Array Data Structure

Definition

An array is a data structure that stores a collection of elements of the same data type in contiguous memory locations. Each element can be accessed directly using its index position. Arrays have a fixed size that is determined at the time of creation.

Key Properties

Fixed Size

Size is determined at creation and cannot be changed

Contiguous Memory

Elements are stored in adjacent memory locations

Random Access

O(1) time complexity for accessing any element

Same Data Type

All elements must be of the same type

Zero-based Indexing

First element is at index 0

Cache Friendly

Better performance due to spatial locality

Time Complexity

Operation	Time Complexity	Description
Access	O(1)	Direct access by index
Search	O(n)	Linear search through elements
Insertion	O(n)	May require shifting elements
Deletion	O(n)	May require shifting elements
Update	O(1)	Direct update by index

Code Examples

JavaScript

// Array declaration and initialization
let numbers = [1, 2, 3, 4, 5];
let fruits = new Array('apple', 'banana', 'orange');

// Accessing elements
console.log(numbers[0]); // 1
console.log(fruits[1]);  // 'banana'

// Modifying elements
numbers[2] = 10;
console.log(numbers); // [1, 2, 10, 4, 5]

// Array methods
numbers.push(6);        // Add to end
numbers.unshift(0);     // Add to beginning
numbers.pop();          // Remove from end
numbers.shift();        // Remove from beginning

// Iteration
for (let i = 0; i < numbers.length; i++) {
    console.log(numbers[i]);
}

// Modern iteration
numbers.forEach(num => console.log(num));
numbers.map(num => num * 2); // [2, 4, 20, 8, 10]

Python

# List (Python's array equivalent)
numbers = [1, 2, 3, 4, 5]
fruits = ['apple', 'banana', 'orange']

# Accessing elements
print(numbers[0])  # 1
print(fruits[-1])  # 'orange' (last element)

# Modifying elements
numbers[2] = 10
print(numbers)  # [1, 2, 10, 4, 5]

# List methods
numbers.append(6)      # Add to end
numbers.insert(0, 0)   # Insert at index
numbers.remove(10)     # Remove first occurrence
numbers.pop()          # Remove and return last element

# List comprehensions
squares = [x**2 for x in range(5)]  # [0, 1, 4, 9, 16]
evens = [x for x in numbers if x % 2 == 0]

# Iteration
for num in numbers:
    print(num)

# Using enumerate for index
for i, num in enumerate(numbers):
    print(f"Index {i}: {num}")

Java

// Array declaration and initialization
int[] numbers = {1, 2, 3, 4, 5};
String[] fruits = new String[]{"apple", "banana", "orange"};

// Accessing elements
System.out.println(numbers[0]); // 1
System.out.println(fruits[1]);  // "banana"

// Modifying elements
numbers[2] = 10;
System.out.println(Arrays.toString(numbers)); // [1, 2, 10, 4, 5]

// Array length
System.out.println(numbers.length); // 5

// Iteration
for (int i = 0; i < numbers.length; i++) {
    System.out.println(numbers[i]);
}

// Enhanced for loop
for (int num : numbers) {
    System.out.println(num);
}

// Using ArrayList for dynamic arrays
ArrayList<Integer> dynamicArray = new ArrayList<>();
dynamicArray.add(1);
dynamicArray.add(2);
dynamicArray.remove(0); // Remove at index 0

Common Use Cases

Data Storage

Storing collections of similar data

Mathematical Operations

Vectors, matrices, and mathematical computations

Buffer/Queue Implementation

Fixed-size buffers and circular queues

Lookup Tables

Fast access to precomputed values

Image Processing

Pixel data and image manipulation

Algorithm Implementation

Base for many sorting and searching algorithms