知识点6 C 数据类型转换string，如何实现高效的长尾词转换？

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cpp

一、int 转 string

在 C++11 标准中，增加了全局函数 std::to_string，可以直接将整数转换为字符串：std::string to_string(int val);std::string to_string(long val);std::string to_string(long long val);std::string to_string(unsigned val);std::string to_string(unsigned long val);

一、int转string

1.c++11标准增加了全局函数std::to_string:

string to_string (int val);

string to_string (long val);

string to_string (long long val);

string to_string (unsigned val);

string to_string (unsigned long val);

string to_string (unsigned long long val);

string to_string (float val);

string to_string (double val);

string to_string (long double val);

Example:

// to_string example #include <iostream> // std::cout #include <string> // std::string, std::to_string int main () { std::string pi = "pi is " + std::to_string(3.1415926); std::string perfect = std::to_string(1+2+4+7+14) + " is a perfect number"; std::cout << pi << ‘\n‘; std::cout << perfect << ‘\n‘; return 0; }

　　Output:

pi is 3.141593 28 is a perfect number

　　

二、string转int

1.可以使用std::stoi/stol/stoll等等函数
Example:

// stoi example #include <iostream> // std::cout #include <string> // std::string, std::stoi int main () { std::string str_dec = "2001, A Space Odyssey"; std::string str_hex = "40c3"; std::string str_bin = "-10010110001"; std::string str_auto = "0x7f"; std::string::size_type sz; // alias of size_t int i_dec = std::stoi (str_dec,&sz); int i_hex = std::stoi (str_hex,nullptr,16); int i_bin = std::stoi (str_bin,nullptr,2); int i_auto = std::stoi (str_auto,nullptr,0); std::cout << str_dec << ": " << i_dec << " and [" << str_dec.substr(sz) << "]\n"; std::cout << str_hex << ": " << i_hex << ‘\n‘; std::cout << str_bin << ": " << i_bin << ‘\n‘; std::cout << str_auto << ": " << i_auto << ‘\n‘; return 0; }

　　Output:

2001, A Space Odyssey: 2001 and [, A Space Odyssey] 40c3: 16579 -10010110001: -1201 0x7f: 127