Programming

#include <iostream>
#include <string>

using namespace std;

int main ()
{
  const string hexdigits = "0123456789ABCDEF";    //All possible hex digits
  cout << "Enter a series of numbers between 0 and 15"
    << " separated by spaces.\nHit ENTER when finished: " << endl;

  string result;        //will hold the resulting hexify-ed string
  string::size_type n;        //hold numbers from the input

  while (cin >> n)
    if (n < hexdigits.size())    //ignore invalid input
      result += hexdigits[n];    //fetch the individual hex digit

  cout << "Your hex number is: " << result << endl;
  return 0;
}

// https://stackoverflow.com/questions/19307979/cin-in-a-while-loop
#include <iostream>
#include <string>
#include <sstream>

using namespace std;

int main ()
{
  const string hexdigits = "0123456789ABCDEF";

  cout <<  "Enter a series of numbers between 0 and 15"
       << " separated by spaces. Hit ENTER when finished: "
       << endl;

  string line;
  string result;

  if (getline (cin, line))    // get the whole line
    {
      istringstream iss(result);    // break them by spaces
      int i;
      while (iss >> i)
    {
      result += hexdigits[i];
      result += " ";
    }
      cout << "Your hex result:  " << result << endl;
    }
  else
    {
      cout << "Error handling input!" << endl;
    }

  return 0;
}

istringstream iss(result);  // break them by spaces, Wrong code!!
istringstream iss(line);    //This gave me what I expected.