c++stringtype-conversioninteger

How to convert int to string in C++?

How can I convert from int to the equivalent string in C++? I am aware of two methods. Is there another way?

(1)

int a = 10;
char *intStr = itoa(a);
string str = string(intStr);

(2)

int a = 10;
stringstream ss;
ss << a;
string str = ss.str();
Solution

  • You can use std::to_string available in C++11 as suggested by Matthieu M.:

    std::string s = std::to_string(42);

    Or, if performance is critical (for example, if you do lots of conversions), you can use fmt::format_int from the {fmt} library to convert an integer to std::string:

    std::string s = fmt::format_int(42).str();

    Or a C string:

    fmt::format_int f(42);
const char* s = f.c_str();

    The latter doesn't do any dynamic memory allocations and is more than 70% faster than libstdc++ implementation of std::to_string on Boost Karma benchmarks. See Converting a hundred million integers to strings per second for more details.

    Disclaimer: I'm the author of the {fmt} library.