12. Integer to Roman

Seven different symbols represent Roman numerals with the following values:

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

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:

Input: num = 3749

Output: "MMMDCCXLIX"

Explanation:

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:

Input: num = 58

Output: "LVIII"

Explanation:

50 = L
 8 = VIII

Example 3:

Input: num = 1994

Output: "MCMXCIV"

Explanation:

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

Constraints:

• n == height.length
• 2 <= n <= 105
• 0 <= height[i] <= 104

Complexity

• Time complexity: O(n)
• Space complexity: O(1)

Code

class Solution:
    def intToRoman(self, num: int) -> str:
        Roman = ""
        storeIntRoman = [
            [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"],
        ]
        for i in range(len(storeIntRoman)):
            while num >= storeIntRoman[i][0]:
                Roman += storeIntRoman[i][1]
                num -= storeIntRoman[i][0]
        return Roman