C++中int与string的相互转换

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
*/

2.采用sstream中定义的字符串流对象来实现

ostringstream os; //构造一个输出字符串流，流内容为空 
int i = 12; 
os << i; //向输出字符串流中输出int整数i的内容 
cout << os.str() << endl; //利用字符串流的str函数获取流中的内容 

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

*/

2.采用标准库中atoi函数,对于其他类型也都有相应的标准库函数，比如浮点型atof(),long型atol()等等

string s = "12"; 
int a = atoi(s.c_str());

3.采用sstream头文件中定义的字符串流对象来实现转换

istringstream is("12"); //构造输入字符串流，流的内容初始化为“12”的字符串 
int i; 
is >> i; //从is流中读入一个int整数存入i中

另一篇博文：string 与 char* 互相转换