13_romanToInt.py

# 13. Roman to Integer

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