[Text] Re: Roman number conversion to Integer

[Gilles Sadowski <gi...@gmail.com>]

IMO it is a [Text] feature (hence the prefix added to the "Subject: " line).

Regards,
Gilles

Le ven. 28 mai 2021 à 08:21, Miguel Munoz
<sw...@yahoo.com.invalid> a écrit :
>
> Here's one take on the problem:
>  /**
>  * <p>Created by IntelliJ IDEA.
>  * <p>Date: 2/4/21
>  * <p>Time: 1:36 AM
>  *
>  * @author Miguel Mu\u00f1oz
>  */
> public class ToRomans {
>   private static int[] divisors = {1000, 500, 100, 50, 10, 5, 1};
>   private static char[] romans = {'M', 'D', 'C', 'L', 'X', 'V', 'I'};
>
>   /**
>    * Convert a positive, non-zero integer to Roman numerals.
>    * Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead,
>    * the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to
>    * the number nine, which is written as IX. There are six instances where subtraction is used:
>    *
>    * I can be placed before V (5) and X (10) to make 4 and 9.
>    * X can be placed before L (50) and C (100) to make 40 and 90.
>    * C can be placed before D (500) and M (1000) to make 400 and 900.
>    *
>    * Zero cannot be expressed in Roman numerals. The Romans never invented zero. (Yeah. I'm serious.)
>    * @param num The number to convert
>    * @return A string expressing the number in Roman numerals
>    */
>   public String intToRoman(final int num) {
>     if ((num < 1) || (num > 3999)) {
>       throw new IllegalArgumentException(String.format("Value %d is out of range (1 - 3999)", num));
>     }
>     int val = num;
>     StringBuilder builder = new StringBuilder();
>     for (int i = 0; i < divisors.length; i += 2) {
>       int mod = divisors[i];
>       int v = val / mod;
>       if (v > 0) {
>         if (v == 9) {
>           builder.append(romans[i]);
>           builder.append(romans[i - 2]);
>         } else if (v >= 5) {
>           builder.append(romans[i - 1]);
>           builder.append(repeat(romans[i], v-5));
>         } else if (v == 4) {
>           builder.append(romans[i]);
>           builder.append(romans[i - 1]);
>         } else {
>           builder.append(repeat(romans[i], v));
>         }
>         val -= v * divisors[i];
>       }
>     }
>     return builder.toString();
>   }
>
>   private static char[] repeat(char c, int count) {
>     char[] data = new char[count];
>     Arrays.fill(data, c);
>     return data;
>   }
>
>   public static void main(String[] args) {
>     int[] testCases = {1, 4, 5, 6, 8, 9, 10, 11, 13, 14, 15, 30, 32, 36, 39, 125, 234, 345, 456, 567, 678, 789, 890, 891, 900, 901, 912, 1234, 2345, 3456, 1567, 2678, 3789, 2001, 2493, 2587, 3888, 3999};
>     ToRomans s = new ToRomans();
>     for (int test : testCases) {
>       System.out.printf("%4d = %s%n", test, s.intToRoman(test));
>     }
>     test();
>   }
>
>   private static void test() {
>     Map<Integer, String> dataMap = new HashMap<>();
>     load(dataMap, 1, "I");
>     load(dataMap, 4, "IV");
>     load(dataMap, 5, "V");
>     load(dataMap, 6, "VI");
>     load(dataMap, 8, "VIII");
>     load(dataMap, 9, "IX");
>     load(dataMap, 10, "X");
>     load(dataMap, 11, "XI");
>     load(dataMap, 13, "XIII");
>     load(dataMap, 14, "XIV");
>     load(dataMap, 15, "XV");
>     load(dataMap, 30, "XXX");
>     load(dataMap, 32, "XXXII");
>     load(dataMap, 36, "XXXVI");
>     load(dataMap, 39, "XXXIX");
>     load(dataMap, 125, "CXXV");
>     load(dataMap, 234, "CCXXXIV");
>     load(dataMap, 345, "CCCXLV");
>     load(dataMap, 456, "CDLVI");
>     load(dataMap, 567, "DLXVII");
>     load(dataMap, 678, "DCLXXVIII");
>     load(dataMap, 789, "DCCLXXXIX");
>     load(dataMap, 890, "DCCCXC");
>     load(dataMap, 891, "DCCCXCI");
>     load(dataMap, 900, "CM");
>     load(dataMap, 901, "CMI");
>     load(dataMap, 912, "CMXII");
>     load(dataMap, 1234, "MCCXXXIV");
>     load(dataMap, 2345, "MMCCCXLV");
>     load(dataMap, 3456, "MMMCDLVI");
>     load(dataMap, 1567, "MDLXVII");
>     load(dataMap, 2678, "MMDCLXXVIII");
>     load(dataMap, 3789, "MMMDCCLXXXIX");
>     load(dataMap, 2001, "MMI");
>     load(dataMap, 2493, "MMCDXCIII");
>     load(dataMap, 2587, "MMDLXXXVII");
>     load(dataMap, 3888, "MMMDCCCLXXXVIII");
>     load(dataMap, 3999, "MMMCMXCIX");
>     ToRomans toRomans = new ToRomans();
>     for (Integer i: dataMap.keySet()) {
>       String expected = dataMap.get(i);
>       String actual = toRomans.intToRoman(i);
> //      assertEquals(String.valueOf(i), expected, actual);
>       if (!expected.equals(actual)) { // in JUnit, replace this block with the line commented out above.
>         throw new AssertionError(String.format("For %d, expected %s, got %s", i, expected, actual));
>       }
>     }
>   }
>
>   private static void load(Map<Integer, String> map, int i, String result) {
>     map.put(i, result);
>   }
> }
>
> — Miguel Muñoz
> ———
> 4210 Via Arbolada #226Los Angeles, CA 90042
> 323-225-7285
> –
>
> The Sun, with all those planets going around it and dependent on it, can still ripen a vine of grapes like it has nothing else to do in the world.
>   — Galileo
>
>     On Thursday, May 27, 2021, 03:21:09 PM PDT, Thad Guidry <th...@gmail.com> wrote:
>
>  Hello,
>
> I've checked the source of https://commons.apache.org/proper/commons-numbers
> but didn't find support for Roman numeral conversion.
>
> Is this in another project?
> Not at all?
> Planned for Numbers or another subproject like Lang, Text, or Math?
>
> Thad
> https://www.linkedin.com/in/thadguidry/
> https://calendly.com/thadguidry/
>

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