Array in C++ Programming Language

Lecture Code: CIT 202

Bowen University, Iwo Nigeria

Learning Objectives: Students’ will learn different C++ array programming

statements, structure with sample solutions.

Targeted Students: 200 Level

Course Title: Computer Programming ||

Introduction to Array

An array is a list of elements of the same type

An array is declared by base type (the type of each until of data)

and number of units of memory (how much data).

For instance, 5 values of type int can be stored in an array without having to declare 5 different variables, with each

one having different identifier

The elements, which are placed in a contiguous

memory locations referenced individually by

adding an index.

An Array identified by a pair of square brackets [ ]

Once an array is created, its length is fixed and cannot be changed.

Int scores[10]; // Declare an int array called scores with 10 elements

double averageScore[20]; // Declare an double array of 20 elements

const int Student = 15;

float temps[student]; // Use const int as array length

// Some compilers support using variables for array size, e.g.,int size;cout << "Enter the length of the array: ";cin >> size;float values[size];

Array Declaration

dataType arrayName[arraySize]; // arraySize can be a literal or a variable

// Declare and initialize an int array of 3 elements

int numbers [5] = {11, 33, 44, 55, 66};

// Please note that If an array size is omitted, the compiler counts the elements

int numbers[] = {11, 33, 44, 55, 66};

// Kindly ensure that the number of elements in the initialization shall be equal to or less than length

int numbers[8] = {11, 33, 44, 55, 66}; // Remaining elements are zero. Confusing! Don't do this

int numbers[2] = {11, 33, 44}; // ERROR: too many initializers

// Use {0} or {} to initialize all elements to 0

int numbers[5] = {0}; // First element to 0, the rest also to zero

int numbers[5] = {}; // All element to 0 too

Array Initialization

Elements of an Array

• Arrays have 0 as the first index not 1. In this example, mark[0] is the first element.

• If the size of an array is n, to access the last element, (n-1) index is used. In this

example, mark[4] is the last element.

• Suppose the starting address of mark[0] is 1120d. Then, the next address, mark[1],

will be 1124d, address of mark[2] will be 1128d and so on. It's because the size of

float is 4 bytes.

For Instance: float mark[5];

15 25 35 45 55

mark[0] mark[1] mark[2] mark[3] mark[4]

int mark[5] = {15, 25, 35, 45, 55}

// take input from the user and insert in third elementcin >> mark[2];

// to store the value 55 in the 4th elementmark[3] = 9;

// to pass the value of the 4th element to a variable AA = mark[3] ;

// take input from the user and insert in (i+1)th elementcin >> mark[i];

// print first element of the arraycout << mark[0];

// print ith element of the arraycout >> mark[i-1];

How to access and print array elements?

15 25 35 45 55

mark[0] mark[1] mark[2] mark[3] mark[4]

C++ Multidimensional Arrays

Multidimensional arrays can be described as "arrays of arrays

int x[3][4];

Here, x is a two dimensional array. It can hold a

maximum of 12 elements.

You can think this array as table with 3 rows and

each row has 4 columns.

A two-dimensional array is, in essence, a list of one-dimensional arrays.

sizeof(arrayName) returns the total bytes of the array

Sample C++ Arrays Function

sizeof(arrayName[0]) returns the bytes of first element

At some moment we may need to pass

an array to a function as a parameter.

In C++ it is not possible to pass a

complete block of memory by value as

a parameter to a function, but we are

allowed to pass its address. In practice

this has almost the same effect and it

is a much faster and more efficient

operation.get() :- This function is also used to access the elements of array.

at() :- This function is used to access the elements of array

size() :- It returns the number of elements in array

swap() :- The swap() swaps all elements of one array with other

empty() :- This function returns true when the array size is zero else returns false.

#include <iostream>using namespace std;

int test [] = {6, 25, 7, 40, 12, 71};int i, result=0;

int main (){

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

result += test[i];}cout << result;return 0;

}

#include<iostream>

using namespace std;

int find_largest(int nums[], int n) {

return *max_element(nums, nums + n);

}

int main() {

int nums[] = { 5, 4, 9, 12, 8 };

int n = sizeof(nums) / sizeof(nums[0]);

cout << "Original array:";

for (int i=0; i < n; i++)

cout << nums[i] <<" ";

cout << "\nLargest element of the said array: "<<

find_largest(nums, n);

return 0;

}

Sample Examples One

What is the output of the following array examples?

#include <iostream>using namespace std;

void display(int score[5]);

int main(){

int score[5] = {77, 88, 99, 66, 55};display(score);return 0;

}

void display(int m[5]){

cout << "Displaying Students’ Score: "<< endl;

for (int i = 0; i < 5; ++i){

cout << "Student "<< i + 1 <<": "<< m[i] << endl;}

}

double getAverage(int arr[], int size) {int i, sum = 0; double avg;

for (i = 0; i < size; ++i) {sum += arr[i];

}avg = double(sum) / size;

return avg;}

Displaying Students’ Score: Student 1: 77Student 2: 88Student 3: 99Student 4: 66Student 5: 55

Sample Examples Two

•You cannot return an array from a function. But I will discuss more about arrays and functions in the next lesson.

•You cannot output an array like you output a float or int or char or...

int score[10];cout << score << endl;

• You cannot read into an array, i.e cin >> score;

• If you try to access array elements outside of its bound, let's say score[14], the compiler may not show any

error. However, this may cause unexpected output.

Tips to remember when working with arrays in C++

References

1. Object –Oriented –Programming in C++ by E Balagurusamy. .

2. OO Programming in C++ by Robert Lafore, Galgotia Publications Pvt. Ltd.

3. Object Oriented Programming and C++ By R. Rajaram.

4. Object –Oriented –Programming in C++ by Robert Lafore