通常来说,find函数用于寻找某个序列的在string中第一次出现的位置。
find函数有以下四种重载版本:
size_t find (const string& str, size_t pos = 0) const noexcept;
size_t find (const char* s, size_t pos = 0) const;
size_t find (const char* s, size_t pos, size_type n) const;
size_t find (char c, size_t pos = 0) const noexcept;
参数说明:
str/s/c:要寻找的序列,可以是字符串(版本1),也可以是字符串字面值或者说C风格字符串(版本2、3,在版本3中,所寻找的序列是从s[0]开始的前n个字符),也可以是字符(版本4)。
pos:从string的pos位置开始寻找(注意第一个位置是0)。
函数返回序列第一次出现的位置,如果没有找到则返回string::npos。
样例:(摘自cplusplus.com)
#include <iostream> // std::cout
#include <string> // std::string
int main ()
{
std::string str ("There are two needles in this haystack with needles.");
std::string str2 ("needle");
// different member versions of find in the same order as above:
std::size_t found = str.find(str2);
if (found!=std::string::npos)
std::cout << "first 'needle' found at: " << found << '\n';
found=str.find("needles are small",found+1,6);
if (found!=std::string::npos)
std::cout << "second 'needle' found at: " << found << '\n';
found=str.find("haystack");
if (found!=std::string::npos)
std::cout << "'haystack' also found at: " << found << '\n';
found=str.find('.');
if (found!=std::string::npos)
std::cout << "Period found at: " << found << '\n';
// let's replace the first needle:
str.replace(str.find(str2),str2.length(),"preposition");
std::cout << str << '\n';
return 0;
}
标准输出结果:
first 'needle' found at: 14
second 'needle' found at: 44
'haystack' also found at: 30
Period found at: 51
There are two prepositions in this haystack with needles.