from:https://www.cnblogs.com/smile233/p/8379802.html

一、int转换成string

Ⅰ、to_string函数

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 

附：to_string()函数的实现

string to_String(int n)//int to string
 {
 	int max=50;
     int m = n;
     char s[max];
     char ss[max];
     int i=0,j=0;
     if (n < 0)// 处理负数
     {
         m = 0 - m;
         j = 1;
         ss[0] = '-';
     }    
     while (m>0)
     {
         s[i++] = m % 10 + '0';
         m /= 10;
     }
     s[i] = '\0';
     i = i - 1;
     while (i >= 0)
     {
         ss[j++] = s[i--];
     }    
     ss[j] = '\0';    
     return ss;
 }