# 13. Roman to Integer

## 15 Dec 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]`.
class Solution:
def romanToInt(self, s: str) -> int:
conversations = {
“I”:1,
“V”:5,
“X”:10,
“L”:50,
“C”:100,
“D”:500,
“M”:1000
}

result = 0
s = s.replace(“IV”, “IIII”).replace(“IX”,”VIIII”)
s = s.replace(“XL”, “XXXX”).replace(“XC”,”LXXXX”)
s = s.replace(“CD”, “CCCC”).replace(“CM”,”DCCCC”)
print(s)

for char in s:
result = result + conversations[char]
print(conversations[char])
print(result)
return result
class Solution:
def romanToInt(self, s: str) -> int:
conversations = {
“I”:1,
“V”:5,
“X”:10,
“L”:50,
“C”:100,
“D”:500,
“M”:1000
}

result = 0
previous = 0
for char in s[::-1]:
# from last to first
current = conversations[char]
if current >= previous :
result = result + current
else:
result = result – current
previous = current
print(“char:”+str(char))
print(“current:”+str(current))
print(“result:”+str(result))
return result