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, 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.
[입력 조건]
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].
[내 풀이]
class Solution:
def romanToInt(self, s: str) -> int:
mapping = {"I":1,"V":5,"X":10,"L":50,"C":100,"D":500,"M":1000,"IV":4,"IX":9,"XL":40,"XC":90,"CD":400,"CM":900}
i = 0
result = 0
while i < len(s):
if i < len(s)-1 and s[i:i+2] in mapping:
result += mapping[s[i:i+2]]
i += 2
else:
result += mapping[s[i]]
i += 1
return result
각 로마 숫자 문자에 해당하는 값을 미리 매핑하여 사용합니다.
그리고 문자열을 순회하면서 현재 문자와 다음 문자를 함께 검사하여, 두 문자가 사전에 있는 값이라면 해당 값을 더합니다.
이를 통해 예를 들어 'IV', 'IX'와 같이 두 문자가 함께 처리되어야 하는 로마 숫자도 쉽게 처리할 수 있습니다.
그렇지 않은 경우에는 현재 문자만 처리합니다.
[출처]
https://leetcode.com/problems/roman-to-integer/description/
