String Length in C++

We can get the length of a string using the .size() method like this:

string message = "Hello world";

// Printing the length:
cout << message.size() << endl; // Output: 11

// Changing the message:
message += "!";

// Printing the new length:
cout << message.size() << endl; // Output: 12

Accessing characters from the end:

The length is useful for accessing characters from the end of a string.

Because strings are 0-indexed, the index of the last character is length - 1:

string message = "Hello world";
int length = message.size();

// Printing the last character:
cout << message[length - 1] << endl; // Output: d

// Printing the second to last character:
cout << message[length - 2] << endl; // Output: l

In general, if you want the nth last character, you use message[length - n].

Slicing characters from the end:

The length is also useful for slicing some characters from the end of a string:

string message = "Hello world";
int length = message.size();

// Slicing last 4 characters:
string lastChars = message.substr(length - 4);
cout << lastChars << endl; // Output: orld

// Slicing last 7 characters:
lastChars = message.substr(length - 7);
cout << lastChars << endl; // Output: o world

In general, if you want the last n characters, you use message.substr(length - n).

Assignment
Follow the Coding Tutorial and let's practice with string length!

Hint
Look at the examples above if you get stuck.