Useful string methods in C++ 〰️

Metadata

• Date :: 11-04-2025
• Tags :: cpp

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Notes

Detailed Explanation of Useful String Methods in C++

In this tutorial, we explore some common and useful string methods in C++ that help in manipulating strings. These methods allow you to check the length, append strings, manipulate specific characters, and more. Let’s go through each method explained in the video.

1. length() Method

The length() method returns the length (i.e., the number of characters) of a string. This method is particularly useful when you need to check the size of a string before performing operations on it.

Example:

string name;
cout << "Enter your name: ";
getline(cin, name);  // Using getline to allow spaces in the name
 
if (name.length() > 12) {
    cout << "Your name can't be over 12 characters long." << endl;
} else {
    cout << "Welcome, " << name << "!" << endl;
}
 

• Explanation:
  • The program uses the length() method to get the number of characters in the input string name.
  • If the length exceeds 12 characters, it prints a message saying the name can’t be longer than 12 characters.
  • Otherwise, it displays a welcome message with the user’s name.

Sample Input and Output:

• Input: John Doe
  • Output: Welcome, John Doe!
• Input: ThisIsAVeryLongName
  • Output: Your name can't be over 12 characters long.

2. empty() Method

The empty() method checks if a string is empty. It returns a boolean value (true if the string is empty, and false if it contains any characters).

Example:

string name;
cout << "Enter your name: ";
getline(cin, name);
 
if (name.empty()) {
    cout << "You didn't enter your name." << endl;
} else {
    cout << "Hello, " << name << "!" << endl;
}
 

• Explanation:
  • The empty() method is used to check if the string name is empty.
  • If the user doesn’t enter any name, it prints a message saying “You didn’t enter your name.”
  • Otherwise, it greets the user with “Hello, [name]!”

Sample Input and Output:

• Input: (empty string)
  • Output: You didn't enter your name.
• Input: Alice
  • Output: Hello, Alice!

3. clear() Method

The clear() method removes all characters from the string, effectively making it an empty string.

Example:

string name = "John";
cout << "Hello, " << name << endl;
name.clear();
cout << "Name cleared: " << name << endl;
 

• Explanation:
  • Initially, the string name contains "John".
  • The clear() method is called, which empties the string.
  • After clearing, the string name is empty, and attempting to print it shows no output.

Sample Output:

• Output:

  Hello, John
  Name cleared:
  
  

4. append() Method

The append() method adds a string to the end of another string. This is useful when you want to concatenate two strings.

Example:

string name;
cout << "Enter your name: ";
getline(cin, name);
 
name.append("@gmail.com");  // Appending domain to the name
cout << "Your username is now " << name << endl;
 

• Explanation:
  • The append() method adds "@gmail.com" to the string name, creating an email-like username.

Sample Input and Output:

• Input: John
  • Output: Your username is now John@gmail.com

5. at() Method

The at() method allows you to access a character at a specific position in a string. It is safer than directly using array-style indexing because it checks bounds and throws an exception if the index is out of range.

Example:

string name;
cout << "Enter your name: ";
getline(cin, name);
 
cout << "First character: " << name.at(0) << endl;
cout << "Second character: " << name.at(1) << endl;
 

• Explanation:
  • The at() method is used to access characters in the string.
  • name.at(0) returns the first character in the string, while name.at(1) returns the second character.

Sample Input and Output:

• Input: Alice

  • Output:

    First character: A
    Second character: l
    
    

6. insert() Method

The insert() method allows you to insert a substring or a single character at a specified position in the string.

Example:

string name = "Alice";
name.insert(0, "@");  // Insert '@' at the beginning
cout << "Modified name: " << name << endl;
 

• Explanation:
  • The insert() method is used to insert a character at the beginning of the string name.
  • The first argument 0 represents the position (index) where the insertion should happen.

Sample Output:

• Output: Modified name: @Alice

7. find() Method

The find() method searches for a character or substring within the string and returns its index position. If the character is not found, it returns string::npos.

Example:

string name;
cout << "Enter your name: ";
getline(cin, name);
 
size_t pos = name.find(" ");  // Find first space
if (pos != string::npos) {
    cout << "First space at index: " << pos << endl;
} else {
    cout << "No spaces found!" << endl;
}
 

• Explanation:
  • The find() method searches for the first occurrence of a space (" ") in the string name.
  • It returns the index position of the first space, or string::npos if no space is found.

Sample Input and Output:

• Input: John Doe
  • Output: First space at index: 4

8. erase() Method

The erase() method removes a portion of the string. You provide the starting index and the number of characters to erase.

Example:

string name;
cout << "Enter your name: ";
getline(cin, name);
 
name.erase(0, 3);  // Erase first 3 characters
cout << "Name after erasing: " << name << endl;
 

• Explanation:
  • The erase() method removes characters starting from index 0 (the first character) for 3 characters.

Sample Output:

• Input: John Doe
  • Output: Name after erasing: n Doe

Conclusion

These string methods are extremely useful for manipulating and handling strings in C++. Here’s a quick summary of the methods covered:

• length(): Returns the length of the string.
• empty(): Checks if the string is empty.
• clear(): Clears all characters from the string.
• append(): Adds a string to the end of another string.
• at(): Returns the character at a given index (safe access).
• insert(): Inserts a character or substring at a specified position.
• find(): Finds the index of a character or substring.
• erase(): Erases a portion of the string from a given position.

These methods are foundational for string manipulation and can be combined in various ways to solve complex text-related problems.

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References

• Video
• C++ tutorial for beginners 👨‍💻