

Reference counting - Allocated objects contain a reference count of the referencing
number. When the memory count is zero, the object is garbage and is then destroyed.
The freed memory returns to the memory heap.

Copy collection - There are two memory partitions. If the first partition is full, the GC
locates all accessible data structures and copies them to the second partition,
compacting memory after GC process and allowing continuous free memory.
Storage allocation
There are two type of storage allocation:
1. Static memory allocation
2. Dynamic memory allocation
STATIC MEMORY ALLOCATION
Static memory allocation is the allocation of memory at compile-time before the associated
program is executed, unlike dynamic memory allocation or automatic memory
allocation where memory is allocated as required at run-time.
An application of this technique involves a program module (e.g. function or subroutine)
declaring static data locally, such that these data are inaccessible in other modules unless
references to it are passed as parameters or returned. A single copy of static data is retained
and accessible through many calls to the function in which it is declared. Static memory
allocation therefore has the advantage of modularizing data within a program design in the
situation where these data must be retained through the runtime of the program
DYANAMIC MEMORY ALLOCATION
A computer system in which memory capacity is made available to a program on the basis of
actual, momentary needduring program execution, and areas of storage may be reassigned at
any time. Also known as dynamic allocation; dynamic memory allocation.
Two basic operations in dynamic storage management:
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Data Structure and Algorithms
o Allocate a given number of bytes
o Free a previously allocated block
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Two general approaches to dynamic storage allocation:
o Stack allocation (hierarchical): restricted, but simple and efficient.
o Heap allocation: more general, but less efficient, more difficult to implement.
Stack Allocation
 A stack can be used when memory allocation and freeing are partially predictable: memory
is freed in opposite order from allocation. If alloc(A) then alloc(B) then alloc(C), then it will
be free(C) then free(B) then free(A).
 Example: procedure call. X calls Y calls Y again.
 Stacks are also useful for lots of other things: tree traversal, expression evaluation, top-
down recursive descent parsers, etc.
 A stack-based organization keeps all the free space together in one place.
Heap Allocation
 Heap allocation must be used when allocation and release are unpredictable
 Memory consists of allocated areas and free areas (or holes). Inevitably end up with lots of
holes.
 Goal: reuse the space in holes to keep the number of holes small, keep their size large.
 Fragmentation: inefficient use of memory due to holes that are too small to be useful.
Stack allocation is perfect: only one hole.
 Typically, heap allocation schemes use a free list to keep track of the storage that is not in
use.
 Best fit: keep linked list of free blocks, search the whole list on each allocation, choose
block that comes closest to matching the needs of the allocation, save the excess for later.
During release operations, merge adjacent free blocks.
 First fit: just scan list for the first hole that is large enough. Free excess. Also merge on
releases. Most first fit implementations are rotating first fit.
 Best fit is not necessarily better than first fit!
 First fit tends to leave "average" size holes, while best fit tends to leave some very large
ones, some very small ones. The very small ones can't be used very easily.
Symbol table
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Data Structure and Algorithms
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a symbol table is a data structure used by a language translator such as
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a compiler or interpreter, where each identifier in a program's source code is associated with
information relating to its declaration or appearance in the source.
A C compiler that parses this code will contain at least the following symbol table entries:
Symbol name
bar
Type
Scope
function, double
Extern
double
function parameter
function, double
Global
count
int
function parameter
sum
double
block local
int
for-loop statement
x
foo
i
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