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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class RomanToDecimalConverter {
  9.     private static int convertRec(String s) {
  10.         if (s.isEmpty()) return 0;
  11.              if (s.startsWith("M"))  return 1000 + convertRec(s.substring(1));
  12.         else if (s.startsWith("CM")) return 900  + convertRec(s.substring(2));
  13.         else if (s.startsWith("D"))  return 500  + convertRec(s.substring(1));
  14.         else if (s.startsWith("CD")) return 400  + convertRec(s.substring(2));
  15.         else if (s.startsWith("C"))  return 100  + convertRec(s.substring(1));
  16.         else if (s.startsWith("XC")) return 90   + convertRec(s.substring(2));
  17.         else if (s.startsWith("L"))  return 50   + convertRec(s.substring(1));
  18.         else if (s.startsWith("XL")) return 40   + convertRec(s.substring(2));
  19.         else if (s.startsWith("X"))  return 10   + convertRec(s.substring(1));
  20.         else if (s.startsWith("IX")) return 9    + convertRec(s.substring(2));
  21.         else if (s.startsWith("V"))  return 5    + convertRec(s.substring(1));
  22.         else if (s.startsWith("IV")) return 4    + convertRec(s.substring(2));
  23.         else if (s.startsWith("I"))  return 1    + convertRec(s.substring(1));
  24.         throw new IllegalArgumentException("Unexpected roman numerals");
  25.     }
  26.  
  27.     public static int convert(String s) {
  28.         if (s == null || s.isEmpty() || !s.matches("^(M{0,3})(CM|CD|D?C{0,3})(XC|XL|L?X{0,3})(IX|IV|V?I{0,3})$"))
  29.             return -1;
  30.         return convertRec(s);
  31.     }
  32.  
  33.     public static void main (String[] args) {
  34. 	    printRomanToDecimal("XCIX");
  35. 	    printRomanToDecimal("MMMCMXCIX");
  36.  
  37. 	    //common error cases found in other solutions
  38. 	    printRomanToDecimal("IIX");
  39. 	    printRomanToDecimal("IIXX");
  40. 	    printRomanToDecimal("ABC");
  41. 	    printRomanToDecimal("IVX");
  42. 	}
  43.  
  44. 	private static void printRomanToDecimal(String s) {
  45. 	    //change the conversion method accordingly
  46. 	    int decimal = convert(s);
  47. 	    String output = decimal != -1 ? ""+decimal : "Invalid roman numerals";
  48. 	    System.out.println(s + ": " + output);
  49. 	}
  50. }
Success #stdin #stdout 0.04s 711168KB
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stdin
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Standard input is empty
stdout
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XCIX: 99
MMMCMXCIX: 3999
IIX: Invalid roman numerals
IIXX: Invalid roman numerals
ABC: Invalid roman numerals
IVX: Invalid roman numerals
https://ideone.com/YLqqXF
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

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