Working with One Dimensional Array in C++

In this lesson, you will learn

• Introduction to Array
• Key features of an Array
• Single Dimensional Array
• Passing an Array to a Function
• Array of Pointers

Introduction to Array

• An array is a group of similar types of variables stored in a contiguous memory location that are referred to by a common name.
• Arrays of any type (i.e. objects also) can be created and may have one or more dimensions.
• The elements of an array are accessed using indices, with the first element being at index 0.
• Arrays are useful for storing collections of data where you want to perform similar operations on each element.

The following Figure shows an integer array called c, containing 12 elements.

Any one of these elements may be referred to by giving the array’s name followed by the position number of the particular element in square brackets ([]).

The first element in every array is the zeroth element (i.e., the one with position number 0).

An array name, like other identifiers, can contain only letters, digits and underscores and cannot begin with a digit.

Key Features of Arrays in Java

1. Fixed Size: Once an array is created, its size cannot be changed. You must know the size of the array in advance.
2. Homogeneous Elements: All elements in a Java array must be of the same type, such as all int, all double, etc.
3. Indexed Access: Elements in an array are accessed by their index, with the first element at index 0.

Types of Arrays

Arrays in Java can be of the following types

Declaring 1-D Arrays

Syntax:

type arrayName[arraySize];

• type: The data type of the elements (e.g., int, float, char, etc.).
• arrayName: The name of the array.
• arraySize: The number of elements the array can hold.

Examples

1. Integer Array:

int numbers[5]; // Declares an array of 5 integers

2. Float Array:

float decimals[3]; // Declares an array of 3 floating-point numbers

3. Character Array:

char letters[4]; // Declares an array of 4 characters

Initializing Arrays

Arrays can be initialized at the time of declaration.

1. Integer Array Initialization:

int numbers[5] = {1, 2, 3, 4, 5}; // Initializes all 5 elements

2. Float Array Initialization:

float decimals[3] = {1.1, 2.2, 3.3}; // Initializes all 3 elements

3. Character Array Initialization:

char letters[4] = {'a', 'b', 'c', 'd'}; // Initializes all 4 elements

Accessing The Array Elements

You can access array elements using their indices.

Example: Accessing Array Elements

#include<iostream>
using namespace std;

int main() {
    int numbers[5] = {1, 2, 3, 4, 5};
    
    // Accessing elements
    cout << "First element: " << numbers[0] << endl; // Output: 1
    cout << "Third element: " << numbers[2] << endl; // Output: 3

    return 0;
}

Example Programs on Array

1. Sum of Array Elements:

#include<iostream>
using namespace std;

int main() {
    int numbers[5] = {10, 20, 30, 40, 50};
    int sum = 0;

    // Calculating the sum of all elements
    for(int i = 0; i < 5; i++) {
        sum += numbers[i];
    }

    cout << "Sum of all elements: " << sum << endl; // Output: 150

    return 0;
}

2. Finding the Maximum Element in an Array:

#include<iostream>
using namespace std;

int main() {
    int numbers[5] = {10, 20, 50, 40, 30};
    int max = numbers[0];

    // Finding the maximum element
    for(int i = 1; i < 5; i++) {
        if(numbers[i] > max) {
            max = numbers[i];
        }
    }

    cout << "Maximum element: " << max << endl; // Output: 50

    return 0;
}

3. Reverse an Array:

#include<iostream>
using namespace std;

int main() {
    int numbers[5] = {1, 2, 3, 4, 5};
    
    // Reversing the array
    for(int i = 0; i < 5 / 2; i++) {
        int temp = numbers[i];
        numbers[i] = numbers[5 - 1 - i];
        numbers[5 - 1 - i] = temp;
    }

    // Displaying the reversed array
    cout << "Reversed array: ";
    for(int i = 0; i < 5; i++) {
        cout << numbers[i] << " ";
    }
    cout << endl;

    return 0;
}

These examples illustrate how to declare, initialize, access, and manipulate arrays in C++. Arrays are fundamental structures in C++ that provide a way to store and operate on a fixed-size sequential collection of elements of the same type.

Passing an Array to The Function

In C++, you can pass any array to a function by using the following methods

1. Passing an Array by Pointer

When you pass an array by pointer, you are essentially passing the address of the first element of the array.

#include 

void printArray(int* arr, int size) {
    for (int i = 0; i < size; ++i) {
        std::cout << arr[i] << " ";
    }
    std::cout << std::endl;
}

int main() {
    int arr[] = {1, 2, 3, 4, 5};
    int size = sizeof(arr) / sizeof(arr[0]);
    printArray(arr, size);
    return 0;
}

Output:

1 2 3 4 5 

2. Passing a Fixed-Size Array by Reference

#include 

// Function to print an array by reference
void printArray(int (&arr)[5]) {
    for (int i = 0; i < 5; ++i) {
        std::cout << arr[i] << " ";
    }
    std::cout << std::endl;
}

int main() {
    int arr[5] = {1, 2, 3, 4, 5}; // Fixed-size array
    printArray(arr); // Passing array by reference
    return 0;
}

Output:

1 2 3 4 5 

Pointer to an Array

When you declare an array, the array name represents the address of the first element of the array. You can use a pointer to access and manipulate array elements.

Example 1: Pointer to an Array

#include<iostream>
using namespace std;

int main() {
    int arr[5] = {10, 20, 30, 40, 50};
    int *ptr = arr; // Pointer to the first element of the array

    // Accessing array elements using the pointer
    for (int i = 0; i < 5; i++) {
        cout << "Element " << i << ": " << *(ptr + i) << endl;
    }

    return 0;
}

Explanation

• int *ptr = arr; assigns the address of the first element of arr to the pointer ptr.
• *(ptr + i) is used to access the elements of the array.

Example 2: Pointer Arithmetic

Pointer arithmetic allows you to navigate through the array elements using a pointer.

#include<iostream>
using namespace std;

int main() {
    int arr[5] = {10, 20, 30, 40, 50};
    int *ptr = arr;

    // Incrementing the pointer to traverse the array
    for (int i = 0; i < 5; i++) {
        cout << "Element " << i << ": " << *ptr << endl;
        ptr++; // Move the pointer to the next element
    }

    return 0;
}

Explanation

• The pointer ptr is incremented (ptr++) to point to the next element in the array.
• *ptr is used to access the value at the current pointer location.

Example 3: Array of Pointers

You can also have an array of pointers, where each pointer points to an element in an array or different arrays.

#include<iostream>
using namespace std;

int main() {
    int arr1[3] = {1, 2, 3};
    int arr2[3] = {4, 5, 6};
    int arr3[3] = {7, 8, 9};

    int *ptrArr[3] = {arr1, arr2, arr3}; // Array of pointers

    // Accessing elements using the array of pointers
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 3; j++) {
            cout << "Element [" << i << "][" << j << "]: " << ptrArr[i][j] << endl;
        }
    }

    return 0;
}

Explanation

• int *ptrArr[3] = {arr1, arr2, arr3}; creates an array of pointers where each element points to the beginning of an array (arr1, arr2, arr3).
• ptrArr[i][j] is used to access the elements of the arrays.

End of the lesson….enjoy learning

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