12.IntegertoRoman.py

'''
    Roman numerals are represented by seven different symbols: 
    I, V, X, L, C, D and M.

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

    For example, 2 is written as II in Roman numeral, just two 
    one's added together. 12 is written as XII, which is simply 
    X + II. The number 27 is written as XXVII, which is 
    XX + V + II.

    Roman numerals are usually written largest to smallest from 
    left to right. However, the numeral for four is not IIII. 
    Instead, the number four is written as IV. Because the one 
    is before the five we subtract it making four. The same 
    principle applies to the number nine, which is written as IX. 
    There are six instances where subtraction is used:

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

    Given an integer, convert it to a roman numeral.

    Example:
    Input: num = 3
    Output: "III"

    Example:
    Input: num = 4
    Output: "IV"

    Example:
    Input: num = 9
    Output: "IX"

    Example:
    Input: num = 58
    Output: "LVIII"
    Explanation: L = 50, V = 5, III = 3.

    Example:
    Input: num = 1994
    Output: "MCMXCIV"
    Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.

    Constraints:
        - 1 <= num <= 3999
'''
#Difficulty: Medium
#3999 / 3999 test cases passed.
#Runtime: 48 ms
#Memory Usage: 14.2 MB

#Runtime: 48 ms, faster than 65.88% of Python3 online submissions for Integer to Roman.
#Memory Usage: 14.2 MB, less than 66.85% of Python3 online submissions for Integer to Roman.

class Solution:
    def intToRoman(self, num: int) -> str:
        y = 10
        roman = ''
        nums = {1: 'I',  2: 'II', 3: 'III', 4: 'IV', 5: 'V', 
                6: 'VI', 7: 'VII', 8: 'VIII', 9: 'IX',
                10: 'X', 20: 'XX', 30: 'XXX', 40: 'XL', 50: 'L', 
                60: 'LX', 70: 'LXX', 80: 'LXXX', 90: 'XC',
                100: 'C', 200: 'CC', 300: 'CCC', 400: 'CD', 
                500: 'D', 600: 'DC', 700: 'DCC', 800: 'DCCC', 
                900: 'CM', 1000: 'M', 2000: 'MM', 3000: 'MMM'}
        while num:
            x = num % y
            num -= x
            y *= 10
            if x:
                roman = nums[x] + roman
        return roman