#include <string>
  size_type rfind( const string& str, size_type index );
  size_type rfind( const char* str, size_type index );
  size_type rfind( const char* str, size_type index, size_type num );
  size_type rfind( char ch, size_type index );

The rfind() function either:

• returns the location of the first occurrence of str in the current string, doing a reverse search from index, string::npos if nothing is found,
• returns the location of the first occurrence of str in the current string, doing a reverse search from index, searching at most num characters, string::npos if nothing is found,
• or returns the location of the first occurrence of ch in the current string, doing a reverse search from index, string::npos if nothing is found.

For example, in the following code, the first call to rfind() returns string::npos, because the target word is not within the first 8 characters of the string. However, the second call returns 9, because the target word is within 20 characters of the beginning of the string.

   int loc;
   string s = "My cat's breath smells like cat food.";
   loc = s.rfind( "breath", 8 );
   cout << "The word breath is at index " << loc << endl;
   loc = s.rfind( "breath", 20 );
   cout << "The word breath is at index " << loc << endl;