C++ int与string的相互转换

1. int转换成string
   to_string函数
   c++11标准增长了全局函数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);

   示例：

// 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. string转换成int
   　Ⅰ、采用标准库中atoi函数,对于其余类型也都有相应的标准库函数，好比浮点型atof(),long型atol()等等
   　
   示例：

   std::string str = "123";
    int n = atoi(str.c_str());
    cout<<n; //123

   Ⅱ、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

学习总结于：https://www.cnblogs.com/smile233/p/8379802.html