Integer to Roman

Problem Description

Seven different symbols represent Roman numerals with the following values:

Roman numerals are formed by appending the conversions of decimal place values from highest to lowest. Converting a decimal place value into a Roman numeral has the following rules:

• If the value does not start with 4 or 9, select the symbol of the maximal value that can be subtracted from the input, append that symbol to the result, subtract its value, and convert the remainder to a Roman numeral.
• If the value starts with 4 or 9 use the subtractive form representing one symbol subtracted from the following symbol, for example, 4 is 1 (I) less than 5 (V): IV and 9 is 1 (I) less than 10 (X): IX. Only the following subtractive forms are used: 4 (IV), 9 (IX), 40 (XL), 90 (XC), 400 (CD) and 900 (CM).
• Only powers of 10 (I, X, C, M) can be appended consecutively at most 3 times to represent multiples of 10. You cannot append 5 (V), 50 (L), or 500 (D) multiple times. If you need to append a symbol 4 times use the subtractive form.

Given an integer, convert it to a Roman numeral.

Example 1:

3000 = MMM as 1000 (M) + 1000 (M) + 1000 (M)
 700 = DCC as 500 (D) + 100 (C) + 100 (C)
  40 = XL as 10 (X) less of 50 (L)
   9 = IX as 1 (I) less of 10 (X)
Note: 49 is not 1 (I) less of 50 (L) because the conversion is based on decimal places

Example 2:

50 = L
 8 = VIII

Example 3:

1000 = M
 900 = CM
  90 = XC
   4 = IV

Constraints:

• 1 <= num <= 3999

Solution (JavaScript)

/**
 * @param {number} num
 * @return {string}
 */
var intToRoman = function(num) {
    var romanMatrix = [
      [1000, 'M'],
      [900, 'CM'],
      [500, 'D'],
      [400, 'CD'],
      [100, 'C'],
      [90, 'XC'],
      [50, 'L'],
      [40, 'XL'],
      [10, 'X'],
      [9, 'IX'],
      [5, 'V'],
      [4, 'IV'],
      [1, 'I']
    ];
    
    var rom = '';
    for (var i = 0; i < romanMatrix.length; i++ ) {
        rom += romanMatrix[i][1].repeat(Math.floor(num/romanMatrix[i][0]));
        num = num % romanMatrix[i][0];
    }
    
    return rom;
};