How std::find_last_of actually works?

Question

string s = "I Like C++ Tutorial";
cout << s.find_last_of("Like"); 

I know that find_last_of returns the last character that matches, however, it returns 16, which is the position of the letter i in Tutorial, But I'm confused because I'm searching for the last position of Like not i, I tried to remove i from the string. It returns 5 as I expected. But the question is why did it return 16?

Answer 1

std::find_last_of

Finds the last character equal to one of characters in str

this means when searching the string "I Like C++ Tutorial" for the string "Like" the last character that apears in both strings is "i" wich is at position 16.

when searching for a complete string use std::find

std::string s("I Like C++ Tutorial");
std::cout << s.find("Like"); // prints 2

if you want to find the last occurence of the string use std::rfind

std::string s("I Like C++ Tutorial Like");
std::cout << s.rfind("Like"); // prints 20

to get the position of the last character in the last match you just have to add the length of the string:

std::string s("I Like C++ Tutorial Like");
std::string s2("Like");
std::cout << s.rfind(s2) + s2.length(); // prints 24

Answer 2

find_last_of finds the last character equal to one of characters in the given character sequence.

The character sequence is "Like". The last L is at position 3, the last i is at position 16, the last k is at position 4 and the the last e is at position 5. So it returned the 16, the greatest of these values.

If the character sequence was "like" instead of "Like", it would have returned 18 because the last l is at position 18.

In case no letter in the character sequence that matches any letter in the string, npos is returned.