Q12: (M) Int to Roman

class Solution {

    private HashMap<Integer, String> intToRomanMap = new HashMap<Integer, String>();

    public String intToRoman(int num) {
        intToRomanMap.put(1, "I");
        intToRomanMap.put(5, "V");
        intToRomanMap.put(10, "X");
        intToRomanMap.put(50, "L");
        intToRomanMap.put(100, "C");
        intToRomanMap.put(500, "D");
        intToRomanMap.put(1000, "M");

        StringBuilder sb = new StringBuilder();

        char[] digitCharArr = Integer.toString(num).toCharArray();
        int[] digitArr = new int[digitCharArr.length];
        for(int i=0; i<digitArr.length; i++) { digitArr[i] = Character.getNumericValue(digitCharArr[i]); }

        for(int i=digitArr.length-1; i>=0; i--) { sb.append(processDigit(i, digitArr));}

        return sb.toString();
    }

    private String processDigit(int digitPlace, int[] digitArr) {
        StringBuilder sb = new StringBuilder();
        if(digitArr[(digitArr.length-1) - digitPlace] == 9) {
            sb.append(intToRomanMap.get((int)Math.pow(10, digitPlace)));
            sb.append(intToRomanMap.get((int)Math.pow(10, digitPlace+1)));
        }
        else if(5 <= digitArr[(digitArr.length-1) - digitPlace] && digitArr[(digitArr.length-1) - digitPlace] <= 8) {
            sb.append(intToRomanMap.get(5 * (int)Math.pow(10, digitPlace)));
            int remainingValue = digitArr[(digitArr.length-1) - digitPlace] - 5;
            for(int i=1; i<=remainingValue; i++) { sb.append(intToRomanMap.get((int)Math.pow(10, digitPlace))); }
        }
        else if(digitArr[(digitArr.length-1) - digitPlace] == 4) {
            sb.append(intToRomanMap.get((int)Math.pow(10, digitPlace)));
            sb.append(intToRomanMap.get(5 * (int)Math.pow(10, digitPlace)));
        }
        else 
            for(int i=1; i<=digitArr[(digitArr.length-1) - digitPlace]; i++) { sb.append(intToRomanMap.get((int)Math.pow(10, digitPlace))); }

        return sb.toString();
    }

}