# Roman to Integer

#1

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

Example 5:

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

#2

Create a map with roman char to their respective int value, do a linear parse of the string, check if the current character is less than the next char in value, if it is deduct it from result, otherwise add it. This takes care of scenarios where `IV`, `IX`, `CM` are in there.

Below Golang code beats 100% of the LC.

``````func romanToInt(s string) int {
result := 0
rmap := map[rune]int{
'I' : 1,
'V' : 5,
'X' : 10,
'L' : 50,
'C' : 100,
'D' : 500,
'M' : 1000,
}

for i:=0;i< len(s)-1; i++{
if rmap[rune(s[i])] < rmap[rune(s[i+1])]{
result -= rmap[rune(s[i])]
} else {
result += rmap[rune(s[i])]
}
}
// add last roman char to result
result += rmap[rune(s[len(s)-1])]

return result
}
``````