leetcode/problems/0012-py/main.py at main · emfomy/leetcode · GitHub

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# Source: https://leetcode.com/problems/integer-to-roman
# Title: Integer to Roman
# Difficulty: Medium
# Author: Mu Yang <http://muyang.pro>

################################################################################################################################
# # 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 appendingthe conversions ofdecimal place valuesfrom highest to lowest. Converting a decimal place value into a Roman numeral has the following rules:
#
# - If the value does not start with 4 or9, 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**representingone 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 symbol4 timesuse 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:**
#
# - `1 <= num <= 3999`
#
################################################################################################################################


class Solution:
    def intToRoman(self, num: int) -> str:
        romans0 = ["", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"]
        romans1 = ["", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"]
        romans2 = ["", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"]
        romans3 = ["", "M", "MM", "MMM"]

        num0 = num % 10
        num1 = (num // 10) % 10
        num2 = (num // 100) % 10
        num3 = (num // 1000) % 10

        return romans3[num3] + romans2[num2] + romans1[num1] + romans0[num0]