012-integer-to-roman

Question

https://leetcode.com/problems/integer-to-roman/description/

Given an integer, convert it to a roman numeral.

Input is guaranteed to be within the range from 1 to 3999.

Example:

Thought Process

1. Char Table and Int Table
   1. For every divisor, from 1000 to 1, we check the quotient and decide appropriate character to append
   2. Time complexity O(n), where n is number of divisor
   3. Space complexity O(n)
2. Char Table
   1. Time complexity O(d), where d is number of digits
   2. Space complexity O(d)

Solution

class Solution {
    public char[] createCharTable(){
        char[] table = new char[] {'M', 'D', 'C', 'L', 'X', 'V', 'I'};
        return table;
    }

    public int[] createIntTable(){
        int[] table = new int[] {1000, 500, 100, 50, 10, 5, 1};
        return table;
    }

    public String intToRoman(int num) {
        char[] charTable = createCharTable();
        int[] intTable = createIntTable();
        StringBuilder sb = new StringBuilder();
        for(int i = 0; i < intTable.length; i+=2){
            int k = num / intTable[i];
            if(k >= 10){
                return "";
            } else if (k == 9){
                sb.append(charTable[i]);
                sb.append(charTable[i-2]);
            } else if (k >= 5){
                sb.append(charTable[i-1]);
                for(int j = 5; j < k; j++) sb.append(charTable[i]);
            } else if (k == 4){
                sb.append(charTable[i]);
                sb.append(charTable[i-1]);
            } else {
                for(int j = 0; j < k; j++) sb.append(charTable[i]);
            }
            num %= intTable[i];
        }
        return sb.toString();
    }
}

class Solution {
    public String intToRoman(int num) {
        String M[] = {"", "M", "MM", "MMM"};
        String C[] = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"};
        String X[] = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"};
        String I[] = {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"};
        return M[num/1000] + C[(num%1000)/100] + X[(num%100)/10] + I[num%10];
    }
}

Additional