Data Structures

1
Data Structures

• Lecture 2 Array
• Azhar Maqsood
• NUST Institute of Information Technology (NIIT)

2
Features of c you need to know

• Variables
• Parameter Passing
• Pointers
• Classes and Objects
• Inheritance
• Others

3
Variables

• You must be very comfortable with the notion of a
  variable as an abstraction for a region of a
  memory. A variable has attributes such as name,
  type, value, address size, lifetime and scope.

4
Parameter Passing

• There are two parameter passing mechanisms in
  C pass-by-value and pass-by-reference. It is
  essential that you understand the behavioral
  difference between the two methods as well as the
  performance implications of using each of them.

5
Pointers

• Mastering the use of pointers is essential when
  programming in C. The key to understanding
  pointers is to
• recognize that a pointer variable has exactly
  the same set of attributes as any other C
  variable.
• It is crucial that you keep straight the
  distinctions between the
• value of a pointer,
• the address of a pointer
• the object to which a pointer points.

6
Classes and Objects

• A C class encapsulates a set of
• Values
• The values are represented by the member
  variables of the class
• operations.
• The operations by the member functions of the
  class.
• In C a class definition introduces a new type.
• The instances of a class type are called objects.
  
• Special role of the constructor and the
  destructor member functions of a class and when
  the C compiler invokes each of them.

7
Inheritance

• In C one class may be derived from another. The
  derived class inherits
• all the member variables and the member functions
  of the base class or classes.
• In addition, inherited member functions can be
  overridden in the derived class and new member
  variables and functions can be defined.
• You should understand how the compiler determines
  the code to execute when a particular member
  function is called.

8
Inheritance

• In C one class may be derived from another.
• The derived class inherits all the member
  variables and the member functions of the base
  class or classes.
• In addition, inherited member functions can be
  overridden in the derived class and new member
  variables and functions can be defined.
• You should understand how the compiler determines
  the code to execute when a particular member
  function is called.

9
Other Features

• features such as
• templates,
• exceptions
• run-time type information
• and more as we learn further

10
Features of c you need to know

• Variables
• Parameter Passing
• Pointers
• Classes and Objects
• Inheritance
• Others

11
In Todays lecture

• How to Input arrays
• How to process arrays
• How to insert an item in an array
• How to pass an array
• Structures
• Their basic implementation

12
The first Data Structure

• An Array!
• The simplest form of an Array is a one
  dimensional array that may be defined as a finite
  ordered set of homogenous elements
• For Example
• int a100

13
Basic Operations

• Extraction
• A function that accepts an array a and an index
  i, and returns an element of the array.
• Example
• ai
• Storing
• It accepts array a an index i and an element
  x.
• Example
• aix

14
One Dimensional Array

• range upper - lower1
• Neither the upper bound nor the lower bound can
  be changed and as well as the range can be
  changed during the program execution.

Lower Bound 0
Range
Upper Bound
15
Implementation of 1Dimenional Array

• int b100
• Reserves 100 successive locations, each large
  enough to contain a single integer.
• The address of the first of these locations is
  called the base Address base(b)
• Reference to element b0 is to the element at
  location base(b)
• Reference to b1 is to the element at
• base(b) 1 esize
• Hence
• b gives you the starting memory address of the
  array b

16
Memory view of an array
2 3 4 7 8
int a5
//Help me give output of this program void
main(void) int a5 2,3,4,7,8 cout
ltlt a3 ltlt endl cout ltlt a ltltendl cout ltlt
(a1) ltltendl cout ltlt a1 ltltendl

2
3
4
7
8



a0
a1
a2
a3
a4



0x4
0x8
0xC
0x10
0x14


17

• a 1 without brackets leads to adding 1 to
  contents (value) of a0

18
Array of Variable Length

A0
A1
A2
A3



5 H E L L O
6 B I C S E 4
19
Array of Variable length cont.
char A4

A0
A1
A2
A3



H E L L O \0
B I C S E 2 \0
C O T T O N \0
p e n \0
20
Character arrays (Strings)Review

A
L
I
\0
Garbage



A0
A1
A2
A3
A4


A L I \0
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How to determine length of the string

• include ltiostream.hgt
• include ltconio.hgt
• include ltstdio.hgt
• int len_str(char str25)
• int len_str_while(char s25)
• void main(void)
• char l25
• cin gtgt l
• cout ltlt len_str(l) ltlt endl ltlt len_str_while(l)
• //function with for loop
• int len_str(char s25)
• for (int i 0 si ! '\0' i)
• return i

22
Cont

• //another method using while loop
• int len_str_while(char s25)
• int i0
• while (si ! '\0')
• i
• return i

23
Two dimensional Arrays
Do it yourself
24
Main Program

• include ltiostream.hgt
• include ltconio.hgt
• void mult_matrices(int a2, int b2, int
  result2)
• void print_matrix(int a2)
• void main(void)
• int p22 10, 20, 30,40
• int q22 50, 60, 70, 80
• int r22
• print_matrix(p)
• print_matrix(q)
• mult_matrices(p, q, r)
• print_matrix(r)

Why New Array?
25
Print a Matrix

• void print_matrix(int a2)
• int i, j
• for (i0 ilt2 i)
• for (j0 jlt2 j)
• cout ltlt "\t" ltlt aij
• cout ltlt endl
• cout ltlt endl

Why mention 2?
26
Multiply a Matrix

• void mult_matrices(int a2, int b2, int
  result2)
• int i, j, k
• for(i0 ilt2 i)
• for(j0 jlt2 j)
• resultij 0
• for(k0 klt2 k)
• resultij resultij (aik
  bkj)

Why passed so many variables? Are
these Variables Called by reference or By value?
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Submission Date

• 13th March, 2008
• Before 1500 Hrs
• Late submission rules apply