C++11 std::to_string

一般常用的转换字符串的方法std::stringstream,但是效率较低;目前C ++11提供了std::to_string

效率方面:C风格的sprintf()没有动态分配内存效率最高;std::to_string其次;std::stringstream效率最差
从C++17开始,std::to_string的效率将不差于sprintf,同时有类型更安全的转换函数std::to_char

函数重载原型
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);

#include 
#include  // std::to_string
#include  // std::stringstream

int main()
{
	// old method
	std::stringstream ss;
	ss << 1.23;
	std::string str = ss.str();
	std::cout << str << std::endl;
	// new method
	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 << std::endl;
	std::cout << perfect << std::endl;

	return 0;
}