Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999. ~~~ public class Solution { public int romanToInt(String s) { Map<Character, Integer> map = new HashMap<Character, Integer>(); map.put('I', 1); map.put('V', 5); map.put('X', 10); map.put('L', 50); map.put('C', 100); map.put('D', 500); map.put('M', 1000); int result = 0; for (int i = 0; i < s.length(); i++) { char ch = s.charAt(i); if (i == 0) { result += map.get(ch); } else { char prev = s.charAt(i - 1); if (map.get(ch) > map.get(prev)) { result += map.get(ch); result -= map.get(prev) * 2; } else { result += map.get(ch); } } } return result; } } ~~~