Integer to Roman

Problem

Given an integer num, convert it to a Roman numeral.

Here is the Roman numerals chart for reference:

• I 1
• V 5
• X 10
• L 50
• C 100
• D 500
• M 1000

In addition, the Roman numeral system has some special rules:

1. I can be placed before V (5) and X (10) to make 4 and 9.
2. X can be placed before L (50) and C (100) to make 40 and 90.
3. C can be placed before D (500) and M (1000) to make 400 and 900.

Examples

integerToRoman(3) 
// returns "III"
// 3 represents the Roman numeral III.

integerToRoman(4)
// returns "IV"
// 4 represents the Roman numeral IV.

integerToRoman(9)
// returns "IX"
// 9 represents the Roman numeral IX.