題目如下：

Given a roman numeral, convert it to an integer.

Input is guaranteed to be within the range from 1 to 3999.

    public int romanToInt(String s) {
        HashMap<String,Integer> map = new HashMap<String,Integer>();
        map.put("I",1);
        map.put("V",5);
        map.put("X",10);
        map.put("C",100);
        map.put("M",1000);
        map.put("L",50);
        map.put("D",500);
        int result = 0;
        for(int i=0;i<s.length();i++){
            int current = map.get(s.charAt(i)+"").intValue();
            if(i<s.length()-1){
                int next = map.get(s.charAt(i+1)+"").intValue();
                result += next>current?current*(-1):current;
            }else{
                result += current;
            }
        }
        return result;
    }