LeetCode, leetcodeoj

LeetCode, leetcodeoj

Question:

Given a roman numeral, convert it to an integer.
Input is guaranteed to be within the range from 1 to 3999.

Ideas:

Map the key values, and then the n-1 bits are scanned to The 0th bits.

package manipulation;import java.util.HashMap;public class RomanToInteger {    public int romanToInt(String s) {        int len = 0;        if (s == null || (len = s.length()) == 0) return 0;        HashMap<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 res = map.get(s.charAt(len - 1));        for (int i = len - 2; i >= 0; --i) {            if (map.get(s.charAt(i + 1)) > map.get(s.charAt(i)))                res -= map.get(s.charAt(i));            else                res += map.get(s.charAt(i));        }                return res;    }        public static void main(String[] args) {        // TODO Auto-generated method stub        RomanToInteger r = new RomanToInteger();        System.out.println(r.romanToInt("MCM"));    }}