## DEV Community Anuj Srivastav

Posted on • Updated on

# Leet Code - Roman Numeral to Integer Function in JavaScript

## Algorithm

• Create a Object for each symbol as key and it's respective
value
```const romanobj = { I : 1, V : 5, X : 10, L : 50, C : 100, D : 500, M : 1000 }```

• Split the Roman Numeral string into Roman Symbols or in different word split string into Characters.

• Take a Symbol from Starting from 0 index
1). If current value of symbol is greater than or equal to
the value of next symbol, then add this value to the
total.
2). else subtract this value by adding the value of next
symbol to the total.

## Javascript Function to Covert Roman Numeral to Integer

``````/**
* @param {string} s
* @return {number}
*/
const obj = {
I      :     1,
V      :     5,
X      :     10,
L      :     50,
C      :     100,
D      :     500,
M      :     1000
}
var romanToInt = function(s) {
let result = 0;
for(let i=0;i<s.length;i++){
if(i+1<s.length){
if(obj[s[i]]>=obj[s[i+1]]){
result = result + obj[s[i]];

}else{
result = result + obj[s[i+1]]-obj[s[i]];
i++;
}
}else{
result = result + obj[s[i]];
}
}
return result;

};
``````

## Test Cases

```Input: s = "III" Output: 3 Explanation: III = 3.```

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

We are so used to reading from Left to Right, we overlook the Right to Left alternatives.

The whole point of Roman notation is you want to check if I becomes before X

That is much easier when you reverse the Roman string.

Or in JavaScript, use the hardly ever used `reduceRight` method

(code optimized for best GZIP/Brotli compression)