Chapter 4

Chapter 4
Arrays
Ragia A. Ibrahim, Ph.D. Student
1
‫القاهرة‬ ‫جامعة‬
‫االحصائيه‬ ‫والبحوث‬ ‫الدراسات‬ ‫معهد‬
‫مركز‬‫والبرمجيات‬ ‫المعلومات‬ ‫قواعد‬ ‫بحوث‬

‫االحصائيه‬ ‫والبحوث‬ ‫الدراسات‬ ‫معهد‬ ‫القاهرة‬ ‫جامعة‬
‫والبرمجيات‬ ‫المعلومات‬ ‫قواعد‬ ‫بحوث‬ ‫مركز‬
2
Arrays used to group of similar type data items. Accessed
via an index.
Array Declaration examples
int myarray[100];
Data
Type
Name
Size
Introduction
Brackets delimits array size
char name[30];
float salaries[10];

Array Elements-1
3

Array Elements-2
4
44
16
23
68
Age[0]
Age[1]
Age[2]
Age[3]

5
Insert 4 students ages into an array
#include<iostream.h>
Int main()
{
float age[4];
for(int i=0;i<4;i++)
{
cout<<“Enter an age”;
cin>>age[i];
}
/ / to print the array values
for(int i=0;i<4;i++)
cout<<“you Entered”<<age[i];
// why no {} in the second for?
Return 0;
}
Example - 1
Enter an age:44
Enter an age:16
Enter an age:23
Enter an age:68
You entered 44
You entered 16
You entered 23
You entered 68
Array element accessed twice.
The first time: insert a value into
array
cin>>age[j];
The second time: we read it
cout<< “you entered”<<age[i];

6
6
Sales: enter 6 sales values , calc avrg , sum.
Int main()
{
const int size=6; //size of array
double sales[size]; //array of 6 variable
cout<<“enter widget sales for 6 days n”;
for (int j=0; j<size; j++) //puts figures from array
{
cin<<sales[j];
total+=sales[j]; // to find total
}
// -------
double average = total/size; //to find average
cout<<“average= ”<<average<<endl;
return 0;
}
Example - 2
variables declared with ‘const’
added become constants
Enter widget sales for 6
days
352.64
867.70
781.32
867.35
746.21
189.45
Average = 634.11

Syntax of array initialization
By: Ragia Ibrahim 7
Assignment operator Intialize values
int coins [6]or[] = [1,5,10,25,50,100];
braces
Array size (optional)
commas

Initializing Array
days from start of year to date specified
Int main()
{
//shows days from start of year to date specified
int month, day, total_days;
int days_per_month[12] = {31,28,31,30,31,30,31,31,30,31,30,31};
cout<<“n enter month(1 to 12):”; //get date
cin>>month;
cout<<“n enter day (1 to 31):”;
cin>>day;
total_days=days; //seprate days
for (int j=0;j<month-1;j++) //add days each month
total_days +=days_per_month[j];
cout<<“total days from start of year is:”<<total_days<<endl;
return 0;
}
days_per_month[0]
days_per_month[1]
days_per_month[2]
days_per_month[3]
days_per_month[4]
days_per_month[5]
days_per_month[6]
days_per_month[7]
days_per_month[8]
days_per_month[9]
days_per_month[10]
days_per_month[11]

Multidimensional array
• //salemon.cpp
• //display sales chart using 2.d array
• #include <iostream.h>
• #include <iomanip.h>
• Const int districts=4;
• Const int months=3;
How to represent Sales for each district per month ?

10
Defining multidimensional arrays
District 1
District 2
District 3
District 4
Month
1 2 3
Sales[0][0]
Sales[0][1]
Sales[0][2]
Sales[1][0]
Sales[1][1]
Sales[1][2]
Sales[2][0]
Sales[2][1]
Sales[2][2]
Sales[3][0]
Sales[3][1]
Sales[3][2]
double sales[districts][month];

#include <iostream>
const int district= 4;
const int month= 3;
Int main()
{
int d,m;
d=0; m=0;
double sales[d] [m] ;
for(int d=0; d<districts; d++)
for(int m=0; m<months; m++)
{
cout<<"Enter sales for district (" << d+1 <<')' ;
cout<<" and Enter month (" << m+1 <<") : " ;
cin>>sales[d][m];
} //put number in array }

12
// program continue
cout<<“nn”;
cout<<“ monthn”;
// can we display array values ?? when
for(int d=0; d<4; d++)
for(int m=0; m<3; m++)
{
for(int m=0;m<months;m++) //display array values
cout<<“n District ”<< d+1 << “Month:” <<m+1;
cout << sales[d][m];
} //end for
Cout <<endl;
return 0;
} //end main
cout<<setiosflags(ios::fixed) //not exponential
<<setiosflags(ios::showpoint) //always use point
<<setprecision(2) //digits to right
<<setw(10) //field width
cout <<sales[d][m]; //get number from array

13
sales[districts][months]= {
{1432.07,234.5,654.01},
{322.00,13838.32,17589.88},
{9328.34,934.00,449.30} ,
{12838.29,2332.63,32.93}};
//two-dimensional array definition with
initialization
Initialization for Multidimensional Array

14
String ??
A
M
A
N
U
E
N
S
I
S
0
Terminating 0 or null byte
representing by ‘0’
characters constant
Characters in string
string
String
buffer
str
Unused part of buffer
String stored in array of char’s variable
Str={‘A’, ‘M’, ‘A’, ’N’, ’U’, ’E,’…}

15
Int main()
{
char str[80];
cout<<“Enter String :”;
cin>>str;
return 0;
}
String - variable

16
//constant string
Int main()
{
char str[]=“farewell! Thou art too dear for my possessing.”;
cout<<str<<endl;
return 0;
}
String Constant

17
Int main()
{
char str1[]=“Welcome to ISSR.”;
char str2[80];
Int j=0;
while(str1[j]!=’0’;
{
str2[j]=str1[j];
j++;
}
Str2[j]=“0” //adding termination.
cout<< str2;
return 0;
}
String -Copying

18
Int main()
{
char weekDays[7][10] = {
“Monday “, “ Tuesday “, “ Wednesday“,
“Thursday“, “Friday“, “Saturday“, “Sunday“};
For ( int j =0; j< 7 ; j++)
cout<< weekDays[j]<<endl;
return 0;
}
Array of String

19

20
Q3: Write C++ prog. to reverse string.
#include<iostream>
using namespace std;
int main()
{
char str[10];
int i, len;
cout << "Enter a string: ";
cin>>str;
i=0; //intial value
while (str[i]!='0')
i++;
len=i;
// print in reversed order starting from string end to first..
for(i = len-1; i>=0; i--)
cout<<str[i];
cin.get();
return 0;
}

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