字符串转数字/数字转字符串模板

std::string to_string(int value); (1) (C++11起)
std::string to_string(long value); (2) (C++11起)
std::string to_string(long long value); (3) (C++11起)
std::string to_string(unsigned value); (4) (C++11起)
std::string to_string(unsigned long value); (5) (C++11起)
std::string to_string(unsigned long long value); (6) (C++11起)
std::string to_string(float value); (7) (C++11起)
std::string to_string(double value); (8) (C++11起)
std::string to_string(long double value); (9) (C++11起)

string i2s(int num)
{
    stringstream stream;
    string result;
 
    stream << num;  // 将int输入流
    stream >> result;  // 从stream中抽取前面插入的int值
  	
    return result;
}

int s2l(string str)
{
    stringstream stream;
    int res;
    
    stream << str;
    stream >> res;
    
    return res;
}