00. Basics of DS

8/8/2019 00. Basics of DS

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(C) GOYANI MAHESH(C) GOYANI MAHESH 11

DATASTRUCTURES

MAHESH GOYANI

M AHATMAG ANDHI INSTITUE OF TECHNICALEDUCATION & RESEARCH CENTER

[email protected]




PROGRAMMING

METHODOLOGY




Data Structure is structural representation of logical relationship betweenelements of Data.

DS is used for utilizing the maximum efficiency of Memory

Organized Data + Operation = Data Structure

Algorithm + Data Structure = Program.

ALGORITHM : Its a step by step finite sequence of instruction to solve a welldefined computational problem.

Optimization of program is directly concerned with the algorithm design.

Representation of DS in memory of a computer is called storage structure.

A Storage structure stored in auxiliary memory is known as File Structure.

TERMINOLOGY




Informal Algorithm

MathematicalModel

PsedoLanguage

Program

FormalLanguage

C / C++

Program

Data

Structure

STEP WISE REFINEMENT




Modular Programming is an act of writing programs as functions, that eachone perform a single well defined task, and which have minimum interactionbetween them.

High cohesion : Related with specific task only.

Low Coupling : Independent from each other.

Two Methods:

(i). TOP DOWN Methodology (eg. C, C++ Programming)

(ii). BOTTOM UP Methodology (eg. VB Project implementation)

MODULAR PROGRAMMING




Main

Function 1 Function 2 Function 3

Function a Function b Function c Function c Function b Function d

Functions called By Function 1 Functions called By Function 3Functions called

By Function 1

PROGRAMMING APPROCH




Sequence of sequentially executed statements

Conditional Execution (if)

Looping or iteration (for, while, do-while)

Structured Subroutine (Function)

STRUCTURED PROGRAMMING




ARRAYS

An array is a collection of homogeneousdata elements described by a single name.

Insertion and Deletion can not be made.

i. 1-D Array

ii. 2-D Array

iii. M-D Array

iv. Sparse Arrays

VECTOR 1-D ordered collection of number

i. Row Vector

ii. Column Vector

LISTS A list is an ordered set consisting of a varying A list is an ordered set consisting of a varyingnumber of elements to which insertion andnumber of elements to which insertion anddeletion can be madedeletion can be made

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SOME D.S.




FILES & RECORDS

File is typically large list that is stored in theexternal memory of computer.

A record is collection of information about someparticular entity.

Record may be collection of heterogeneous data.

File is collection of such a records.

CHARECTERISTICS

OF STRING

Fixed length string

Variable length string

Linear list (Linked List)




Data

Structure

PrimitiveData Structure

Non-PrimitiveData Structure

int char float pointer

Linear

list

Graph Tree

list Array File

Non - Linear

list

Stack Queue

CLASSIFICATION OF D.S.




malloc ()

Allocates 1 block of memory

ptr=(Data_Type *)malloc(n * sizeof(Data_Type));

callloc ()

Allocates n block of memory

ptr=(Data_Type *)calloc(n , sizeof(Data_Type));

realloc ()

Resize the original block of memory

ptr=realloc(ptr, NewSize);

free ()

Free up the memory block

free (ptr);

Dynamic or Run Time memoryallocation (Linked list)

Static or Compile Timememory allocation (Array)

int a, array[10];

char str[80];

Dynamic memoryallocation in C++

int *var1 = new int;

float *var2 = new float;

delete var1;

delete var2;

MEMORY MANAGEMENT




Free Storage List

Garbage Collection

Dangling Reference

Reference Counter

MEMORY MANAGEMENT




BUDDY SYSTEM

K eep separate free list for block of different sizes.

e.g. if memory contain 1024 word than it might be divided in 1 block of 256 words, 2 blocks of 128 words,4 blocks of 64 words and 8 blocks of 32 words

This scheme has several drawback, Like fragmentation waste space.

Buddy system contains several free lists consisting of various sized block.

Very efficient in binary computer, where shift operation is performed well.

initially entire memory is considered as free block of size 2m

Block of size i is called i-Block & free list containing i-Block is called i-List.

Block must be allocated only in size of 2k, 0<k<m.

if request for block size n is made, an i-block is reserved where I is the smallest integer such that n<=2i

if i-list is not free then bring block from (i+1)-list and divide in to two i-block, one will be used and anotherwill be added into i-list. Do Recursively.

if an (i+1) block is divided in two i-block b1 & b2, b1 and b2 are buddies of each other. Block at locationp is called i-Buddy of p. buddies can be more than one but i-buddy can not.

if an i-block is freed and its i-buddy is already freed than two buddies are combined into (i+1) block.




768

Free Size 29

Free Size 28

Free Size 28

B1 Allocated Size 27

0

512

896

9:0

8:512

7:768

Free Size 29

Free Size 28

Free Size 26


0

512

768

896

9:0

8:512

6:768

B2 Allocated Size 2

6832




Free Size 29

Free Size 28



0

512

768

896

9:0

8:512

7:768

6:768

B2 Allocated Size 2

6832

Free Size 29

Free Size 27


0

512

768

896

9:0

8:512

B2 Allocated Size 2

6 832




640

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00. Basics of DS