Coding Challenge Practice - Question 70

The task is to implement a function that converts Roman numerals to integers.

The boilerplate code:

function romanToInteger(str) {
  // your code here
}

The letters representing numbers in the Roman numeral system are seven in number.

const map = {
I: 1,
V: 5,
X: 10,
L: 50,
C: 100,
D: 500,
M: 1000

}

Roman numerals usually add numbers together (X + V = 15). The only exception being when the next number is bigger than the previous one, i.e IV, IX. In that case, one is subtracted from the bigger number.

for (let i = 0; i < str.length; i++) {
    let curr = map[str[i]];
    let next = map[str[i + 1]];

    if (next > curr) {
      result -= curr;
    } else {
      result += curr;
    }

Curr is the numeral being checked, while next is the number beside it which is checked to see if it is bigger.

The final code:

function romanToInteger(str) {
  // your code here
  const map = {
    I: 1,
    V: 5,
    X: 10,
    L: 50,
    C: 100,
    D: 500,
    M: 1000
  }
  let result = 0;

  for(let i = 0; i < str.length; i++) {
    let curr = map[str[i]];
    let next = map[str[i + 1]];

    if(next > curr) {
      result -= curr;
    } else {
      result += curr;
    }
  }
  return result
}

That's all folks!