Interview Question Integer To Roman

By Fatih KABAKCI

The problem is to convert an integer value which is defined between 1 and 3999, to roman value.

Problem #12 - Integer To Roman

Description: Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999.

Difficulty: Medium

Solution in Java

Reference Roman Table

package com.fatihkabakci.Medium.IntegerToRoman;
/**
 * 
 * @author fkabakci
 * 
 * Problem Description: Given an integer, convert it to a roman numeral. 
 * Input is guaranteed to be within the range from 1 to 3999.
 * 
 * Solution:
 * 
 * Precondition: num is within the range from 1 to 3999
 * 
 * 1. Decrease num as its defined maximum roman value while it is higher than 0.
 */

public class IntegerToRoman {
	public String intToRoman(int num) {
		String x = new String();
		while(num > 0) {
			if(num >= 1000) {
				x += "M";
				num -= 1000;
			}else if(num >= 900) {
				x += "CM";
				num -= 900;
			}else if(num >= 500) {
				x += "D";
				num -= 500;
			}else if(num >= 400) {
				x += "CD";
				num -= 400;
			}else if(num >= 100) {
				x += "C";
				num -= 100;
			}else if(num >= 90) {
				x += "XC";
				num -= 90;
			}else if(num >= 50) {
				x += "L";
				num -= 50;
			}else if(num >= 40) {
				x += "XL";
				num -= 40;
			}else if(num >= 10) {
				x += "X";
				num -= 10;
			}else if(num >= 9) {
				x += "IX";
				num -= 9;
			}else if(num >= 5) {
				x += "V";
				num -= 5;
			}else if(num >= 4) {
				x += "IV";
				num -= 4;
			}else if(num >= 1) {
				x += "I";
				num -= 1;
			}
		}
		return x;
    }
	
	public static void main(String[] args) {
		IntegerToRoman itr = new IntegerToRoman();
		for(int i = 1; i < 3999; i++)
			System.out.println(itr.intToRoman(i));
	}
}

Shorter Solution in Java by the member Fabrizio3

public static String intToRoman(int num) {
    String M[] = {"", "M", "MM", "MMM"};
    String C[] = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"};
    String X[] = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"};
    String I[] = {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"};
    return M[num/1000] + C[(num%1000)/100] + X[(num%100)/10] + I[num%10];
}

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