cppreference.com > C++ Strings > find_last_of find_last_of Syntax:
      #include <string>
      size_type find_last_of( const string& str, size_type index = npos );
      size_type find_last_of( const char* str, size_type index = npos );
      size_type find_last_of( const char* str, size_type index, size_type num );
      size_type find_last_of( char ch, size_type index = npos );
The find_last_of() function either: returns the index of the first character within the current string that matches any character in str, doing a reverse search from index, string::npos if nothing is found, returns the index of the first character within the current string that matches any character in str, doing a reverse search from index and searching at most num characters, string::npos if nothing is found, or returns the index of the first occurrence of ch in the current string, doing a reverse search from index, string::npos if nothing is found. Related topics: find find_first_not_of find_first_of find_last_not_of rfind