Write a function to convert an integer into its roman numeral representation - Java Algorithm

Java examples for Algorithm:Number

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Description

Write a function to convert an integer into its roman numeral representation

Demo Code


public class IntToRoman {
    // Parallel arrays of numerals in descending order and their values. We 
    // include any pairs of numerals where a smaller numeral is subtracted from
    // a larger numeral
    private static final String[] numerals = new String[] { "M", "CM", "D",
            "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I" };
    private static final int[] values = new int[] { 1000, 900, 500, 400,
            100, 90, 50, 40, 10, 9, 5, 4, 1 };

    public static String integerToRoman(int value) {
        // We are only considering the range for standard roman numerals
        if (value > 3999 || value < 1)
            throw new IllegalArgumentException();

        StringBuilder numeral = new StringBuilder();
        int i = 0;
        // Greedily append the largest numeral possible until the value is 0
        while (value > 0) {
            if (value - values[i] >= 0) {
                numeral.append(numerals[i]);
                value -= values[i];/*from   ww w  .j a va2  s  .  com*/
            } else {
                i++;
            }
        }

        return numeral.toString();
    }

    // Sample test cases
    public static void main(String[] args) {
        assert integerToRoman(1).equals("I");
        assert integerToRoman(4).equals("IV");
        assert integerToRoman(6).equals("VI");
        assert integerToRoman(11).equals("XI");
        assert integerToRoman(49).equals("XLIX");
        assert integerToRoman(2020).equals("MMXX");

    }
}

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