std::char_traits<char>::find, std::char_traits<wchar_t>::find, std::char_traits<char8_t>::find, std::char_traits<char16_t>::find, std::char_traits<char32_t>::find
From cppreference.com
                    
                                        
                    < cpp | string | char traits
                    
                                                            
                    |   static const char_type* find( const char_type* ptr, std::size_t count, const char_type& ch );  | 
(constexpr since C++17) | |
Searches for character ch within the first count characters of the sequence pointed to by ptr.
See CharTraits for the general requirements on character traits for X::find.
Parameters
| ptr | - | pointer to a character string to search | 
| count | - | the number of characters to analyze | 
| ch | - | the character to search for | 
Return value
A pointer to the first character in the range specified by [ptr, ptr + count) that compares equal to ch, or a null pointer if not found.
Complexity
Linear in count.