package Conversions;

import java.util.*;

public class RomanToInteger {

 private static Map<Character, Integer> map = new HashMap<Character, Integer>() {
 /**
 *
 */
 private static final long serialVersionUID = 87605733047260530L;

 {
 put('I', 1);
 put('V', 5);
 put('X', 10);
 put('L', 50);
 put('C', 100);
 put('D', 500);
 put('M', 1000);
 }};
 //Roman Number = Roman Numerals

 /**
 * This function convert Roman number into Integer
 *
 * @param A Roman number string
 * @return integer
 */
 public static int romanToInt(String A) {

 A = A.toUpperCase();
 char prev = ' ';

 int sum = 0;

 int newPrev = 0;
 for (int i = A.length() - 1; i >= 0; i--) {
 char c = A.charAt(i);

 if (prev != ' ') {
 // checking current Number greater then previous or not
 newPrev = map.get(prev) > newPrev ? map.get(prev) : newPrev;
 }

 int currentNum = map.get(c);

 // if current number greater then prev max previous then add
 if (currentNum >= newPrev) {
 sum += currentNum;
 } else {
 // subtract upcoming number until upcoming number not greater then prev max
 sum -= currentNum;
 }

 prev = c;
 }

 return sum;
 }

 public static void main(String[] args) {
 int sum = romanToInt("MDCCCIV");
 System.out.println(sum);
 }
}