13_Roman_to_Integer.py

class Solution:
    def romanToInt(self, s: str) -> int:
        num = 0
        i = 0
        while i < len(s):
            if s[i] == 'M':
                num +=1000
            elif s[i] == 'D':
                num += 500
            elif s[i] == 'C':
                if i+1 != len(s):
                    if s[i+1] == 'D':
                        num += 400
                        i +=2
                        continue
                    elif s[i+1] == 'M':
                        num += 900
                        i += 2
                        continue
                num += 100
            elif s[i] == 'L':
                num += 50
            elif s[i] == 'X':
                if i+1 != len(s):
                    if s[i+1] == 'C':
                        num += 90
                        i += 2
                        continue
                    elif s[i+1] == 'L':
                        num += 40
                        i += 2
                        continue
                num += 10
            elif s[i] == 'V':
                num += 5
            elif s[i] == 'I':
                if i+1 != len(s):
                    if s[i+1] == 'X':
                        num += 9
                        i+=2
                        continue
                    elif s[i+1] == 'V':
                        num += 4
                        i += 2
                        continue
                num += 1
            
            i += 1
        return num