Strings in C++

Hey there! In this guide, we'll explore how to work with strings in C++. Strings are used to store sequences of characters and are a vital part of any C++ program. Let's dive in!

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1. C-Style Strings

C++ inherits its basic string handling capabilities from C, known as C-style strings. These are arrays of characters terminated by a null character (\0).

Example:

#include <iostream>
using namespace std;

int main() {
    char greeting[] = "Hello";
    cout << greeting << endl;
    return 0;
}

Output:

Hello

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2. C++ String Class

C++ provides a more convenient way to handle strings through the std::string class, which is part of the C++ Standard Library.

Example:

#include <iostream>
#include <string> // Required for string
using namespace std;

int main() {
    string greeting = "Hello, World!";
    cout << greeting << endl;
    return 0;
}

Output:

Hello, World!

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3. Common String Operations

3.1 String Length

You can use the .length() or .size() method to get the length of a string.

Example:

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

int main() {
    string greeting = "Hello, World!";
    cout << "Length: " << greeting.length() << endl;
    return 0;
}

Output:

Length: 13

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3.2 String Concatenation

You can concatenate two strings using the + operator or the .append() method.

Example:

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

int main() {
    string firstName = "John";
    string lastName = "Doe";
    string fullName = firstName + " " + lastName;
    cout << fullName << endl;
    return 0;
}

Output:

John Doe

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3.3 Accessing Characters in a String

You can access individual characters in a string using array-like indexing.

Example:

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

int main() {
    string greeting = "Hello";
    cout << greeting[0] << endl; // Output: H
    return 0;
}

Output:

H

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4. Modifying Strings

4.1 Changing Characters

You can modify individual characters in a string using array-like indexing.

Example:

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

int main() {
    string greeting = "Hello";
    greeting[0] = 'J';
    cout << greeting << endl; // Output: Jello
    return 0;
}

Output:

Jello

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4.2 Substrings

You can extract a substring from a string using the .substr() method.

Example:

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

int main() {
    string greeting = "Hello, World!";
    string sub = greeting.substr(0, 5); // Extracts "Hello"
    cout << sub << endl;
    return 0;
}

Output:

Hello

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4.3 String Comparison

You can compare two strings using the comparison operators (==, !=, >, <, etc.) or the .compare() method.

Example:

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

int main() {
    string str1 = "Hello";
    string str2 = "World";

    if (str1 == str2) {
        cout << "Strings are equal" << endl;
    } else {
        cout << "Strings are not equal" << endl;
    }

    return 0;
}

Output:

Strings are not equal

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5. String Input

You can input strings from the user using cin and getline().

5.1 Using cin

cin stops reading input at the first space.

Example:

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

int main() {
    string name;
    cout << "Enter your name: ";
    cin >> name;
    cout << "Hello, " << name << endl;
    return 0;
}

Output:

Enter your name: John
Hello, John

5.2 Using getline()

getline() reads the entire line, including spaces.

Example:

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

int main() {
    string name;
    cout << "Enter your full name: ";
    getline(cin, name);
    cout << "Hello, " << name << endl;
    return 0;
}

Output:

Enter your full name: John Doe
Hello, John Doe

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6. String Functions

C++ provides several functions to manipulate strings. Some of the most common ones are:

6.1 find()

Finds the first occurrence of a substring.

Example:

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

int main() {
    string str = "Hello, World!";
    size_t pos = str.find("World");

    if (pos != string::npos) {
        cout << "Found at position: " << pos << endl;
    } else {
        cout << "Not found!" << endl;
    }

    return 0;
}

Output:

Found at position: 7

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6.2 replace()

Replaces part of the string with another string.

Example:

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

int main() {
    string str = "Hello, World!";
    str.replace(7, 5, "Universe");
    cout << str << endl;
    return 0;
}

Output:

Hello, Universe!

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Strings are an essential part of C++ programming, and mastering them will greatly improve your ability to handle text and input in your programs. Happy coding!