C1_78_RomaIntegerConverter.java

package com.interview.algorithms.general;

import java.util.Hashtable;

/**
 * Created_By: stefanie
 * Date: 14-11-7
 * Time: 下午10:42
 */
public class C1_78_RomaIntegerConverter {
    static Hashtable<Character,Integer> map = new Hashtable<Character,Integer>();
    static {
        map.put('M', 1000);
        map.put('D', 500);
        map.put('C', 100);
        map.put('L', 50);
        map.put('X', 10);
        map.put('V', 5);
        map.put('I', 1);
    }

    static int[] weights={1000,900,500,400,100,90,50,40,10,9,5,4,1};
    static String[] tokens={"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};

    public static int roma2int(String roma){
        int sum=0;
        for(int i = 0; i < roma.length(); i++){
            if(i < roma.length() - 1 && map.get(roma.charAt(i)) < map.get(roma.charAt(i+1)))
                sum-= map.get(roma.charAt(i));
            else
                sum+= map.get(roma.charAt(i));
        }
        return sum;
    }

    public static String int2rome(int num){
        StringBuilder builder = new StringBuilder();
        int start = 0;
        while(num > 0){
            for(int i = start; i < 13; i++){
                if(num >= weights[i]){
                    num -= weights[i];
                    builder.append(tokens[i]);
                    break;
                }
                start= i + 1; // skip those impossible check, make it faster
            }
        }
        return builder.toString();
    }
}