String Substrings, Searching (find()), and Modification (replace, erase)0%

Fixed-Size Arrays with std::array vs C-Style Arrays

String Substrings, Searching (find()), and Modification (replace, erase)

Beginner13 min read•Updated: 2026-10-22

🔍 String Substrings, Searching, and Modification

Introduction

Manipulating text requires searching for patterns, extracting tokens, and replacing substrings. std::string offers built-in methods that operate safely without manual memory management.

🔎 Searching with `.find()` and `std::string::npos`

When .find() fails to locate a substring, it returns the sentinel value std::string::npos:

1#include <iostream>
2#include <string>
3 
4int main() {
5    std::string email = "admissions@mskinstitute.in";
6 
7    std::size_t atIndex = email.find('@');
8 
9    if (atIndex != std::string::npos) {
10        std::cout << "'@' found at index: " << atIndex << "\n";
11 
12        // Extracting substring: substr(startIndex, length)
13        std::string username = email.substr(0, atIndex);
14        std::string domain = email.substr(atIndex + 1);
15 
16        std::cout << "Username: " << username << "\n";
17        std::cout << "Domain:   " << domain << "\n";
18    } else {
19        std::cout << "Invalid email: No '@' found.\n";
20    }
21 
22    return 0;
23}

✏️ Modifying Strings: `replace` and `erase`

1#include <iostream>
2#include <string>
3 
4int main() {
5    std::string notice = "Class will take place at Hall 1.";
6 
7    // Erase 4 characters starting at index 25 ("Hall")
8    std::size_t hallPos = notice.find("Hall 1");
9    if (hallPos != std::string::npos) {
10        notice.replace(hallPos, 6, "Lab 4 (Computer Science Wing)");
11    }
12 
13    std::cout << "Updated Notice: " << notice << "\n";
14    return 0;
15}

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Fixed-Size Arrays with std::array vs C-Style Arrays

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std::string Basics: Concatenation, length(), size(), and empty()	Fixed-Size Arrays with std::array vs C-Style Arrays

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Fixed-Size Arrays with std::array vs C-Style Arrays

String Substrings, Searching (find()), and Modification (replace, erase)

Beginner13 min read•Updated: 2026-10-22

Study Materials

🔍 String Substrings, Searching, and Modification

Introduction

Manipulating text requires searching for patterns, extracting tokens, and replacing substrings. std::string offers built-in methods that operate safely without manual memory management.

🔎 Searching with `.find()` and `std::string::npos`

When .find() fails to locate a substring, it returns the sentinel value std::string::npos:

1#include <iostream>
2#include <string>
3 
4int main() {
5    std::string email = "admissions@mskinstitute.in";
6 
7    std::size_t atIndex = email.find('@');
8 
9    if (atIndex != std::string::npos) {
10        std::cout << "'@' found at index: " << atIndex << "\n";
11 
12        // Extracting substring: substr(startIndex, length)
13        std::string username = email.substr(0, atIndex);
14        std::string domain = email.substr(atIndex + 1);
15 
16        std::cout << "Username: " << username << "\n";
17        std::cout << "Domain:   " << domain << "\n";
18    } else {
19        std::cout << "Invalid email: No '@' found.\n";
20    }
21 
22    return 0;
23}

✏️ Modifying Strings: `replace` and `erase`

1#include <iostream>
2#include <string>
3 
4int main() {
5    std::string notice = "Class will take place at Hall 1.";
6 
7    // Erase 4 characters starting at index 25 ("Hall")
8    std::size_t hallPos = notice.find("Hall 1");
9    if (hallPos != std::string::npos) {
10        notice.replace(hallPos, 6, "Lab 4 (Computer Science Wing)");
11    }
12 
13    std::cout << "Updated Notice: " << notice << "\n";
14    return 0;
15}

Next Lesson

Fixed-Size Arrays with std::array vs C-Style Arrays

Continue learning with hands-on practice, examples, and exercises in the upcoming topic.

Related Lessons

Previous Lesson	Next Lesson
std::string Basics: Concatenation, length(), size(), and empty()	Fixed-Size Arrays with std::array vs C-Style Arrays

Practice Quiz

Test your understanding of this lesson with 1 questions. Each question has one correct answer.

Previous Next

🔍 String Substrings, Searching, and Modification

Introduction

🔎 Searching with .find() and std::string::npos

✏️ Modifying Strings: replace and erase

Fixed-Size Arrays with std::array vs C-Style Arrays

Related Lessons

Practice Quiz

Loading Page Content...

🔍 String Substrings, Searching, and Modification

Introduction

🔎 Searching with .find() and std::string::npos

✏️ Modifying Strings: replace and erase

Fixed-Size Arrays with std::array vs C-Style Arrays

Related Lessons

Practice Quiz

🔎 Searching with `.find()` and `std::string::npos`

✏️ Modifying Strings: `replace` and `erase`

🔎 Searching with `.find()` and `std::string::npos`

✏️ Modifying Strings: `replace` and `erase`