Alternative to itoa() for converting integer to string C++? [duplicate]

Question

In C++11 you can use std::to_string:

#include <string>

std::string s = std::to_string(5);

If you're working with prior to C++11, you could use C++ streams:

#include <sstream>

int i = 5;
std::string s;
std::stringstream out;
out << i;
s = out.str();

Taken from http://notfaq.wordpress.com/2006/08/30/c-convert-int-to-string/

boost::lexical_cast works pretty well.

#include <boost/lexical_cast.hpp>
int main(int argc, char** argv) {
    std::string foo = boost::lexical_cast<std::string>(argc);
}

Archeology

itoa was a non-standard helper function designed to complement the atoi standard function, and probably hiding a sprintf (Most its features can be implemented in terms of sprintf): http://www.cplusplus.com/reference/clibrary/cstdlib/itoa.html

The C Way

Use sprintf. Or snprintf. Or whatever tool you find.

Despite the fact some functions are not in the standard, as rightly mentioned by "onebyone" in one of his comments, most compiler will offer you an alternative (e.g. Visual C++ has its own _snprintf you can typedef to snprintf if you need it).

The C++ way.

Use the C++ streams (in the current case std::stringstream (or even the deprecated std::strstream, as proposed by Herb Sutter in one of his books, because it's somewhat faster).

Conclusion

You're in C++, which means that you can choose the way you want it:

• The faster way (i.e. the C way), but you should be sure the code is a bottleneck in your application (premature optimizations are evil, etc.) and that your code is safely encapsulated to avoid risking buffer overruns.

• The safer way (i.e., the C++ way), if you know this part of the code is not critical, so better be sure this part of the code won't break at random moments because someone mistook a size or a pointer (which happens in real life, like... yesterday, on my computer, because someone thought it "cool" to use the faster way without really needing it).

Try sprintf():

char str[12];
int num = 3;
sprintf(str, "%d", num); // str now contains "3"

sprintf() is like printf() but outputs to a string.

Also, as Parappa mentioned in the comments, you might want to use snprintf() to stop a buffer overflow from occuring (where the number you're converting doesn't fit the size of your string.) It works like this:

snprintf(str, sizeof(str), "%d", num);

Behind the scenes, lexical_cast does this:

std::stringstream str;
str << myint;
std::string result;
str >> result;

If you don't want to "drag in" boost for this, then using the above is a good solution.