## Problem Statement

Roman numerals are represented by seven different symbols: `I`

, `V`

, `X`

, `L`

, `C`

, `D`

and `M`

.

SymbolValueI 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 more numbers,

`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:58Explanation:L = 50, V= 5, III = 3.

**Example 5:**

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

**Solution:**

class Solution:
def romanToInt(self, s: str) -> int:
if not s: return s
transform = {
'I': 1,
'V': 5,
'X': 10,
'L': 50,
'C':100,
'D': 500,
'M': 1000
}
result = 0
for i in range(len(s)):
if i<len(s)-1 and transform[s[i]]<transform[s[i+1]]:
#subtract
result-=transform[s[i]]
else:
result+=transform[s[i]]
return result