C++ string

std::string is the C++ standard-library string type declared in <string>. It manages its character count and storage automatically, making it the usual choice for text instead of manually maintaining a null-terminated character array.

Create, read, and print

A string can be initialized from text and changed by assignment. cin >> text reads one word; use getline(cin, text) when spaces must be preserved.

string language = "C++";
string topic;
getline(cin, topic);
cout << language << ": " << topic << endl;

Length and state

size() and length() both return the number of characters as size_t. empty() reports whether the string contains no characters. None of these operations changes the string.

string text = "Leaflet";
cout << text.size() << endl;   // 7
cout << text.length() << endl; // 7
cout << boolalpha << text.empty() << endl; // false

Access individual characters

text[index] accesses a character with a zero-based index. front() and back() access the first and final characters. at(index) also uses an index but performs bounds checking.

string text = "Leaflet";
cout << text[0] << endl;      // L
cout << text.front() << endl; // L
cout << text.back() << endl;  // t
text[0] = 'l';

Append and insert

append(value) and += add text at the end. insert(position, value) inserts text before a given index. These methods modify the original string.

string text = "Leaf";
text.append("let");       // Leaflet
text += " course";        // Leaflet course
text.insert(7, " C++");   // Leaflet C++ course

Extract, find, and edit

substr(start, count) returns a new string. find(value) returns the starting index of the first match, or string::npos if no match exists. replace(start, count, value) replaces a range, while erase(start, count) removes one.

string text = "Leaflet course";
string name = text.substr(0, 7); // Leaflet
size_t position = text.find("course"); // 8

if (position != string::npos) {
    text.replace(position, 6, "lab"); // Leaflet lab
}

text.erase(7, 4); // Leaflet

Compare strings

== and != test content equality. compare() returns a negative value, zero, or a positive value when the current string sorts before, equals, or sorts after its argument.

string first = "apple";
string second = "banana";

if (first != second && first.compare(second) < 0) {
    cout << first << " comes first" << endl;
}