C++ convert int to string

First: output

#include <sstream>

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

Second: C++ function  itoa(int, buffer,num)

 #include <stdio.h>
#include <stdlib.h>

int main ()
{
  int i;
  char buffer [33];
   printf ("Enter a number: ");
  scanf ("%d",&i);
  itoa (i,buffer,10);
  printf ("decimal: %s\n",buffer);
   itoa (i,buffer,16);
  printf ("hexadecimal: %s\n",buffer);
  itoa (i,buffer,2);
  printf ("binary: %s\n",buffer);
  return 0;
 }