std::basic_string::rfind

size_type rfind( const basic_string& str, size_type pos = npos ) const;	(1)
size_type rfind( const CharT* s, size_type pos, size_type count ) const;	(2)
size_type rfind( const CharT* s, size_type pos = npos ) const;	(3)
size_type rfind( CharT ch, size_type pos = npos ) const;	(4)
size_type rfind( std::basic_string_view<CharT, Traits> sv, size_type pos = npos) const;	(5)	(since C++17)

查找最后一个子字符串，该子字符串等于给定的字符序列。搜索开始于pos，即发现的子字符串不能以下面的位置开始。pos.如果npos或任何不小于size()-1作为pos，整个字符串将被搜索。

1%29找到最后一个等于str%28相等性是通过调用特征：情商%29，似乎rfind(std::basic_string_view<CharT, Traits>(str), pos)%28自C++17%29

2%29查找最后一个子字符串，该子字符串与第一个子字符串相同。count所指向的字符串的字符。s...s可以包含空字符。相当于rfind(std::basic_string(s, count), pos)%28直到C++17%29rfind(std::basic_string_view<CharT, Traits>(s, count), pos)%28自C++17%29

3%29查找最后一个子字符串，该子字符串等于s字符串的长度由第一个空字符决定。相当于rfind(std::basic_string(s), pos)%28直到C++17%29rfind(std::basic_string_view<CharT, Traits>(s), pos)%28自C++17%29

4%29找到最后一个字符ch相当于rfind(std::basic_string(1,c),pos)

5%29查找最后一个子字符串，该子字符串等于sv

参数

str	-	string to search for
pos	-	position at which to begin searching
count	-	length of substring to search for
s	-	pointer to a character string to search for
ch	-	character to search for
sv	-	std::basic_string_view to search for

返回值

找到的子字符串或npos如果找不到这样的子字符串。注意，这是一个从字符串开始的偏移，而不是结束。

如果size()是零，npos总是会被归还。

如果搜索空字符串%28str.size()，，，count，或strlen(s)为零%29返回pos%28空字符串立即找到%29，除非pos == npos，在这种情况下返回size()...

例外

1-4) (none)	(until C++11)
1,4) noexcept specification: noexcept 2,3) (none)	(since C++11)(until C++14)
1) noexcept specification: noexcept 2,3,4) (none)	(since C++14)
5) noexcept specification: noexcept	(since C++17)

例

二次

#include <string>
#include <iostream>
 
void print(std::string::size_type n, std::string const &s)
{
    if (n == std::string::npos) {
        std::cout << "not found\n";
    } else {
        std::cout << "found: \"" << s.substr(n) << "\" at " << n << '\n';
    }
}
 
int main()
{
    std::string::size_type n;
    std::string const s = "This is a string";
 
    // search backwards from end of string
    n = s.rfind("is");
    print(n, s);
    // search backwards from position 4
    n = s.rfind("is", 4);
    print(n, s);
    // find a single character
    n = s.rfind('s');
    print(n, s);
    // find a single character
    n = s.rfind('q');
    print(n, s);
}

二次

产出：

二次

found: "is a string" at 5
found: "is is a string" at 2
found: "string" at 10
not found

二次

另见

find	find characters in the string (public member function)
find_first_of	find first occurrence of characters (public member function)
find_first_not_of	find first absence of characters (public member function)
find_last_of	find last occurrence of characters (public member function)
find_last_not_of	find last absence of characters (public member function)

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最后更新于：2017-12-18