Strings

std::string

The std::string class represents text strings. Requires #include <string>.

std::string greeting = "Hello";
std::string name("Ana"); // Another way to create a string

Basic operations

std::string a = "Hello";
std::string b = "World";
 
std::string c = a + " " + b;      // Concatenation: "Hello World"
int len = a.size();               // String length (also length())
 
a += "!";                         // Append to end: "Hello!"

Character access

char first = a[0];       // First character (no bounds checking)
char second = a.at(1);   // Second character (throws exception if index doesn't exist)
char last = a.back();    // Last character

Comparison

You can compare directly with ==, !=, <, etc. (lexicographic order):

if (a == b) { /* ... */ }
bool starts = a.starts_with("Ho"); // C++20: starts with "Ho"?
bool ends  = a.ends_with("la");    // C++20: ends with "la"?

Substrings and searching

std::string sub = a.substr(0, 4);      // Substring from position 0, length 4
size_t pos = a.find("World");          // Position of "World", or std::string::npos if not found
std::string replacement = "Hello World";
replacement.replace(5, 5, "C++");      // Replaces from 5, 5 characters => "Hello C++"

Warning

find returns std::string::npos (a huge number) if the substring is not found. Do not compare it directly with -1.

Conversion

int num = std::stoi("42");           // string → int
double d = std::stod("3.14");        // string → double
std::string s = std::to_string(42);  // number → string

Note

std::string is a single class that can grow dynamically. Literals like "Hello" are actually const char* (a character array), but they are implicitly converted to std::string.

Tip

std::string manages its memory automatically (Dynamic Memory and Smart Pointers), so there is no need to free it manually.

Next: Arrays and Vectors