Introduction to Arrays

Arrays are a fundamental data structure that store multiple elements of the same type in contiguous memory locations. They offer an efficient way to manage collections of data.

Key Terminologies

• Array Index: Each element in an array is identified by an index, starting from 0.
• Array Element: Individual items stored in an array, accessed using their respective index.
• Array Length: The total number of elements an array can hold.

Memory Representation

Arrays store elements sequentially in memory, which allows for quick access and efficient manipulation.

Declaring an Array

Array declarations vary across programming languages. Below are some C++ examples:

// Integer array
int arr[5];
 
// Character array
char arr[10];
 
// Floating-point array
float arr[20];

Initializing an Array

An array can be initialized at the time of declaration:

int arr[] = {1, 2, 3, 4, 5};
char arr[5] = {'a', 'b', 'c', 'd', 'e'};
float arr[10] = {1.4, 2.0, 24, 5.0, 0.0};

Why Use Arrays?

Managing multiple variables individually can be inefficient. Arrays provide a structured way to store and manipulate large amounts of data efficiently.

Types of Arrays

Based on Size

1. Fixed-Size Arrays

Fixed-size arrays have a predefined length that cannot be modified after allocation.

// Compile-time fixed-size array
int arr[5];
 
// Initialized fixed-size array
int arr2[5] = {1, 2, 3, 4, 5};
 
// Dynamically allocated array
int *arr = new int[5];

2. Dynamic Arrays

Dynamic arrays can grow or shrink during runtime, offering flexibility.

#include <vector>
vector<int> v; // Dynamic integer array

Based on Dimensions

1. One-Dimensional Arrays (1D)

A 1D array stores elements in a linear sequence.

2. Multi-Dimensional Arrays

Multi-dimensional arrays can represent complex structures like tables.

Two-Dimensional Array (2D Matrix)

int matrix[3][3] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};

Three-Dimensional Array (3D)

int array3D[2][2][2] = {{{1,2}, {3,4}}, {{5,6}, {7,8}}};

Array Operations

1. Traversal

Iterating through an array to access its elements.

int arr[] = {10, 20, 30, 40, 50};
for (int i = 0; i < 5; i++) {
    cout << arr[i] << " ";
}

2. Insertion

Adding an element at a specific position requires shifting elements.

int arr[6] = {10, 20, 30, 40, 50};
int pos = 2, value = 25;
 
// Shift elements
for (int i = 5; i > pos; i--) {
    arr[i] = arr[i - 1];
}
arr[pos] = value;

3. Deletion

Removing an element requires shifting remaining elements.

int arr[5] = {10, 20, 30, 40, 50};
int pos = 2;
 
// Shift elements
for (int i = pos; i < 4; i++) {
    arr[i] = arr[i + 1];
}