Arrays and Strings in C++

What are Arrays in C++?

An array is a collection of elements of the same data type, stored in contiguous memory locations.

Key Characteristics:

• Fixed size (defined at the time of declaration).
• Elements can be accessed using an index (starting from 0).
• All elements must be of the same type.

Syntax:

data_type array_name[size];

Example:

#include <iostream>
using namespace std;

int main() {
    int numbers[5] = {10, 20, 30, 40, 50}; // An array of 5 integers

    // Accessing elements using index
    cout << "First element: " << numbers[0] << endl;
    cout << "Last element: " << numbers[4] << endl;
    return 0;
}

Output:

First element: 10
Last element: 50

Why Use Arrays?

• Efficient way to store and access multiple values.
• Allows sequential processing of elements.
• Useful for various algorithms (sorting, searching, etc.).

Types of Arrays in C++

1. One-Dimensional Arrays (1D Arrays)
2. Multi-Dimensional Arrays (2D, 3D, etc.)
3. Character Arrays (Strings)

1. One-Dimensional Arrays

A 1D array is a list of elements stored in a single row.

Example:

#include <iostream>
using namespace std;

int main() {
    int marks[4]; // Declaration of an array

    // Storing values in the array
    marks[0] = 85;
    marks[1] = 90;
    marks[2] = 78;
    marks[3] = 88;

    // Displaying array elements
    for (int i = 0; i < 4; i++) {
        cout << "Marks[" << i << "] = " << marks[i] << endl;
    }
    return 0;
}

Output:

Marks[0] = 85
Marks[1] = 90
Marks[2] = 78
Marks[3] = 88

2. Multi-Dimensional Arrays

A multi-dimensional array is an array of arrays.

2D Arrays (Matrix)

A 2D array can be visualized as a table with rows and columns.

Syntax:

data_type array_name[rows][columns];

Example:

#include <iostream>
using namespace std;

int main() {
    int matrix[2][3] = {
        {1, 2, 3},
        {4, 5, 6}
    };

    // Displaying 2D array elements
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 3; j++) {
            cout << matrix[i][j] << " ";
        }
        cout << endl;
    }
    return 0;
}

Output:

1 2 3 
4 5 6

3. Character Arrays (C-Style Strings)

Character arrays are used to store sequences of characters, also known as C-style strings.

Syntax:

char string_name[size];

Example:

#include <iostream>
using namespace std;

int main() {
    char name[10] = "Hello";
    cout << "String: " << name << endl;
    return 0;
}

Output:

String: Hello

Initialization of Arrays

You can initialize arrays in several ways:

1. Partial Initialization:

int numbers[5] = {1, 2};  // Remaining elements will be 0

2. Automatic Size Detection:

int values[] = {10, 20, 30}; // Size will be automatically set to 3

3. Using Loops:

#include <iostream>
using namespace std;

int main() {
    int arr[5];
    for (int i = 0; i < 5; i++) {
        arr[i] = i * 10;
    }

    for (int i = 0; i < 5; i++) {
        cout << "arr[" << i << "] = " << arr[i] << endl;
    }
    return 0;
}

Output:

arr[0] = 0
arr[1] = 10
arr[2] = 20
arr[3] = 30
arr[4] = 40

Strings in C++

Strings are sequences of characters. C++ provides two main ways to work with strings:

1. C-Style Strings (Character Arrays)
2. C++ String Class (from <string> library)

1. C-Style Strings (Character Arrays)

These are arrays of characters ending with a null character ('\0').

Example:

#include <iostream>
using namespace std;

int main() {
    char text[] = "Welcome to C++";
    cout << "Message: " << text << endl;
    return 0;
}

Output:

Message: Welcome to C++

Common Functions for C-Style Strings:

• strlen() - Length of string.
• strcpy() - Copy one string to another.
• strcat() - Concatenate two strings.
• strcmp() - Compare two strings.

Example:

#include <iostream>
#include <cstring>
using namespace std;

int main() {
    char str1[20] = "Hello";
    char str2[20] = "World";

    strcat(str1, str2);  // Concatenation
    cout << "Concatenated String: " << str1 << endl;
    cout << "Length of str1: " << strlen(str1) << endl;
    return 0;
}

Output:

Concatenated String: HelloWorld
Length of str1: 10

2. C++ String Class (Preferred Method)

C++ provides the string class in the <string> library, making string manipulation easier.

Example:

#include <iostream>
#include <string>
using namespace std;

int main() {
    string name = "Khusboo";
    cout << "Name: " << name << endl;
    cout << "Length: " << name.length() << endl;
    name += " Tayal";
    cout << "Full Name: " << name << endl;
    return 0;
}

Output:

Name: Khusboo
Length: 7
Full Name: Khusboo Tayal

Key String Functions:

• length() - Get the length of the string.
• append() - Add another string.
• substr() - Extract substring.
• find() - Find substring position.
• replace() - Replace part of the string.

Multi-Dimensional Strings

Strings can also be stored in multi-dimensional arrays, useful for handling lists of strings.

Example:

#include <iostream>
#include <string>
using namespace std;

int main() {
    string students[3] = {"Alice", "Bob", "Charlie"};
    for (int i = 0; i < 3; i++) {
        cout << "Student " << (i + 1) << ": " << students[i] << endl;
    }
    return 0;
}

Output:

Student 1: Alice
Student 2: Bob
Student 3: Charlie

Summary

In this tutorial, you learned:

• What arrays are and how to use 1D, 2D, and multi-dimensional arrays.
• How to manipulate C-style strings and C++ strings.
• Common string functions and best practices.