LeetCode - 13번 Roman to Integer

LeetCode 13번 Roman to Integer

문제

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, two is written as II in Roman numeral, just two one’s added together. Twelve is written as, XII, which is simply X + II. The number twenty seven 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 a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.

Example 1

Input: "III"
Output: 3

Example 2

Input: "IV"
Output: 4

Example 3

Input: "IX"
Output: 9

Example 4

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

Example 5

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

내 풀이

class Solution:
  def romanToInt(self, s: str) -> int:
    rome = {
      'I': 1,
      'V': 5,
      'X': 10,
      'L': 50,
      'C': 100,
      'D': 500,
      'M': 1000
    }
    result = 0
    for i in range(len(s)):
      if i > 0 and rome[s[i]] > rome[s[i-1]]:
        result += rome[s[i]] - (2*rome[s[i-1]])
      else:
        result += rome[s[i]]
    return result

처음에는 로마자 리스트 따로, 숫자 리스트 따로 해서 인덱스 값으로 찾아서 뭐 어떻게 해볼 수 있지 않을까 생각했다. 이렇게.

rome = ['I', 'V', 'X', 'L', 'C', 'D', 'M']
nums = [1, 5, 10, 50, 100, 500, 1000]

for i in s:
  idx = rome.index(i)
  value = nums[idx]

뭐 이렇게 하면 인풋 로마자 개별에 해당하는 integer값을 찾을 수 있을 거긴 한데, 그 다음에는 어떻게…어떻게 하지… 미궁에 빠져서 헤매다 답을 찾아봤다. 울적하다.