data structures lab 1 ta: nouf al-harbi [email protected]
TRANSCRIPT
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Introductiom to C++
What’s Data Structures ..?
a data structure is a particular way of storing and organizing data in a computer so that it can be used efficiently
Different kinds of data structures are suited to different kinds of applications
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Understand the purposes and methods of the most commonly occurring data structures Analyze the data structure needs of particular problems Write C++ applications using data structures discussed in the course
Data Structures LAB Objectives
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LAB Marks
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Lab Materials..
DATA STRUCTURES LAB 1
Introduction to C++
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objectives
Quick Review of some topics in C++ : Arrays Structures Classes
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Data types in C++Data types
simple
int
char
double
composite
array
struct
class
Note : Not all the data types are included just some examples
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Arrays
Suppose we want to compute the average of 20 marks. Do we need to declare 20 variables
mark1, mark2, …, mark20? Do we need to write 20 couts and 20 cins? How about sorting a large number of ints?
This is where ARRAYS come in!
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Introduction to Arrays
An array is a fundamental data structure used to store objects of a particular type
in contiguous memory locations Arrays allow us to randomly access this
contiguous memory via indexing
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Array :Declaration
typeName arrayName[sizeOfTheArray]
typeName the type of the elements of the array Can be any type (primitive or user-
defined) arrayName the name of the array.
Any valid C++ identifier sizeOfTheArray the size or the capacity
of the array
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Array : Declaration
An array consisting of 5 variables of type int is declared:
It creates 5 int type variables which are accessed as score[0], score[1] , score[2], score[3], score[4]
These are called indexed variables or subscripted variables
The number in the brackets index or subscript Array subscripts (0 size of the array-1), which is
4.
int score[5];
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Array : Initialization
You may initialize specific index variables
this can also be read from cin You can use for statement to initialized
the values of an array
score[4] = 10;
for (int i=0;i<5;i++)
score[i]=i*i+1;
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Arrays : Initialization
The size of an array can be omitted
The following definition is also possible
Initialization may cover only the first few elements
the first two elements are initialized to 1 and 2
The others to the default value
int score[]={2, 1, 5, 4, 6};
int score[5]={2, 1, 5, 4, 6};
int marks[10]={1,2};
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Referencing and using arrays
Array references may be used anywhere an ordinary variable is used
The for statement is a good way to go through the elements of an array
cin >> score[4] >> score[2];cout << score[2] << “, “ << score[4];
score[0] = 32;score[3] = score[0]++;
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Array Example
Write a program that defines an array
called StdMarksAvg have 5 elements
Allow the user to enter the 5 Marks
Calculate the Average of marks ..
Then print it out
#include<iostream.h>int main(){int StdMarksAvg[5],i=0;double sum=0,avg=0;cout<<"Enter the Students Marks"<<endl;for (i=0;i<5;i++){cout<<"the mark of sudent "<<i+1<<": ";
cin>>StdMarksAvg[i];
sum+=StdMarksAvg[i];}avg=sum/5;cout<<"The Average of Marks="<<avg<<endl;
return 0;}
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Multidimensional Arrays
Multidimensional arrays can be described as “arrays of arrays”
For examplea bidimensional array can be imagined
as a bidimensional table made of elements
all of elements of a same uniform data type
Rows
Columns
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Matrix Example
int maxRows = 2;int maxCols = 3 ;int matrix [ 2] [ 3 ];int row , col ;for ( row = 0 ; row < maxRows ; row ++ ){
for ( col = 0 ; col < maxCols ; col ++ ){
cout << “Please enter value of ”<< row << “, “ << col;
cin >> matrix [ row ] [ col ] ;}
}
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Matrix Example
5 2 9
7 0 4
5 2 9After first outer loop
After second outer loop
Input
Input
[0]
[1]
[0]
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Structure
A Structure is a container, it can hold many things. These things can be of any type.
Structures are used to organize related data (variables) in to a nice package.
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Example - Student Record
Student Record: Name a string HW Grades an array of 3 doubles Test Grades an array of 2 doubles Final Average a double
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Structure Members
Each thing in a structure is called member.
Each member has a name, a type and a value.
Names follow the rules for variable names.
Types can be any defined type.
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Example Structure Definition
struct StudentRecord {
string name; // student namedouble hw[3]; // homework gradesdouble test[2]; // test gradesdouble ave; // final average
};
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Using a struct
By defining a structure you create a new data type.
Once a struct is defined, you can create variables of the new type.
StudentRecord stu;
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Accessing Members
You can treat the members of a struct just like variables.
You need to use the member access operator '.' :
cout << stu.name << endl;stu.hw[2] = 82.3;
stu.ave = total/100;
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Structure Assignment
You can use structures just like variables:
Copies the entire structure
StudentRecord s1,s2;s1.name = “Lama";
…s2 = s1;
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Classes : Introduction
Structures provide a way to group data elements
Functions organize program actions into named entities
we’ll put these ideas together to create Classes
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Classes : What Are Classes?
The functions in the class manipulate the member variables.
A class enables you to encapsulate these variables and functions into one collection (object).
variable
s
• mem
ber
variable
s or
• data
mem
bers
function
s
• member functions
or• methods of
the class
class
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Declaring a Class
class ClassName{
memberList};
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Classes: Data and Method declaration
Data member declarations are normal variable declarations int x; is a data member declaration you cannot initialize data members where
you declare them They must be initialized either in a method or
outside the class. For example, int x = 50; as a data member
declaration causes an error.
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Classes: Data and Method declaration
Method declarations are function declarations placed inside a class a function declaration can also include the
implementation (definition), or you can implement it separately
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Classes: Data and Method declaration
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class Part{int modelnumber;double cost;void SetPart(int mn, double c);void ShowPart();};
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Modelnumber : int
Cost : double SetPart(int
mn ,double c)
void ShowPart()
part
Data
m
em
bers
meth
od
s
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Classes : defining object
An object is an individual instance of a class
You define an object of your new type just as you define an integer variable:
This code defines wheel, which is an object whose class (or type) is Part.
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Part wheel;
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Classes : Calling Data Member and Member Functions
Once you define an actual Part object -for example, wheel You use the dot operator (.) to access the
members of that object. to assign 50 to wheel’s modelnumber
member variable
to call the ShowPart() function
wheel.modelnumber = 50;
wheel.ShowPart();
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Classes: Assign Values to Objects, Not to Classes
In C++ you don't assign values to types you assign values to variables
This is a shorthand way of saying, "Assign 50 to the variable x, which is of type int".
int x; //define x to be an int
x = 50; //set x's value to 50
int = 50; WRONG
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Classes: Assign Values to Objects, Not to Classes
In the same way, you wouldn't write
you must define a Part object and assign 50 to the modelnumber of that object.
Part.modelnumber = 50; //wrong ???
Part wheel; //just like int x;wheel.modelnumber = 50; //just
like x = 50;
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Classes: Using Access Specifiers
C++ allows you to control where the data members of your class can be accessed.
A class has 2 kinds of access specifiers: public and private. Public data members and methods can be
accessed outside the class directly. The public stuff is the interface. Private members and methods are for internal
use only. If no access specifier is provided in the class,
all members default to private.
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Classes: Using Access Specifiers example
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class ClassName{int x;public:int y;int z;private:int a;};
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Classes: Using Access Specifiers
•Modelnumber : int, private•Cost : double, private•SetPart(int mn, •double c), public•void ShowPart(), public
part
Data
m
em
bers
meth
od
s
•Modelnumber =6245•Cost=220
part1
•Modelnumber =6246•Cost=185
Part 2
•Modelnumber =6247•Cost=150
Part 3ob
jec
ts
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private & public Example
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private & public Example
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Special Member Functions
Constructors: called when a new object is created (instantiated) can be many constructors, each can take different
arguments It is normally used to set initial values for the data
members It has the same name as the class cannot have a return value (not even void)
Destructor: called when an object is eliminated only one, has no arguments It is always named the same name as the class, but with a
tilde (~) at the beginning
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Constructor Example 1123456789
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Constructor Example 1123456789
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Constructor Example 3123456789
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Separating Classes into Files
Classes often get pretty big having all your code in one file can quickly become
unmanageable. if you want to reuse your classes in other programs, you
have to copy and paste them into the new program. there is a convention for separating classes into files.
the class declaration is placed in one file (header file) ClassName.h
the implementation of all the methods is put in another fileClassName.cpp
include the header file in your program with an #include directive
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example
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example
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