diff --git a/src/main/java/com/thealgorithms/conversions/IntegerToRoman.java b/src/main/java/com/thealgorithms/conversions/IntegerToRoman.java index 9c031df95..fec437668 100644 --- a/src/main/java/com/thealgorithms/conversions/IntegerToRoman.java +++ b/src/main/java/com/thealgorithms/conversions/IntegerToRoman.java @@ -1,68 +1,68 @@ package com.thealgorithms.conversions; /** - * Converting Integers into Roman Numerals + * A utility class to convert integers into Roman numerals. * - *

- * ('I', 1); ('IV',4); ('V', 5); ('IX',9); ('X', 10); ('XL',40); ('L', 50); - * ('XC',90); ('C', 100); ('D', 500); ('M', 1000); + *

Roman numerals follow these rules: + *

+ * + *

Conversion is based on repeatedly subtracting the largest possible Roman numeral value + * from the input number until it reaches zero. For example, 1994 is converted as: + *

+ *   1994 -> MCMXCIV (1000 + 900 + 90 + 4)
+ * 
*/ public final class IntegerToRoman { + + // Array of Roman numeral values in descending order + private static final int[] ALL_ROMAN_NUMBERS_IN_ARABIC = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1}; + + // Corresponding Roman numeral symbols + private static final String[] ALL_ROMAN_NUMBERS = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"}; + private IntegerToRoman() { } - private static final int[] ALL_ROMAN_NUMBERS_IN_ARABIC = new int[] { - 1000, - 900, - 500, - 400, - 100, - 90, - 50, - 40, - 10, - 9, - 5, - 4, - 1, - }; - private static final String[] ALL_ROMAN_NUMBERS = new String[] { - "M", - "CM", - "D", - "CD", - "C", - "XC", - "L", - "XL", - "X", - "IX", - "V", - "IV", - "I", - }; - - // Value must be > 0 + /** + * Converts an integer to its Roman numeral representation. + * Steps: + *
    + *
  1. Iterate over the Roman numeral values in descending order
  2. + *
  3. Calculate how many times a numeral fits
  4. + *
  5. Append the corresponding symbol
  6. + *
  7. Subtract the value from the number
  8. + *
  9. Repeat until the number is zero
  10. + *
  11. Return the Roman numeral representation
  12. + *
+ * + * @param num the integer value to convert (must be greater than 0) + * @return the Roman numeral representation of the input integer + * or an empty string if the input is non-positive + */ public static String integerToRoman(int num) { if (num <= 0) { return ""; } StringBuilder builder = new StringBuilder(); - - for (int a = 0; a < ALL_ROMAN_NUMBERS_IN_ARABIC.length; a++) { - int times = num / ALL_ROMAN_NUMBERS_IN_ARABIC[a]; - for (int b = 0; b < times; b++) { - builder.append(ALL_ROMAN_NUMBERS[a]); - } - - num -= times * ALL_ROMAN_NUMBERS_IN_ARABIC[a]; + for (int i = 0; i < ALL_ROMAN_NUMBERS_IN_ARABIC.length; i++) { + int times = num / ALL_ROMAN_NUMBERS_IN_ARABIC[i]; + builder.append(ALL_ROMAN_NUMBERS[i].repeat(Math.max(0, times))); + num -= times * ALL_ROMAN_NUMBERS_IN_ARABIC[i]; } return builder.toString(); } - - public static void main(String[] args) { - System.out.println(IntegerToRoman.integerToRoman(2131)); - } } diff --git a/src/test/java/com/thealgorithms/conversions/IntegerToRomanTest.java b/src/test/java/com/thealgorithms/conversions/IntegerToRomanTest.java index 04768d034..181cad930 100644 --- a/src/test/java/com/thealgorithms/conversions/IntegerToRomanTest.java +++ b/src/test/java/com/thealgorithms/conversions/IntegerToRomanTest.java @@ -10,5 +10,30 @@ public class IntegerToRomanTest { public void testIntegerToRoman() { assertEquals("MCMXCIV", IntegerToRoman.integerToRoman(1994)); assertEquals("LVIII", IntegerToRoman.integerToRoman(58)); + assertEquals("IV", IntegerToRoman.integerToRoman(4)); + assertEquals("IX", IntegerToRoman.integerToRoman(9)); + assertEquals("MMM", IntegerToRoman.integerToRoman(3000)); + } + + @Test + public void testSmallNumbers() { + assertEquals("I", IntegerToRoman.integerToRoman(1)); + assertEquals("II", IntegerToRoman.integerToRoman(2)); + assertEquals("III", IntegerToRoman.integerToRoman(3)); + } + + @Test + public void testRoundNumbers() { + assertEquals("X", IntegerToRoman.integerToRoman(10)); + assertEquals("L", IntegerToRoman.integerToRoman(50)); + assertEquals("C", IntegerToRoman.integerToRoman(100)); + assertEquals("D", IntegerToRoman.integerToRoman(500)); + assertEquals("M", IntegerToRoman.integerToRoman(1000)); + } + + @Test + public void testEdgeCases() { + assertEquals("", IntegerToRoman.integerToRoman(0)); // Non-positive number case + assertEquals("", IntegerToRoman.integerToRoman(-5)); // Negative number case } }