C++ Arrays

Key Array Concepts

int arr[5];  // 5 integers

arr[0] = 10;  // first element

int arr[3] = {1, 2, 3};

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

🔹 Array Declaration and Initialization

Arrays in C++ are fixed-size collections declared with a type and size, offering multiple initialization methods. You can list values directly, like int scores[] = {85, 92, 78, 96}, or initialize with strings: char names[] = {"Alice", "Bob", "Charlie"}. These methods allocate contiguous memory, ensuring fast, sequential access. Understanding declaration syntax is foundational for managing data sets, from simple lists to complex buffers, in a memory-efficient manner.

#include <iostream>
using namespace std;

int main() {
    // Method 1: Declare then assign
    int scores[4];
    scores[0] = 85;
    scores[1] = 92;
    scores[2] = 78;
    scores[3] = 96;
    
    // Method 2: Declare and initialize together
    string names[3] = {"Alice", "Bob", "Charlie"};
    
    // Method 3: Let compiler determine size
    double prices[] = {19.99, 25.50, 12.75, 8.99};
    
    cout << "Scores: ";
    for (int i = 0; i < 4; i++) {
        cout << scores[i] << " ";
    }
    cout << endl;
    
    cout << "Names: ";
    for (int i = 0; i < 3; i++) {
        cout << names[i] << " ";
    }
    cout << endl;
    
    return 0;
}

🔹 Accessing Array Elements

Array elements are accessed via zero-based indexing, allowing both reading and modification of values. For a weekly temperature array, you might read temps[0] as 22°C (Monday) and update temps[2] from 28°C to 26°C (Wednesday). You can also iterate to find extremes, like identifying the highest temperature (e.g., 30°C). This direct index-based manipulation is central to algorithms like searching, sorting, and data transformation in C++ programs.

#include <iostream>
using namespace std;

int main() {
    int temperatures[7] = {22, 25, 28, 30, 27, 24, 21};
    
    cout << "Weekly temperatures:" << endl;
    cout << "Monday: " << temperatures[0] << "°C" << endl;
    cout << "Tuesday: " << temperatures[1] << "°C" << endl;
    cout << "Wednesday: " << temperatures[2] << "°C" << endl;
    
    // Modify an element
    temperatures[2] = 26;  // Change Wednesday's temperature
    cout << "Updated Wednesday: " << temperatures[2] << "°C" << endl;
    
    // Find highest temperature
    int highest = temperatures[0];
    for (int i = 1; i < 7; i++) {
        if (temperatures[i] > highest) {
            highest = temperatures[i];
        }
    }
    cout << "Highest temperature: " << highest << "°C" << endl;
    
    return 0;
}

🔹 Array Size and Loops

Determining array size and iterating with loops is essential for processing all elements dynamically. Using sizeof(array)/sizeof(element) calculates the count (e.g., 6). Loops then traverse each item to perform operations like printing elements {5, 10, 15, 20, 25, 30}, computing their sum (105), or finding the average (17.5). This pattern is crucial for tasks like data aggregation, filtering, and applying functions across collections without manual, per-element code.

#include <iostream>
using namespace std;

int main() {
    int numbers[] = {5, 10, 15, 20, 25, 30};
    
    // Calculate array size
    int size = sizeof(numbers) / sizeof(numbers[0]);
    cout << "Array size: " << size << endl;
    
    // Print all elements
    cout << "Array elements: ";
    for (int i = 0; i < size; i++) {
        cout << numbers[i] << " ";
    }
    cout << endl;
    
    // Calculate sum and average
    int sum = 0;
    for (int i = 0; i < size; i++) {
        sum += numbers[i];
    }
    double average = (double)sum / size;
    
    cout << "Sum: " << sum << endl;
    cout << "Average: " << average << endl;
    
    return 0;
}

🔹 Multi-dimensional Arrays

Multi-dimensional arrays, like 2D matrices, organize data in rows and columns for complex representations. Declared as int matrix[3][4], they can store tabular data. Access uses two indices: matrix[row][column], such as retrieving the value 7 from row 1, column 2. These structures are fundamental in graphics, game grids, scientific computations, and any application requiring coordinate-based data access, enabling efficient modeling of layered information.

#include <iostream>
using namespace std;

int main() {
    // 2D array (3 rows, 4 columns)
    int matrix[3][4] = {
        {1, 2, 3, 4},
        {5, 6, 7, 8},
        {9, 10, 11, 12}
    };
    
    cout << "2D Array (Matrix):" << endl;
    for (int row = 0; row < 3; row++) {
        for (int col = 0; col < 4; col++) {
            cout << matrix[row][col] << "\t";
        }
        cout << endl;
    }
    
    // Access specific element
    cout << "Element at row 1, column 2: " << matrix[1][2] << endl;
    
    return 0;
}