leetcode-13-java

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

Example 1:

Input: "III"
Output: 3
Example 2:

Input: "IV"
Output: 4

class Solution {
     private static Map<String, Integer> doubleMap = new HashMap<String, Integer>() {{
        put("CM", 900);
        put("CD", 400);
        put("XC", 90);
        put("XL", 40);
        put("IX", 9);
        put("IV", 4);
    }};


    private static Map<String, Integer> singleMap = new HashMap<String, Integer>() {{
        put("M", 1000);
        put("D", 500);
        put("C", 100);
        put("L", 50);
        put("X", 10);
        put("V", 5);
        put("I", 1);
    }};


    public static int romanToInt(String s) {
        if (null == s || s.length() == 0) {
            return 0;
        }

        int sum = 0;
        int index = 0;
        while (index < s.length()) {
            int end = index + 2;
            if (end <= s.length()) {
                String douStr = s.substring(index, end);
                if (null != doubleMap.get(douStr)) {
                    sum += doubleMap.get(douStr);
                    index += 2;
                    continue;
                }
            }

            end = index + 1;
            String douStr = s.substring(index, end);
            if (null != singleMap.get(douStr)) {
                sum += singleMap.get(douStr);
                index += 1;
                continue;
            } 
        }
        return sum;
    }
}