string (1)  
size_t find_first_of (const string& str, size_t pos = 0) const noexcept;
c-string (2)    
size_t find_first_of (const char* s, size_t pos = 0) const;
buffer (3)  
size_t find_first_of (const char* s, size_t pos, size_t n) const;
character (4)   
size_t find_first_of (char c, size_t pos = 0
 
) const noexcept;

find_first_of函式：在母串上從指定位置開始查詢，如果遇到的字元與目標串中任意字元相同，則查詢成功，返回該字元的位置。

string (1)  
size_t find (const string& str, size_t pos = 0) const noexcept;
c-string (2)    
size_t find (const char* s, size_t pos = 0) const;
buffer (3)  
size_t find (const char* s, size_t pos, size_type n) const
 
;
character (4)   
size_t find (char c, size_t pos = 0) const noexcept;

find函式：在母串上從指定位置開始，查詢字元或字串。當查詢字串時，要保證目標串為母串的子串。下面是cplusplus.com中的描述：

Notice that unlike member find_first_of, whenever more than one character is being searched for, it is not enough that just one of these characters match, but the entire sequence must match.

注：rfind與find使用方法類似；find_last_of、find_first_not_of、find_last_not_of與find_first_of使用方法類似。