Chapter 7 Arrays

Chapter 7

Arrays

C++ Programming, Namiq Sultan 1

Namiq Sultan

University of Duhok

Department of Electrical and Computer Engineering

Reference: Starting Out with C++, Tony Gaddis, 2nd Ed.

7.1 Arrays Hold Multiple values

• Unlike regular variables, arrays can hold multiple values.

Figure 7-1

int count Enough memory for 1 int

float price Enough memory for 1 float

56.981

char letter Enough memory for 1 char

Figure 7-2

int Days[6];

Table 7-1

Array Declaration Number of Elements

Size of Each Element

Size of the Array

char le tte rs [25]; 25 1 byte 25 bytes

short r ings[100 ]; 100 2 bytes 200 bytes

int m iles [84 ]; 84 4 bytes 336 bytes

float tem p[12 ]; 12 4 bytes 48 bytes

double dD istance[1000 ]; 1000 8 bytes 8000 bytes

7.2 Accessing Array elements

• The individual elements of an array are assigned unique subscripts. These subscripts are used to access the elements.

Program 7-1

// This program asks the user for the number of hours worked// by 6 employees. It uses a 6-element int array to store the values.

#include <iostream>

int main(void){

short hours[6];

cout << "Enter the hours worked by six employees: ";cin >> hours[0];cin >> hours[1];cin >> hours[2];cin >> hours[3];

cin >> hours[4];cin >> hours[5];cout << "The hours you entered are:";cout << " " << hours[0];cout << " " << hours[1];cout << " " << hours[2];cout << " " << hours[3];cout << " " << hours[4];cout << " " << hours[5] << endl;

Program Output with Example Input

Enter the hours worked by six employees: 20 12 40 30 30 15 [Enter]

The hours you entered are: 20 12 40 30 30 15

Figure 7-7

Program 7-2

// This program asks the user for the number of hours worked// by 6 employees. It uses a 6-element short array to store the values. #include <iostream>

int main(void){

short hours[6];

cout << "Enter the hours worked by six employees: ";for (int count = 0; count < 6; count++)

cin >> hours[count];cout << "The hours you entered are:";for (count = 0; count < 6; count++)

cout << " " << hours[count];cout << endl;

}C++ Programming, Namiq Sultan 11

Enter the hours worked by six employees: 20 12 40 30 30 15 [Enter]

The hours you entered are: 20 12 40 30 30 15

7.4 Array Initialization

• Arrays may be initialized when they are declared.

Program 7-6

// This program displays the number of days in each month.// It uses a 12-element int array.#include <iostream>

int main(){

int days[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};for (int count = 0; count < 12; count++){

cout << "Month " << (count + 1) << " has ";cout << days[count] << " days.\n";

Program Output

Month 1 has 31 days.Month 2 has 28 days.Month 3 has 31 days.Month 4 has 30 days.Month 5 has 31 days.Month 6 has 30 days.Month 7 has 31 days.Month 8 has 31 days.Month 9 has 30 days.Month 10 has 31 days.Month 11 has 30 days.Month 12 has 31 days.

Program 7-7

// This program uses an array of ten characters to store // the first ten letters of the alphabet. The ASCII codes // of the characters are displayed.#include <iostream>

int main(){

char letters[10] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J'};

cout << "Character" << "\t" << "ASCII Code\n";cout << "--------" << "\t" << "----------\n";for (int count = 0; count < 10; count++){

cout << letters[count] << "\t\t";cout << int(letters[count]) << endl;

}} C++ Programming, Namiq Sultan 16

Program Output

Character ASCII Code--------- ----------

A 65B 66C 67D 68E 69F 70G 71H 72I 73

Partial Array Initialization

• When an array is being initialized, C++ does not require a value for every element.

int numbers[7] = {1, 2, 4, 8};

Implicit Array Sizing

• It is possible to declare an array without specifying its size, as long as you provide an initialization list.

float ratings[]={1.0, 1.5, 2.0, 2.5, 3.0};

Initializing With Strings

• When initializing a character array with a string, simply enclose the string in quotation marks:

char name[] = “Warren”;

Figure 7-11

Program 7-9

// This program displays the contents of two char arrays.#include <iostream>

int main(){

char name1[] = "Holly";char name2[] = {'W', 'a', 'r', 'r', 'e', 'n', '\0'};

cout << name1 << endl;cout << name2 << endl;

Program Output

Warren

7.5 Processing Array Contents

• Individual array elements are processed like any other type of variable.

Program 7-10

// This program stores, in an array, the hours worked by 5// employees who all make the same hourly wage.#include <iostream>int main(){

int hours[5];float payRate;

cout << "Enter the hours worked by 5 employees who all\n";cout << "earn the same hourly rate.\n";for (int index = 0; index < 5; index++){

cout << "Employee #" << (index + 1) << ": ";cin >> hours[index];

cout << "Enter the hourly pay rate for the employees: ";cin >> payRate;cout << "Here is the gross pay for each employee:\n";

for (index = 0; index < 5; index++){

float grossPay = hours[index] * payRate;cout << "Employee #" << (index + 1);cout << ": $" << grossPay << endl;

Enter the hours worked by 5 employees who all

earn the same hourly rate.

Employee #1: 5 [Enter]

Enter the hourly pay rate for all the employees: 12.75 [Enter]

Here is the gross pay for each employee:

Employee #1: $63.75

Employee #2: $127.50

7.8 Arrays As Function Arguments

• To pass an array as an argument to a function, pass the name of the array.

Program 7-13// This program demonstrates that an array element is // passed to a function like any other variable.#include <iostream>using namespace std;

void ShowValue(int Num){

cout << Num << " ";}

int main(){

int collection[8] = {5, 10, 15, 20, 25, 30, 35, 40};for (int Cycle = 0; Cycle < 8; Cycle++)

ShowValue(collection[Cycle]);}

Program Output

5 10 15 20 25 30 35 40

Program 7-14// This program demonstrates an array being passed to a function.#include <iostream>

// Definition of function showValues. This function accepts an array

void showValues(int nums[]){

for (int index = 0; index < 8; index++)cout << nums[index] << " ";

int main(){

int collection[8] = {5, 10, 15, 20, 25, 30, 35, 40};showValues(collection); // Passing address of array collection

Program Output

5 10 15 20 25 30 35 40

Program 7-16// This program uses a function that display the contents // of an integer array of any size.#include <iostream>

void showValues(int nums[], int elements){for (int index = 0; index < elements; index++)

cout << nums[index] << " ";

int main(){int set1[8] = {5, 10, 15, 20, 25, 30, 35, 40};int set2[4] = {2, 4, 6, 8};int set3[12] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};showValues(set1, 8);cout << endl;showValues(set2, 4);cout << endl;showValues(set3, 12);

} C++ Programming, Namiq Sultan 33

Program Output

5 10 15 20 25 30 35 402 4 6 8

1 2 3 4 5 6 7 8 9 10 11 12

Program 7-17

// This program uses a function that doubles the contents // of the elements within an array.#include <iostream>

void doubleArray(int [], int); // Function prototypeconst int arraySize = 12;

int main(){

int set[arraySize] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};cout << "The arrays values are:\n";for (int index = 0; index < arraySize; index++)

cout << set[index] << " ";cout << endl;doubleArray(set, arraySize);cout << "After calling doubleArray, the values are:\n";

for (int index = 0; index < arraySize; index++)cout << set[index] << " ";

cout << endl;}

// Definition of function doubleArray. This function doubles the value of // each element in the array passed into nums. The value passed into size // is the number of elements in the nums array.

void doubleArray(int nums[], int size){

for (int index = 0; index < size; index++)nums[index] *= 2;

Program Output

The array values are:

1 2 3 4 5 6 7 8 9 10 11 12

After calling doubleArray, the values are:

2 4 6 8 10 12 14 16 18 20 22 24

Examples• C++ program to find the largest number in a given array.

• Repeat (1) using a function that accepts an array and returns the largest element.

• C++ program to find the largest two number s in a given array.

• Construct an array of Fibonacci series.

• Sort an array of three elements.

• Reverse the elements of a given array.

• Count the repetition of number 0 in a given array.

• Find the sum of smallest and largest elements of a given array.

7.10 Two-dimensional Arrays

• A two-dimensional array is like several identical arrays put together. It is useful for storing multiple sets of data.

Program 7-18

// This program demonstrates a two-dimensional array.

#include <iostream>

int main(){

float sales[3][4]; // 2D array, 3 rows and 4 columns.float totalSales = 0; // To hold the total sales.int dir, qtr; // Loop counters.

cout << "This program calculate the total sales of\n";cout << "all the company's divisions.\n";cout << "Enter the following sales information:\n\n";

// Nested loops to fill the array with quarterly// sales figures for each division.for (div = 0; div < 3; div++){

for (qtr = 0; qtr < 4; qtr++){

cout << "Division " << (div + 1);cout << ", Quarter " << (qtr + 1) << ": $";cin >> sales[div][qtr];

}cout << endl; // Print blank line.

// Nested loops to add all the elements.for (div = 0; div < 3; div++)

for (qtr = 0; qtr < 4; qtr++)totalSales += sales[div][qtr];

cout << "The total sales for the company are: $";cout << totalSales << endl;

This program will calculate the total sales of

all the company's divisions.

Enter the following sales information:

Division 1, Quarter 1: $31569.45 [Enter]

Output continues

Division 3, Quarter 1: $29654.35 [Enter]Division 3, Quarter 2: $28963.32 [Enter]Division 3, Quarter 3: $25353.55 [Enter]Division 3, Quarter 4: $32615.88 [Enter]

The total sales for the company are: $456782.34

Two-dimensional Array Initialization

• Both of the following declarations perform the same initialization:

int Hours[3][2]={{8,5},{7,9},{6,3}};

int Hours[3][2]={8,5,7,9,6,3};

• It is helpful to write the declaration as:

int Hours[3][2]={ 8,5,

Passing Two-dimensional Arrays to Functions

• When a two-dimensional array is passed to a function, the parameter type must contain a size declarator for the number of columns.

Program 7-19

// This program demonstrates a function that accepts a two-dimensional

// array as an argument.

#include <iostream>

void showArray(int [][4], int); // Function prototype

int main()

int Table[3][4] ={1, 2, 3, 4,

5, 6, 7, 8,

9, 10, 11, 12};

int Table2[4][4] = { 10, 20, 30, 40,

50, 60, 70, 80,

90, 100, 110, 120,

130, 140, 150, 160};

Cout<<“The contents of Table1 are:\n”;

showArray(Table1, 3);

Cout<<“The contents of Table2 are:\n”;

showArray(Table2, 4);

// Function definition for showArray. This function accepts a

// two-dimensional integer array as an argument. The array must have

// four columns. The second argument, Rows, specifies the number of

// rows in the array. The function displays the contents of the array.

void showArray(int Array[][4], int Rows)

for(int x=0; x<Rows; x++)

for(int y=0; y<4; y++)

cout<< Array[x][y] << “\t“;

cout << endl;

}C++ Programming, Namiq Sultan 49

7.10 Arrays of Strings

• A two-dimensional array of characters can be used as an array of C-strings.

Program 7-20

// This program displays the number of days in each month. It uses a two-

// dimensional character array to hold the names of the months and an int array to

// hold the number of days.#include <iostream>

int main(){ char months[12][10] = {"January", "February", "March", "April", "May",

"June", "July", "August", "September”, "October", "November",

"December"};int days[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};for (int count = 0; count < 12; count++){

cout << months[count] << " has ";cout << days[count] << " days.\n";

Program Output

January has 31 days.February has 28 days.March has 31 days.April has 30 days. May has 31 days. June has 30 days. July has 31 days.August has 31 days. September has 30 days. October has 31 days. November has 30 days.December has 31 days.

Three Dimensional Arrays and Beyond

• C++ allows you to create arrays with virtually any number of dimensions.

• Here is an example of a three-dimensional array declaration:

float seat[3][5][8];

Homework• Add two 3x3 matrices and put the result in a third matrix.

• Exchange the elements of first column and second column of a given matrix.

• Find the sum of elements of upper-right triangle of a matrix.

• Print the lower-left triangle of a matrix.

• Write a program to print transpose of a matrix .

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