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 << ' ';
std::cout << perfect << ' ';
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) << "] ";
std::cout << str_hex << ": " << i_hex << ' ';
std::cout << str_bin << ": " << i_bin << ' ';
std::cout << str_auto << ": " << i_auto << ' ';

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

参考资料：

http://blog.csdn.net/chavo0/article/details/51038397

http://blog.csdn.net/na_beginning/article/details/53576123

原文链接：https://blog.csdn.net/u010510020/article/details/73799996