13. Roman to Integer

13. Roman to Integer

 

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 ones 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 a roman numeral, convert it to an integer.

 

Example 1:

Input: s = "III"
Output: 3
Explanation: III = 3.

Example 2:

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

Example 3:

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

 

Constraints:

• 1 <= s.length <= 15
• s contains only the characters ('I', 'V', 'X', 'L', 'C', 'D', 'M').
• It is guaranteed that s is a valid roman numeral in the range [1, 3999].

2. 풀이

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

 

3. 해설

 

이것은 구현 문제이다.

 

먼저 Roma 숫자를 딕셔너리에 담는다.

이후에 for문 돌려가며 

뒤의 숫자보다 앞에가 크면 더해주고 반대면 빼주면 된다.