pr0910.cpp

practice c++, it is from the book http://www.amazon.com/Schaums-Outline-Programming-John-Hubbard

//  Programming with C++, Second Edition, by John R. Hubbard
//  Copyright McGraw-Hill, 2000
//  Problem 9.10 on page 222
//  Converting Hundu-Arabic numerals to Roman numerals

#include <iostream>
using namespace std;
string Roman(int);

int main()
{ int n;
  do
  { cin >> n;
    cout << n << " = " << Roman(n) << endl;
  } while (n > 0);
}

string Roman(int n)
{ int d3 = n/1000;  // the thousands digit
  string s(d3, 'M');
  n %= 1000;
  int d2 = n/100;  // the hundreds digit
  if (d2 == 9) s += "CM";
  else if (d2 >= 5)
  { s += "D";
    s += string(d2-5, 'C');
  }
  else if (d2 == 4) s += "CD";
  else s += string(d2, 'X');
  n %= 100;
  int d1 = n/10;  // the tens digit
  if (d1 == 9) s += "XC";
  else if (d1 >= 5)
  { s += "L";
    s += string(d1-5, 'X');
  }
  else if (d1 == 4) s += "XL";
  else s += string(d1, 'X');
  n %= 10;
  int d0 = n/1;  // the ones digit
  if (d0 == 9) s += "IX";
  else if (d0 >= 5)
  { s += "V";
    s += string(d0-5, 'I');
  }
  else if (d0 == 4) s += "IV";
  else s += string(d0, 'I');
  return s;
}