roman_2_integer.java

import java.util.Scanner;

/**
 * Created by xynophon on 15.1.27.
 */

public class roman_2_integer{

// I 1
// IV 4
// V 5
// IX 9
// X 10
// XL 40
// L 50
// XC 90
// C 100
// D 500
// M 1000

// MCMXCIX 1999

// I X C M
// IV 4, IX 9, XL 40, XC 90, CD 400, CM 900


    public int char_2_num(char cha){
        if(cha == 'I')return 1;
        else if(cha == 'V')return 5;
        else if(cha == 'X')return 10;
        else if(cha == 'L')return 50;
        else if(cha == 'C')return 100;
        else if(cha == 'D')return 500;
        else return 1000;
    }

    public int solution(String s){
        int num = 0;
        for(int i = 0; i < s.length(); i++){
            num += char_2_num(s.charAt(i));
            System.out.print(s.charAt(i)+" ");
            if(i >= 1) {
                if (s.charAt(i) == 'V' || s.charAt(i) == 'X') {
                    if (s.charAt(i - 1) == 'I') {
                        num -= 2*char_2_num(s.charAt(i - 1));
                    }
                } else if (s.charAt(i) == 'L' || s.charAt(i) == 'C') {
                    if (s.charAt(i - 1) == 'X') {
                        num -= 2*char_2_num(s.charAt(i - 1));
                    }
                } else if (s.charAt(i) == 'D' || s.charAt(i) == 'M') {
                    if (s.charAt(i - 1) == 'C') {
                        num -= 2*char_2_num(s.charAt(i - 1));
                    }
                }
            }
        }
        return num;
    }


    public static void main (String args[]){
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        roman_2_integer ri = new roman_2_integer();
        System.out.println(ri.solution(line));
    }

}