知识点6 C++数据类型转换 string

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

巴特西

知识点6 C++数据类型转换 string

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