roman to int

Solution.java

public class Solution {
    
    private static final String seq = "IVXLCDM";


    public int romanToInt(String s) {
		if (null == s || s.length() == 0) {
			return 0;
		}
		
		if (s.length() == 1) {
			return code(s.charAt(0));
		}
		
		String s1 = s.substring(0,1);
		String s2 = s.substring(1,s.length());
				
		return romanToInt(s1, s2);
	}
	
	
	private int romanToInt(String s1, String s2) {
		if (seq.indexOf(s1) < seq.indexOf(s2.charAt(0))) {
			return romanToInt(s2) - code(s1.charAt(0));
		} else {
			return code(s1.charAt(0)) + romanToInt(s2);
		}
	}

	private int code(char c) {
		int tmp = 0;
		switch(c) {
			case 'I':
				tmp = 1;
				break;
			case 'V':
				tmp = 5;
				break;
			case 'X' :
				tmp = 10;
				break;
			case 'L':
				tmp = 50;
				break;
			case 'C':
				tmp = 100;
				break;
			case 'D':
				tmp = 500;
				break;
			case 'M':
				tmp = 1000;
				break;
		}
		return tmp;
	}
}