class Solution {
    public int romanToInt(String s) {
        HashMap<String, Integer> lookupMap = new HashMap<>();
        lookupMap.put("I", 1);
        lookupMap.put("V", 5);
        lookupMap.put("X", 10);
        lookupMap.put("L", 50);
        lookupMap.put("C", 100);
        lookupMap.put("D", 500);
        lookupMap.put("M", 1000);

        int runningCount = 0;
        char previous = ' ';

        for (char c : s.toCharArray()) {
            int currentVal = lookupMap.get(Character.toString(c));
            runningCount += currentVal;
            if ((previous == 'I')&&((c=='V')||(c=='X'))){
                runningCount -=2;
            } else if ((previous == 'X')&&((c=='L')||(c=='C'))){
                runningCount -= 20;
            } else if ((previous == 'C')&&((c=='D')||(c=='M'))){
                runningCount -= 200;
            }
            previous = c;

        }
        return runningCount;
    }
}