C++ · Chapter 12 of 49
C++ String Functions
The std::string class provides useful member functions such as `.length()`, `.substr()`, `.find()`, and `.append()`. These let you inspect and transform text without manual loops.
For case conversion or trimming, you'll often combine `<algorithm>` with a lambda, since std::string itself doesn't have built-in upper/lower methods.
Common methods
`.length()`/`.size()` return character count, `.substr(pos, len)` extracts a piece, `.find(str)` returns the index of the first match or `std::string::npos` if not found.
Modifying strings
`.append()` or `+=` add text to the end; `.replace()` swaps a range for new text; `.erase()` removes characters.
Example 1 (cpp)
std::string s = "Hello World";
std::cout << s.substr(6, 5);Output
Worldsubstr(6, 5) extracts 5 characters starting at index 6.
Example 2 (cpp)
std::string s = "Hello";
if (s.find("ell") != std::string::npos)
std::cout << "found";Output
foundfind() returns npos if the substring isn't present.
Key points
- length()/size() return the character count.
- substr(pos, len) extracts a substring.
- find() returns std::string::npos if not found.
- append(), replace(), erase() modify strings.
💡 Note: Always compare find()'s result against std::string::npos, not -1, for correctness.